@article{wells_aguilos_huang_gao_hou_huang_liao_lin_zhao_qiu_et al._2023, title={Attributing interannual variability of net ecosystem exchange to modeled ecological processes in forested wetlands of contrasting stand age}, volume={9}, ISSN={["1572-9761"]}, DOI={10.1007/s10980-023-01768}, journal={LANDSCAPE ECOLOGY}, author={Wells, Jon M. and Aguilos, Maricar and Huang, Xin and Gao, Yuan and Hou, Enqing and Huang, Wenjuan and Liao, Cuijuan and Lin, Lin and Zhao, Ruiying and Qiu, Han and et al.}, year={2023}, month={Sep} }
 @article{wells_aguilos_huang_gao_hou_huang_liao_lin_zhao_qiu_et al._2023, title={Attributing interannual variability of net ecosystem exchange to modeled ecological processes in forested wetlands of contrasting stand age}, volume={38}, ISSN={0921-2973 1572-9761}, url={http://dx.doi.org/10.1007/s10980-023-01768-x}, DOI={10.1007/s10980-023-01768-x}, number={12}, journal={Landscape Ecology}, publisher={Springer Science and Business Media LLC}, author={Wells, Jon M. and Aguilos, Maricar and Huang, Xin and Gao, Yuan and Hou, Enqing and Huang, Wenjuan and Liao, Cuijuan and Lin, Lin and Zhao, Ruiying and Qiu, Han and et al.}, year={2023}, month={Sep}, pages={3985–3998} }
 @article{fischer_katul_noormets_poznikova_domec_orsag_zalud_trnka_king_2023, title={Merging flux-variance with surface renewal methods in the roughness sublayer and the atmospheric surface layer}, volume={342}, ISSN={["1873-2240"]}, DOI={10.1016/j.agrformet.2023.109692}, abstractNote={Two micrometeorological methods utilizing high-frequency sampled air temperature were tested against eddy covariance (EC) sensible heat flux (H) measurements at three sites representing agricultural, agro-forestry, and forestry systems. The two methods cover conventional and newly proposed forms of the flux-variance (FV) and surface renewal (SR) schemes of differing complexities. The sites represent measurements in surface, roughness, and roughness to surface transitional layers. Regression analyzes against EC show that the most reliable FV and SR forms estimate H with slopes within ±10% from unity and coefficient of determination R2>0.9 across all the three sites. The best performance of both FV and SR was found at the agricultural site with measurements well within the surface layer, while the worst was found for the tall forest with measurements within the roughness sublayer where its thickness needed to be additionally estimated. The main variable driving H in FV is the temperature variance, whereas in SR, it is the geometry of ramp-like structures. Since these structures are also responsible for most of the temperature variance, a novel FV-SR approach emerging from combining the methods is proposed and evaluated against EC measurements and conventional FV and SR schemes. The proposed FV-SR approach requiring only a single fast response thermocouple is potentially independent of calibration and ameliorates some of the theoretical objections that arise when combining ramp statistics with similarity arguments. The combination of methods also provides new insights into the contribution of coherent structures to the temperature variance and its dependence on atmospheric stratification. Other potential utility of the new method is to include it in multi-tool assessments of surface energy fluxes, since a convergence or divergence of the results has a high diagnostic value.}, journal={AGRICULTURAL AND FOREST METEOROLOGY}, author={Fischer, Milan and Katul, Gabriel and Noormets, Asko and Poznikova, Gabriela and Domec, Jean-Christophe and Orsag, Matej and Zalud, Zdenek and Trnka, Miroslav and King, John S.}, year={2023}, month={Nov} }
 @article{mcnicol_fluet-chouinard_ouyang_knox_zhang_aalto_bansal_chang_chen_delwiche_et al._2023, title={Upscaling Wetland Methane Emissions From the FLUXNET-CH4 Eddy Covariance Network (UpCH4 v1.0): Model Development, Network Assessment, and Budget Comparison}, volume={4}, ISSN={["2576-604X"]}, DOI={10.1029/2023AV000956}, abstractNote={Abstract}, number={5}, journal={AGU ADVANCES}, author={McNicol, Gavin and Fluet-Chouinard, Etienne and Ouyang, Zutao and Knox, Sara and Zhang, Zhen and Aalto, Tuula and Bansal, Sheel and Chang, Kuang-Yu and Chen, Min and Delwiche, Kyle and et al.}, year={2023}, month={Oct} }
 @article{carvalho_aguilos_ile_howard_king_heitman_2023, title={Water use of short-rotation coppice American sycamore (Platanus occidentalis L.) for bioenergy during establishment on marginal land in the North Carolina Piedmont}, volume={276}, ISSN={0378-3774}, url={http://dx.doi.org/10.1016/j.agwat.2022.108071}, DOI={10.1016/j.agwat.2022.108071}, abstractNote={American sycamore (Platanus occidentalis L.) is a hardwood species that can be integrated into short-rotation coppice (SRC) production systems for bioenergy in the southeastern USA. Due to high growth rates and low input requirements, sycamore is regarded as a promising second-generation bioenergy woody crop suitable for degraded or marginal lands. However, little is known about sycamore water use for the conditions of North Carolina (NC), especially during the establishment year when trees are most sensitive to soil water deficits. We evaluated energy fluxes and actual crop evapotranspiration (ETc act) rates of sycamore SRC during the establishment year on marginal land in the Piedmont physiographic region of NC. Our overall goal was to better understand the factors controlling the evaporative demand of sycamore and its sensitivity to drought stress during establishment. Total ETc act was 482 mm, which was 95% of the total rainfall at the site. ETc act rates increased with precipitation and with tree development, reaching a maximum of 5.7 mm d−1. Although severe water stress was not observed during the study period, a moderate drought occurred from mid-August to mid-September, during which a 13-day drying cycle caused ETc act rates to decrease by 30%. The sycamore SRC transitioned from an “energy-limited” to a “water-limited” ETc act regime when water content in the upper 5 cm of soil was about 0.10 m3 m−3, indicating that the sycamore field relied on water available within the upper soil layers. Measurements suggested that trees may not yet have developed a root system sufficient to sustain transpiration during dry spells and that water use of the sycamore field was highly coupled to precipitation during the establishment year.}, journal={Agricultural Water Management}, publisher={Elsevier BV}, author={Carvalho, Henrique D.R. and Aguilos, Maricar M. and Ile, Omoyemeh J. and Howard, Adam M. and King, John S. and Heitman, Joshua L.}, year={2023}, month={Feb}, pages={108071} }
 @article{miao_noormets_gavazzi_mitra_domec_sun_mcnulty_king_2022, title={Beyond carbon flux partitioning: Carbon allocation and nonstructural carbon dynamics inferred from continuous fluxes}, ISSN={["1939-5582"]}, DOI={10.1002/eap.2655}, abstractNote={Abstract}, journal={ECOLOGICAL APPLICATIONS}, author={Miao, Guofang and Noormets, Asko and Gavazzi, Michael and Mitra, Bhaskar and Domec, Jean-Christophe and Sun, Ge and McNulty, Steve and King, John S.}, year={2022}, month={Jul} }
 @article{minick_aguilos_li_mitra_prajapati_king_2022, title={Effects of Spatial Variability and Drainage on Extracellular Enzyme Activity in Coastal Freshwater Forested Wetlands of Eastern North Carolina, USA}, volume={13}, ISSN={1999-4907}, url={http://dx.doi.org/10.3390/f13060861}, DOI={10.3390/f13060861}, abstractNote={Drainage of freshwater wetlands is common in coastal regions, although the effects on microbial extracellular enzyme activity (a key mediator of soil organic matter decomposition) in relation to spatial variability (microtopography and soil depth) are poorly understood. Soils were collected from organic (Oi, Oe, Oa) and mineral (A, AB, B) horizons from a natural and drained coastal forested wetland in North Carolina, USA. Activity of seven enzymes were measured: α-glucosidase (AG), β-glucosidase (BG), cellobiohydrolase (CBH), xylosidase (XYL), phenol oxidase (POX), peroxidase (PER) and N-acetyl glucosamide (NAG). Enzyme activity rates were normalized by soil weight, soil organic C (SOC), and microbial biomass C (MBC). Specific enzyme activity (per SOC or MBC) was more sensitive to drainage and soil depth compared to normalization by soil weight. In Oi and Oa horizons, specific enzyme activity (per MBC) (AG, BG, XYL, POX, PER) was higher in the natural compared to drained wetland but lower (AG, CBH, XYL, POX, PER, NAG) in the AB or B mineral soils. Results from this study indicate that organic soil horizons of natural freshwater wetlands contain a highly active microbial community driven by inputs of plant-derived C, while deeper soils of the drained wetland exhibit higher microbial metabolic activity, which likely plays a role in SOC storage of these systems.}, number={6}, journal={Forests}, publisher={MDPI AG}, author={Minick, Kevan J. and Aguilos, Maricar and Li, Xuefeng and Mitra, Bhaskar and Prajapati, Prajaya and King, John S.}, year={2022}, month={May}, pages={861} }
 @article{li_zheng_zhou_gavazzi_shan_mcnulty_king_2022, title={Effects of methodological difference on fine root production, mortality and decomposition estimates differ between functional types in a planted loblolly pine forest}, ISSN={["1573-5036"]}, DOI={10.1007/s11104-022-05737-2}, journal={PLANT AND SOIL}, author={Li, Xuefeng and Zheng, Xingbo and Zhou, Quanlai and Gavazzi, Michael and Shan, Yanlong and McNulty, Steven and King, John S.}, year={2022}, month={Oct} }
 @article{morkoc_aguilos_noormets_minick_ile_dickey_hardesty_kerrigan_heitman_king_2022, title={Environmental and Plant-Derived Controls on the Seasonality and Partitioning of Soil Respiration in an American Sycamore (Platanus occidentalis) Bioenergy Plantation Grown at Different Planting Densities}, volume={13}, ISSN={1999-4907}, url={http://dx.doi.org/10.3390/f13081286}, DOI={10.3390/f13081286}, abstractNote={Bioenergy is one of the most considered alternatives to fossil fuels. Short-rotation woody crops (SRWCs) as bioenergy sources are capable of alleviating energy constraints and sequestering atmospheric CO2. However, studies investigating soil carbon (C) dynamics at SWRC plantations are scarce. We studied American sycamore (Platanus occidentalis) as a model tree species for SRWC at different planting densities ((1) 0.5 × 2.0 m (10,000 trees·ha−1 or tph), (2) 1.0 × 2.0 m (5000 tph), and (3) 2.0 × 2.0 m (2500 tph)) to examine seasonal variation in total soil respiration (Rtotal), partitioned into heterotrophic (Rh) and autotrophic (Ra) respiration, and we evaluated climatic and biological controls on soil respiration. Rtotal and Rh exhibited larger seasonal variation than Ra (p < 0.05). During the nongrowing seasons, the average Rtotal was 0.60 ± 0.21 g·C·m−2·day−1 in winter and 1.41 ± 0.73 g·C·m−2·day−1 in fall. During the growing season, Rtotal was 2–7 times higher in spring (3.49 ± 1.44 g·C·m−2·day−1) and summer (4.01 ± 1.17 g·C·m−2·day−1) than winter. Average Rtotal was 2.30 ± 0.63 g·C·m−2·day−1 in 2500 tph, 2.43 ± 0.64 g·C·m−2·day−1 in 5000 tph, and 2.41 ± 0.75 g·C·m−2·day−1 in 10,000 tph treatments. Average Rh was 1.72 ± 0.40 g·C·m−2·day−1 in 2500 tph, 1.57 ± 0.39 g·C·m−2·day−1 in 5000 tph, and 1.93 ± 0.64 g·C·m−2·day−1 in 10,000 tph, whereas Ra had the lowest rates, with 0.59 ± 0.53 g·C·m−2·day−1 in 2500 tph, 0.86 ± 0.51 g·C·m−2·d−1 in 5000 tph, and 0.48 ± 0.34 g·C·m−2·day−1 in 10,000 tph treatments. Rh had a greater contribution to Rtotal (63%–80%) compared to Ra (20%–37%). Soil temperature was highly correlated to Rtotal (R2 = 0.92) and Rh (R2 = 0.77), while the correlation to Ra was weak (R2 = 0.21). Rtotal, Rh, and Ra significantly declined with soil water content extremes (e.g., <20% or >50%). Total root biomass in winter (469 ± 127 g·C·m−2) was smaller than in summer (616 ± 161 g·C·m−2), and the relationship of total root biomass to Rtotal, Rh, and Ra was only significant during the growing seasons (R2 = 0.12 to 0.50). The litterfall in 5000 tph (121 ± 16 g DW·m−2) did not differ (p > 0.05) from the 2500 tph (108 ± 16 g DW·m−2) or 10,000 tph (132 ± 16 g DW·m−2) treatments. In no circumstances were Rtotal, Rh, and Ra significantly correlated with litterfall amount across planting densities and seasons (p > 0.05). Overall, our results show that Rtotal in American sycamore SRWC is dominated by the heterotrophic component (Rh), is strongly correlated to soil environmental conditions, and can be minimized by planting at a certain tree density (5000 tph).}, number={8}, journal={Forests}, publisher={MDPI AG}, author={Morkoc, Suna and Aguilos, Maricar and Noormets, Asko and Minick, Kevan J. and Ile, Omoyemeh and Dickey, David A. and Hardesty, Deanna and Kerrigan, Maccoy and Heitman, Joshua and King, John}, year={2022}, month={Aug}, pages={1286} }
 @article{ile_mccormick_skrabacz_bhattacharya_aguilos_carvalho_idassi_baker_heitman_king_2022, title={Integrating Short Rotation Woody Crops into Conventional Agricultural Practices in the Southeastern United States: A Review}, volume={12}, ISSN={2073-445X}, url={http://dx.doi.org/10.3390/land12010010}, DOI={10.3390/land12010010}, abstractNote={One of the United Nations Sustainable Development Goal’s (SDGs) aims is to enhance access to clean energy. In addition, other SDGs are directly related to the restoration of degraded soils to improve on-farm productivity and land management. Integrating Short Rotation Woody Crops (SRWC) for bioenergy into conventional agriculture provides opportunities for sustainable domestic energy production, rural economic development/diversification, and restoration of soil health and biodiversity. Extensive research efforts have been carried out on the development of SRWC for bioenergy, biofuels, and bioproducts. Recently, broader objectives that include multiple ecosystem services, such as carbon sequestration, and land mine reclamation are being explored. Yet, limited research is available on the benefits of establishing SRWC on degraded agricultural lands in the southeastern U.S. thereby contributing to environmental goals. This paper presents a literature review to (1) synthesize the patterns and trends in SWRC bioenergy production; (2) highlight the benefits of integrating short rotation woody crops into row crop agriculture; and (3) identify emerging technologies for efficiently managing the integrated system, while identifying research gaps. Our findings show that integrating SRWC into agricultural systems can potentially improve the climate of agricultural landscapes and enhance regional and national carbon stocks in terrestrial systems.}, number={1}, journal={Land}, publisher={MDPI AG}, author={Ile, Omoyemeh J. and McCormick, Hanna and Skrabacz, Sheila and Bhattacharya, Shamik and Aguilos, Maricar and Carvalho, Henrique D. R. and Idassi, Joshua and Baker, Justin and Heitman, Joshua L. and King, John S.}, year={2022}, month={Dec}, pages={10} }
 @article{li_zheng_zhou_mcnulty_king_2022, title={Measurements of fine root decomposition rate: Method matters}, volume={164}, ISSN={["1879-3428"]}, DOI={10.1016/j.soilbio.2021.108482}, abstractNote={Fine root decomposition plays a major role in biogeochemical cycle in forests. Litterbags and intact cores are predominant methods for measuring fine root decomposition rate. However, their efficacies have not been critically reviewed. In this study, we identify six sources of error for both methods including use of unrepresentative substrates, changes in decomposer community composition, altered effects of living roots and mycorrhizal fungi, differences in experimental duration length and sampling regime, confounding of spatiotemporal resolution, and limited temporal resolution. We present an indirect method to quantify fine root decomposition rate by integrating soil core and minirhizotron measurements into a new equation. The indirect method requires measuring more fine root parameters but can generally overcome the weaknesses associated with litterbag and intact core methods. Directly measuring the decomposition rate inevitably disturbs interactions between roots, soil fauna and rhizosphere microbes, which could significantly undermine the credibility of the estimates. Indirect measurement based on fine root growth and death rates, biomass and necromass that can be assessed reliably should be the future choice.}, journal={SOIL BIOLOGY & BIOCHEMISTRY}, author={Li, Xuefeng and Zheng, Xingbo and Zhou, Quanlai and McNulty, Steven and King, John S.}, year={2022}, month={Jan} }
 @article{lin_noormets_king_marshall_akers_cucinella_fox_laviner_martin_mcnulty_et al._2022, title={Spatial variability in tree-ring carbon isotope discrimination in response to local drought across the entire loblolly pine natural range}, volume={42}, ISSN={["1758-4469"]}, DOI={10.1093/treephys/tpab097}, abstractNote={Abstract}, number={1}, journal={TREE PHYSIOLOGY}, author={Lin, Wen and Noormets, Asko and King, John S. and Marshall, John and Akers, Madison and Cucinella, Josh and Fox, Thomas R. and Laviner, Marshall A. and Martin, Timothy A. and Mcnulty, Steve and et al.}, year={2022}, month={Jan}, pages={44–58} }
 @article{aguilos_warr_irving_gregg_grady_peele_noormets_sun_liu_mcnulty_et al._2022, title={The Unabated Atmospheric Carbon Losses in a Drowning Wetland Forest of North Carolina: A Point of No Return?}, volume={13}, ISSN={1999-4907}, url={http://dx.doi.org/10.3390/f13081264}, DOI={10.3390/f13081264}, abstractNote={Coastal wetlands provide the unique biogeochemical functions of storing a large fraction of the terrestrial carbon (C) pool and being among the most productive ecosystems in the world. However, coastal wetlands face numerous natural and anthropogenic disturbances that threaten their ecological integrity and C storage potential. To monitor the C balance of a coastal forested wetland, we established an eddy covariance flux tower in a natural undrained bottomland hardwood forest in eastern North Carolina, USA. We examined the long-term trends (2009–2019) in gross primary productivity (GPP), ecosystem respiration (RE), and the net ecosystem C exchange (NEE) seasonally and inter-annually. We analyzed the response of C fluxes and balance to climatic and hydrologic forcings and examined the possible effects of rising sea levels on the inland groundwater dynamics. Our results show that in 2009, a higher annual GPP (1922 g C m−2 yr−1) was observed than annual RE (1554 g C m−2 yr−1), resulting in a net C sink (NEE = −368 g C m−2 yr−1). However, the annual C balance switched to a net C source in 2010 and onwards, varying from 87 g C m−2 yr−1 to 759 g C m−2 yr−1. The multiple effects of air temperature (Tair), net radiation (Rn), groundwater table (GWT) depth, and precipitation (p) explained 66%, 71%, and 29% of the variation in GPP, RE, and NEE, respectively (p < 0.0001). The lowering of GWT (−0.01 cm to −14.26 cm) enhanced GPP and RE by 35% and 28%, respectively. We also observed a significant positive correlation between mean sea level and GWT (R2 = 0.11), but not between GWT and p (R2 = 0.02). Cumulative fluxes from 2009 to 2019 showed continuing C losses owing to a higher rate of increase of RE than GPP. This study contributes to carbon balance accounting to improve ecosystem models, relating C dynamics to temporal trends in under-represented coastal forested wetlands.}, number={8}, journal={Forests}, publisher={MDPI AG}, author={Aguilos, Maricar and Warr, Ian and Irving, Madison and Gregg, Olivia and Grady, Stanton and Peele, Toby and Noormets, Asko and Sun, Ge and Liu, Ning and McNulty, Steve and et al.}, year={2022}, month={Aug}, pages={1264} }
 @article{lin_domec_ward_marshall_king_laviner_fox_west_sun_mcnulty_et al._2022, title={Using delta C-13 and delta O-18 to analyze loblolly pine (Pinus taeda L.) response to experimental drought and fertilization (vol 39, pg 1984, 2019)}, volume={42}, ISSN={["1758-4469"]}, DOI={10.1093/treephys/tpab162}, number={4}, journal={TREE PHYSIOLOGY}, author={Lin, Wen and Domec, Jean-Christophe and Ward, Eric J. and Marshall, John and King, John S. and Laviner, Marshall A. and Fox, Thomas R. and West, Jason B. and Sun, Ge and McNulty, Steve and et al.}, year={2022}, month={Apr}, pages={703–703} }
 @article{domec_king_carmichael_overby_wortemann_smith_miao_noormets_johnson_2021, title={Aquaporins, and not changes in root structure, provide new insights into physiological responses to drought, flooding, and salinity}, volume={72}, ISSN={["1460-2431"]}, DOI={10.1093/jxb/erab100}, abstractNote={Abstract}, number={12}, journal={JOURNAL OF EXPERIMENTAL BOTANY}, author={Domec, Jean-Christophe and King, John S. and Carmichael, Mary J. and Overby, Anna Treado and Wortemann, Remi and Smith, William K. and Miao, Guofang and Noormets, Asko and Johnson, Daniel M.}, year={2021}, month={May}, pages={4489–4501} }
 @article{aguilos_sun_noormets_domec_mcnulty_gavazzi_prajapati_minick_mitra_king_2021, title={Ecosystem Productivity and Evapotranspiration Are Tightly Coupled in Loblolly Pine (Pinus taeda L.) Plantations along the Coastal Plain of the Southeastern U.S.}, volume={12}, ISSN={1999-4907}, url={http://dx.doi.org/10.3390/f12081123}, DOI={10.3390/f12081123}, abstractNote={Forest water use efficiency (WUE), the ratio of gross primary productivity (GPP) to evapotranspiration (ET), is an important variable to understand the coupling between water and carbon cycles, and to assess resource use, ecosystem resilience, and commodity production. Here, we determined WUE for managed loblolly pine plantations over the course of a rotation on the coastal plain of North Carolina in the eastern U.S. We found that the forest annual GPP, ET, and WUE increased until age ten, which stabilized thereafter. WUE varied annually (2–44%), being higher at young plantation (YP, 3.12 ± 1.20 g C kg−1 H2O d−1) compared to a mature plantation (MP, 2.92 ± 0.45 g C kg−1 H2O d−1), with no distinct seasonal patterns. Stand age was strongly correlated with ET (R2 = 0.71) and GPP (R2 = 0.64). ET and GPP were tightly coupled (R2 = 0.86). Radiation and air temperature significantly affected GPP and ET (R2 = 0.71 − R2 = 0.82) at a monthly scale, but not WUE. Drought affected WUE (R2 = 0.35) more than ET (R2 = 0.25) or GPP (R2 = 0.07). A drought enhanced GPP in MP (19%) and YP (11%), but reduced ET 7% and 19% in MP and YP, respectively, resulting in a higher WUE (27–32%). Minor seasonal and interannual variation in forest WUE of MP (age > 10) suggested that forest functioning became stable as stands matured. We conclude that carbon and water cycles in loblolly pine plantations are tightly coupled, with different characteristics in different ages and hydrologic regimes. A stable WUE suggests that the pine ecosystem productivity can be readily predicted from ET and vice versa. The tradeoffs between water and carbon cycling should be recognized in forest management to achieve multiple ecosystem services (i.e., water supply and carbon sequestration).}, number={8}, journal={Forests}, publisher={MDPI AG}, author={Aguilos, Maricar and Sun, Ge and Noormets, Asko and Domec, Jean-Christophe and McNulty, Steven and Gavazzi, Michael and Prajapati, Prajaya and Minick, Kevan J. and Mitra, Bhaskar and King, John}, year={2021}, month={Aug}, pages={1123} }
 @article{aguilos_sun_noormets_domec_mcnulty_gavazzi_minick_mitra_prajapati_yang_et al._2021, title={Effects of land-use change and drought on decadal evapotranspiration and water balance of natural and managed forested wetlands along the southeastern US lower coastal plain}, volume={303}, ISSN={["1873-2240"]}, url={https://doi.org/10.1016/j.agrformet.2021.108381}, DOI={10.1016/j.agrformet.2021.108381}, abstractNote={Forested wetlands are important in regulating regional hydrology and climate. However, long-term studies on the hydrologic impacts of converting natural forested wetlands to pine plantations are rare for the southern US. From 2005-2018, we quantified water cycling in two post-harvest and newly-planted loblolly pine (Pinus taeda) plantations (YP2–7, 2–7 yrs old; YP2–8, 2–8 yrs old), a rotation-age loblolly pine plantation (MP, 15–28 yrs old), and a natural bottomland hardwood forest (BHF, > 100 yrs old) along the lower coastal plain of North Carolina. We quantified the differences in inter-annual and seasonal water balance and trends of evapotranspiration (ET) using eddy covariance over 37 site-years and assessed key climatic and biological drivers of ET. We found that the rotation-age plantation (MP) had higher annual ET (933 ± 63 mm) than the younger plantations (776 ± 74 mm for YP2–7 and 638 ± 190 mm for YP2–8), and the BHF (743 ± 172 mm), owing to differences in stand age, canopy cover, and micrometeorology. Chronosequence analysis of the pine sites showed that ET increased with stand age up to 10 years, then gradually stabilized for the remainder of the rotation of 28 – 30 years. YP2–8 was sensitive to water availability, decreasing ET by 30 – 43 % during the extreme 2007 – 2008 drought, but reductions in ET at MP were only 8 – 11 %. Comparing to BHF, ditching with management enhanced drainage at YP2–7 and YP2–8, while drainage was lower at the mature pine site. This study provides insight into land use-hydrology-climate interactions that have important implications for forested wetland management in a time of rapidly changing environmental conditions of the LCP of the southern US.}, journal={AGRICULTURAL AND FOREST METEOROLOGY}, author={Aguilos, Maricar and Sun, Ge and Noormets, Asko and Domec, Jean-Christophe and McNulty, Steve and Gavazzi, Michael and Minick, Kevan and Mitra, Bhaskar and Prajapati, Prajaya and Yang, Yun and et al.}, year={2021}, month={Jun} }
 @article{delwiche_knox_malhotra_fluet-chouinard_mcnicol_feron_ouyang_papale_trotta_canfora_et al._2021, title={FLUXNET-CH4: a global, multi-ecosystem dataset and analysis of methane seasonality from freshwater wetlands}, volume={13}, ISSN={["1866-3516"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85111811543&partnerID=MN8TOARS}, DOI={10.5194/essd-13-3607-2021}, abstractNote={Abstract. Methane (CH4) emissions from natural landscapes constitute
roughly half of global CH4 contributions to the atmosphere, yet large
uncertainties remain in the absolute magnitude and the seasonality of
emission quantities and drivers. Eddy covariance (EC) measurements of
CH4 flux are ideal for constraining ecosystem-scale CH4
emissions due to quasi-continuous and high-temporal-resolution CH4
flux measurements, coincident carbon dioxide, water, and energy flux
measurements, lack of ecosystem disturbance, and increased availability of
datasets over the last decade. Here, we (1) describe the newly published
dataset, FLUXNET-CH4 Version 1.0, the first open-source global dataset of
CH4 EC measurements (available at
https://fluxnet.org/data/fluxnet-ch4-community-product/, last access: 7 April 2021). FLUXNET-CH4
includes half-hourly and daily gap-filled and non-gap-filled aggregated
CH4 fluxes and meteorological data from 79 sites globally: 42
freshwater wetlands, 6 brackish and saline wetlands, 7 formerly drained
ecosystems, 7 rice paddy sites, 2 lakes, and 15 uplands. Then, we (2) evaluate FLUXNET-CH4 representativeness for freshwater wetland coverage
globally because the majority of sites in FLUXNET-CH4 Version 1.0 are
freshwater wetlands which are a substantial source of total atmospheric
CH4 emissions; and (3) we provide the first global estimates of the
seasonal variability and seasonality predictors of freshwater wetland
CH4 fluxes. Our representativeness analysis suggests that the
freshwater wetland sites in the dataset cover global wetland bioclimatic
attributes (encompassing energy, moisture, and vegetation-related
parameters) in arctic, boreal, and temperate regions but only sparsely
cover humid tropical regions. Seasonality metrics of wetland CH4
emissions vary considerably across latitudinal bands. In freshwater wetlands
(except those between 20∘ S to 20∘ N) the spring onset
of elevated CH4 emissions starts 3 d earlier, and the CH4
emission season lasts 4 d longer, for each degree Celsius increase in mean
annual air temperature. On average, the spring onset of increasing CH4
emissions lags behind soil warming by 1 month, with very few sites experiencing
increased CH4 emissions prior to the onset of soil warming. In
contrast, roughly half of these sites experience the spring onset of rising
CH4 emissions prior to the spring increase in gross primary
productivity (GPP). The timing of peak summer CH4 emissions does not
correlate with the timing for either peak summer temperature or peak GPP.
Our results provide seasonality parameters for CH4 modeling and
highlight seasonality metrics that cannot be predicted by temperature or GPP
(i.e., seasonality of CH4 peak). FLUXNET-CH4 is a powerful new resource
for diagnosing and understanding the role of terrestrial ecosystems and
climate drivers in the global CH4 cycle, and future additions of sites
in tropical ecosystems and site years of data collection will provide added
value to this database. All seasonality parameters are available at
https://doi.org/10.5281/zenodo.4672601 (Delwiche et al., 2021).
Additionally, raw FLUXNET-CH4 data used to extract seasonality parameters
can be downloaded from https://fluxnet.org/data/fluxnet-ch4-community-product/ (last access: 7 April 2021), and a complete
list of the 79 individual site data DOIs is provided in Table 2 of this paper.
                    }, number={7}, journal={EARTH SYSTEM SCIENCE DATA}, author={Delwiche, Kyle B. and Knox, Sara Helen and Malhotra, Avni and Fluet-Chouinard, Etienne and McNicol, Gavin and Feron, Sarah and Ouyang, Zutao and Papale, Dario and Trotta, Carlo and Canfora, Eleonora and et al.}, year={2021}, month={Jul}, pages={3607–3689} }
 @article{noormets_bracho_ward_seiler_strahm_lin_mcelligott_domec_gonzalez-benecke_jokela_et al._2021, title={Heterotrophic Respiration and the Divergence of Productivity and Carbon Sequestration}, volume={48}, ISSN={["1944-8007"]}, DOI={10.1029/2020GL092366}, abstractNote={Abstract}, number={7}, journal={GEOPHYSICAL RESEARCH LETTERS}, author={Noormets, Asko and Bracho, Rosvel and Ward, Eric and Seiler, John and Strahm, Brian and Lin, Wen and McElligott, Kristin and Domec, Jean-Christophe and Gonzalez-Benecke, Carlos and Jokela, Eric J. and et al.}, year={2021}, month={Apr} }
 @article{aguilos_brown_minick_fischer_ile_hardesty_kerrigan_noormets_king_2021, title={Millennial-Scale Carbon Storage in Natural Pine Forests of the North Carolina Lower Coastal Plain: Effects of Artificial Drainage in a Time of Rapid Sea Level Rise}, volume={10}, ISSN={2073-445X}, url={http://dx.doi.org/10.3390/land10121294}, DOI={10.3390/land10121294}, abstractNote={Coastal forested wetlands provide important ecosystem services along the southeastern region of the United States, but are threatened by anthropogenic and natural disturbances. Here, we examined the species composition, mortality, aboveground biomass, and carbon content of vegetation and soils in natural pine forests of the lower coastal plain in eastern North Carolina, USA. We compared a forest clearly in decline (termed “ghost forest”) adjacent to a roadside canal that had been installed as drainage for a road next to an adjacent forest subject to “natural” hydrology, unaltered by human modification (termed “healthy forest”). We also assessed how soil organic carbon (SOC) accumulation changed over time using 14C radiocarbon dating of wood sampled at different depths within the peat profile. Our results showed that the ghost forest had a higher tree density at 687 trees ha−1, and was dominated by swamp bays (Persea palustric), compared to the healthy forest, which had 265 trees ha−1 dominated by pond pine (Pinus serotina Michx). Overstory tree mortality of the ghost forest was nearly ten times greater than the healthy forest (p < 0.05), which actually contributed to higher total aboveground biomass (55.9 ± 12.6 Mg C ha−1 vs. 27.9 ± 8.7 Mg ha−1 in healthy forest), as the dead standing tree biomass (snags) added to that of an encroaching woody shrub layer during ecosystem transition. Therefore, the total aboveground C content of the ghost forest, 33.98 ± 14.8 Mg C ha−1, was higher than the healthy forest, 24.7 ± 5.2 Mg C ha−1 (p < 0.05). The total SOC stock down to a 2.3 m depth in the ghost forest was 824.1 ± 46.2 Mg C ha−1, while that of the healthy forest was 749.0 ± 170.5 Mg C ha−1 (p > 0.05). Carbon dating of organic sediments indicated that, as the sample age approaches modern times (surface layer year 2015), the organic soil accumulation rate (1.11 to 1.13 mm year−1) is unable to keep pace with the estimated rate of recent sea level rise (2.1 to 2.4 mm year−1), suggesting a causative relationship with the ecosystem transition occurring at the site. Increasing hydrologic stress over recent decades appears to have been a major driver of ecosystem transition, that is, ghost forest formation and woody shrub encroachment, as indicated by the far higher overstory tree mortality adjacent to the drainage ditch, which allows the inland propagation of hydrologic/salinity forcing due to SLR and extreme storms. Our study documents C accumulation in a coastal wetland over the past two millennia, which is now threatened due to the recent increase in the rate of SLR exceeding the natural peat accumulation rate, causing an ecosystem transition with unknown consequences for the stored C; however, much of it will eventually be returned to the atmosphere. More studies are needed to determine the causes and consequences of coastal ecosystem transition to inform the modeling of future coastal wetland responses to environmental change and the estimation of regional terrestrial C stocks and flux.}, number={12}, journal={Land}, publisher={MDPI AG}, author={Aguilos, Maricar and Brown, Charlton and Minick, Kevan and Fischer, Milan and Ile, Omoyemeh J. and Hardesty, Deanna and Kerrigan, Maccoy and Noormets, Asko and King, John}, year={2021}, month={Nov}, pages={1294} }
 @article{ile_aguilos_morkoc_minick_domec_king_2021, title={Productivity of low-input short-rotation coppice American sycamore ( Platanus occidentalis L.) grown at different planting densities as a bioenergy feedstock over two rotation cycles}, volume={146}, ISSN={["1873-2909"]}, url={https://doi.org/10.1016/j.biombioe.2021.105983}, DOI={10.1016/j.biombioe.2021.105983}, abstractNote={Short rotation coppice culture of woody crop species (SRWCs) has long been considered a sustainable method of producing biomass for bioenergy that does not compete with current food production practices. In this study, we grew American sycamore (Platanus occidentalis L.) for nine years corresponding to two rotation cycles (first rotation (FR) = 2010–2014, second rotation (SR) = 2015–2019). This was done at varying tree planting densities (1250, 2500, 5000, and 10,000 trees per hectare (tph)) on a degraded agricultural landscape under low-input (e.g. no fertilizer and low herbicide application) culture, in the Piedmont physiographic region of eastern North Carolina. Tree productivity was proportional to planting density, with the highest cumulative aboveground wood biomass in the 10,000 tph treatment, at 23.2 ± 0.9 Mg ha−1 and 39.1 ± 2.4 Mg ha−1 in the first and second rotations, respectively. These results demonstrate increasing productivity under a low-input SRWC management regime over the first two rotations. Biomass partitioning was strongly affected by planting density during FR, allocating less biomass to stems relative to other plant parts at low planting density (44–59% from 1250 to 10,000 tph, respectively). This effect disappeared during SR, however, with biomass partitioning to stems ranging from 74 to 79% across planting densities. Taken together, our results suggest that American sycamore has the potential to be effectively managed as a bioenergy feedstock with low input culture on marginal agriculture lands.}, journal={BIOMASS & BIOENERGY}, author={Ile, Omoyemeh J. and Aguilos, Maricar and Morkoc, Suna and Minick, Kevan and Domec, Jean-Christophe and King, John S.}, year={2021}, month={Mar} }
 @article{ile_aguilos_morkoc_heitman_king_2021, title={Root Biomass Distribution and Soil Physical Properties of Short-Rotation Coppice American Sycamore (Platanus occidentalis L.) Grown at Different Planting Densities}, volume={12}, ISSN={1999-4907}, url={http://dx.doi.org/10.3390/f12121806}, DOI={10.3390/f12121806}, abstractNote={Short rotation woody crops (SRWCs) provide sustainable, renewable biomass energy and offer potential ecosystem services, including increased carbon storage, reduced greenhouse gas emissions, and improved soil health. Establishing SRWCs on degraded lands has potential to enhance soil properties through root and organic matter turnover. A better understanding of SRWC planting density and its associated root turnover impacts on soil–air–water relations can improve management. In this study, we investigate the effects of planting density for a low-input American sycamore SRWC (no fertilization/irrigation) on soil physical properties for a degraded agricultural site in the North Carolina piedmont. The objectives were (1) to estimate the distributions of coarse and fine root biomass in three planting densities (10,000, 5000, and 2500 trees per hectare (tph)) and (2) to assess the effects of planting density on soil hydraulic properties and pore size distribution. Our results show that planting at 10,000 tph produced significantly higher amounts of fine root biomass than at lower planting densities (p < 0.01). In the 25,000 tph plots, there was significantly higher amounts of coarse root biomass than for higher planting densities (p < 0.05). The 10,000 tph plots had lower plant available water capacity but larger drainable porosity and saturated hydraulic conductivity compared with lower planting densities (<0.05). The 10,000 tph plots total porosity was more dominated by larger pore size fractions compared with the 5000 and 2500 tph. Generally, our findings show similar patterns of soil hydraulic properties and pore size distributions for lower planting densities. The results from 10,000 tph indicate a higher air-filled pore space at field capacity and more rapid drainage compared with lower planting densities. Both characteristics observed in the 10,000 tph are favorable for aeration and oxygen uptake, which are especially important at wet sites. Overall, the results suggest that improved soil health can be achieved from the establishment of American sycamore SRCs on marginal lands, thereby providing a green pathway to achieving environmental sustainability with woody renewable energy.}, number={12}, journal={Forests}, publisher={MDPI AG}, author={Ile, Omoyemeh Jennifer and Aguilos, Maricar and Morkoc, Suna and Heitman, Joshua and King, John S.}, year={2021}, month={Dec}, pages={1806} }
 @article{minick_mitra_li_fischer_aguilos_prajapati_noormets_king_2021, title={Wetland microtopography alters response of potential net CO2 and CH4 production to temperature and moisture: Evidence from a laboratory experiment}, volume={402}, ISSN={["1872-6259"]}, url={https://doi.org/10.1016/j.geoderma.2021.115367}, DOI={10.1016/j.geoderma.2021.115367}, abstractNote={Coastal wetlands store significant amounts of carbon (C) belowground, which may be altered through effects of rising temperature and changing hydrology on CO2 and CH4 fluxes and related microbial activities. Wetland microtopography (hummock-hollow) also plays a critical role in mediating plant growth, microbial activity, and thus cycling of C and nutrients and may interact with rising seas to influence coastal wetland C dynamics. Recent evidence suggests that CH4 production in oxygenated surface soils of freshwater wetlands may contribute substantially to global CH4 production, but comprehensive studies linking potential CH4 production to environmental and microbial variables in temperate freshwater forested wetlands are lacking. This study investigated effects of temperature, moisture, and microtopography on potential net CO2 and CH4 production and extracellular enzyme activity (β-glucosidase, xylosidase, phenol oxidase, and peroxidase) in peat soils collected from a freshwater forested wetland in coastal North Carolina, USA. Soils were retrieved from three microsites (hummock, hollow, and subsurface peat soils (approximately 20–40 cm below surface)) and incubated at two temperatures (27 °C and 32 °C) and soil water contents (65% and 100% water holding capacity (WHC)). Hummocks had the highest cumulative potential net CO2 (13.7 ± 0.90 mg CO2-C g soil−1) and CH4 (1.8 ± 0.42 mg CH4-C g soil−1) production and enzyme activity, followed by hollows (8.7 ± 0.91 mg CO2-C g soil−1 and 0.5 ± 0.12 mg CH4-C g soil−1) and then subsurface soils (5.7 ± 0.70 mg CO2-C g soil−1 and 0.04 ± 0.019 mg CH4-C g soil−1). Fully saturated soils had lower potential net CO2 production (50–80%) and substantially higher potential net CH4 production compared to non-saturated soils (those incubated at 65% WHC). Soils incubated at 32 °C increased potential net CO2 (24–34%) and CH4 (56–404%) production under both soil moisture levels compared to those incubated at 27 °C. The Q10 values for potential net CO2 and CH4 production ranged from 1.5 to 2.3 and 3.3–8.8, respectively, and did not differ between any microsites or soil water content. Enrichment of δ13CO2-C was found in saturated soils from all microsites (−24.4 to − 29.7 ‰) compared to non-saturated soils (−31.1 to − 32.4 ‰), while δ13CH4-C ranged from −62 to −55‰ in saturated soils. Together, the CO2 and CH4 δ13C data suggest that acetoclastic methanogenesis is an important pathway for CH4 production in these wetlands. A positive relationship (Adj. R2 = 0.40) between peroxidase activity and CH4 production was also found, indicating that peroxidase activity may be important in providing fermented C substrates to acetoclastic methanogenic communities and contribute to anaerobic C mineralization. These results suggest that changes in temperature and hydrology could stimulate CO2 and CH4 emissions from surface hummock soils, and to a lesser extent from hollow soils, and provide preliminary evidence that hummocks may be a spatially important and unrecognized hotspot for CH4 production.}, journal={GEODERMA}, author={Minick, Kevan J. and Mitra, Bhaskar and Li, Xuefeng and Fischer, Milan and Aguilos, Maricar and Prajapati, Prajaya and Noormets, Asko and King, John S.}, year={2021}, month={Nov} }
 @article{li_minick_li_williamson_gavazzi_mcnulty_king_2020, title={An improved method for quantifying total fine root decomposition in plantation forests combining measurements of soil coring and minirhizotrons with a mass balance model}, volume={40}, ISSN={["1758-4469"]}, DOI={10.1093/treephys/tpaa074}, abstractNote={Abstract}, number={10}, journal={TREE PHYSIOLOGY}, author={Li, Xuefeng and Minick, Kevan J. and Li, Tonghua and Williamson, James C. and Gavazzi, Michael and McNulty, Steven and King, John S.}, year={2020}, month={Oct}, pages={1466–1473} }
 @article{li_minick_luff_noormets_miao_mitra_domec_sun_mcnulty_king_2020, title={Effects of Microtopography on Absorptive and Transport Fine Root Biomass, Necromass, Production, Mortality and Decomposition in a Coastal Freshwater Forested Wetland, Southeastern USA}, volume={23}, ISSN={["1435-0629"]}, DOI={10.1007/s10021-019-00470-x}, abstractNote={Forested wetlands are an important carbon (C) sink. Fine roots (diameter < 2 mm) dominate belowground C cycling and can be functionally defined into absorptive roots (order 1–2) and transport roots (order ≥ 3). However, effects of microtopography on the function-based fine root dynamics in forested wetlands are poorly understood. We studied fine root biomass allocation and biomass, necromass, mass loss rate, production, mortality and decomposition of absorptive and transport roots in hummocks and hollows in a coastal plain freshwater forested wetland (FFW) in the southeastern USA using dynamic-flow method. Biomass ratios of first- to second-order roots and absorptive to transport roots and the biomass and necromass of absorptive and transport roots were significantly higher in top 0–10 cm organic peat layer than in 10–20 cm muck and mineral layer, and were significantly higher in hummocks than in hollows. The mass loss rate, production, mortality and decomposition were significantly higher in hummocks than in hollows. Absorptive roots did not have a lower mass loss rate than transport roots. Microtopography significantly affected the contributions of absorptive and transport roots to the total production, mortality and decomposition. Production, mortality and decomposition of absorptive roots were higher than those of transport roots in hummocks but lower than those of transport roots in hollows. Total (hummocks plus hollows) fine root production, mortality and decomposition were 455 ± 106 g m−2 y−1, 475 ± 79 g m−2 y−1 and 392 ± 60 g m−2 y−1, respectively. Greater mortality than decomposition resulted in net fine root C input to soil. The observed microtopographic controls on fine root dynamics have great implications for soil C cycling. As sea level rises, the relative area of hollows in coastal plain FFWs will increase, causing a decrease in fine root mass loss rate, biomass, production, mortality and decomposition and it is the balance of these processes that will determine future soil C storage and cycling.}, number={6}, journal={ECOSYSTEMS}, author={Li, Xuefeng and Minick, Kevan J. and Luff, Jordan and Noormets, Asko and Miao, Guofang and Mitra, Bhaskar and Domec, Jean-Christophe and Sun, Ge and McNulty, Steven and King, John S.}, year={2020}, month={Sep}, pages={1294–1308} }
 @article{aguilos_mitra_noormets_minick_prajapati_gavazzi_sun_mcnulty_li_domec_et al._2020, title={Long-term carbon flux and balance in managed and natural coastal forested wetlands of the Southeastern USA}, volume={288}, ISSN={["1873-2240"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85085132484&partnerID=MN8TOARS}, DOI={10.1016/j.agrformet.2020.108022}, abstractNote={Wetlands store large carbon (C) stocks and play important roles in biogeochemical C cycling. However, the effects of environmental and anthropogenic pressures on C dynamics in lower coastal plain forested wetlands in the southern U.S. are not well understood. We established four eddy flux stations in two post-harvest and newly-planted loblolly pine plantations (YP2–6, 2–6 yrs old; YP2–8, 2–8 yrs old), a rotation-aged loblolly pine plantations (MP, 15–27 yrs old), and a mixed bottomland hardwood forest (BHF, >100 yrs old) in the lower coastal plain of North Carolina, USA. We analyzed the gross primary productivity (GPP), ecosystem respiration (RE) and net ecosystem exchange (NEE) for age-related trends, interannual variability in response to climate forcing, and management-related disturbances from 2005 – 2017. For the first few years after being harvested, pine plantations were net C sources (NEE = 1133 and 897 g C m–2 yr–1 in YP2–6 and YP2–8, respectively). The MP was a strong C sink (–369 to –1131 g C m–2 yr–1) over the entire study period. In contrast, BHF was a C source (NEE = 87 g C m–2 yr–1 to 759 g C m–2 yr–1) in most years, although in the first year it did show a net C uptake (NEE = –368 g C m–2 yr–1). The source activity of BHF may have been related to increasing overstory tree mortality and diameter growth suppression. Decreases in relative extractable water in pine plantations enhanced GPP and RE. Pine plantations regained status as C sinks 5–8 years after harvest and recovered C equivalent to post-harvest losses at 8–14 years. Thus, coastal pine plantations have a net C uptake for only about half the 25-year rotation period, suggesting that they have decreased climate mitigation potential in comparison to protecting primary forests. However, primary forests in this area may be vulnerable to ecosystem transition, and subsequent C loss, due to the changing environmental conditions at the land-ocean interface.}, journal={AGRICULTURAL AND FOREST METEOROLOGY}, publisher={Elsevier BV}, author={Aguilos, Maricar and Mitra, Bhaskar and Noormets, Asko and Minick, Kevan and Prajapati, Prajaya and Gavazzi, Michael and Sun, Ge and McNulty, Steve and Li, Xuefeng and Domec, Jean-Christophe and et al.}, year={2020}, month={Jul} }
 @article{hannun_wolfe_kawa_hanisco_newman_alfieri_barrick_clark_digangi_diskin_et al._2020, title={Spatial heterogeneity in CO2, CH4, and energy fluxes: insights from airborne eddy covariance measurements over the Mid-Atlantic region}, volume={15}, ISSN={["1748-9326"]}, DOI={10.1088/1748-9326/ab7391}, abstractNote={Abstract}, number={3}, journal={ENVIRONMENTAL RESEARCH LETTERS}, author={Hannun, Reem A. and Wolfe, Glenn M. and Kawa, S. Randy and Hanisco, Thomas F. and Newman, Paul A. and Alfieri, Joseph G. and Barrick, John and Clark, Kenneth L. and DiGangi, Joshua P. and Diskin, Glenn S. and et al.}, year={2020}, month={Mar} }
 @article{mitra_minick_miao_domec_prajapati_mcnulty_sun_king_noormets_2020, title={Spectral evidence for substrate availability rather than environmental control of methane emissions from a coastal forested wetland}, volume={291}, ISSN={["1873-2240"]}, DOI={10.1016/j.agrformet.2020.108062}, abstractNote={Knowledge of the dynamics of methane (CH4) fluxes across coastal freshwater forested wetlands, such as those found in the southeastern US remains limited. In the current study, we look at the spectral properties of ecosystem net CH4 exchange (NEECH4) time series, and its cospectral behavior with key environmental conditions (temperature (Ts5), water table (WTD) and atmospheric pressure (Pa)) and physiological fluxes (photosynthesis (GPP), transpiration (LE), sap flux (Js)) using data from a natural bottomland hardwood swamp in eastern North Carolina. NEECH4 fluxes were measured over five years (2012 – 2016) that included both wet and dry years. During the growing season, strong cospectral peaks at diurnal scale were detected between CH4 efflux and GPP, LE and Js. This suggests that the well understood diurnal cycles in the latter processes may affect CH4 production through substrate availability (GPP) and transport (sap flow and LE). The causality between different time series was established by the magnitude and consistency of phase shifts. The causal effect of Ts5 and Pa were ruled out because despite cospectral peaks with CH4, their phase relationships were inconsistent. The effect of fluctuations in WTD on CH4 efflux at synoptic scale lacked clear indications of causality, possibly due to time lags and hysteresis. The stronger cospectral peak with ecosystem scale LE rather than Js suggested that the evaporative component of LE contributed equally with plant transpiration. Hence, we conclude that while the emission of dissolved gases through plants likely takes place, it may not contribute to higher CH4 emissions as has been proposed by aerenchymatous gas transport in sedge wetlands. These findings can inform future model development by (i) highlighting the coupling between vegetation processes and CH4 emissions, and (ii) identifying specific and non-overlapping timescales for different driving factors.}, journal={AGRICULTURAL AND FOREST METEOROLOGY}, author={Mitra, Bhaskar and Minick, Kevan and Miao, Guofang and Domec, Jean-Christophe and Prajapati, Prajaya and McNulty, Steve G. and Sun, Ge and King, John S. and Noormets, Asko}, year={2020}, month={Sep} }
 @article{feagin_forbrich_huff_barr_ruiz-plancarte_fuentes_najjar_vargas_vazquez-lule_windham-myers_et al._2020, title={Tidal Wetland Gross Primary Production Across the Continental United States, 2000-2019}, volume={34}, ISSN={["1944-9224"]}, DOI={10.1029/2019GB006349}, abstractNote={Abstract}, number={2}, journal={GLOBAL BIOGEOCHEMICAL CYCLES}, author={Feagin, R. A. and Forbrich, I. and Huff, T. P. and Barr, J. G. and Ruiz-Plancarte, J. and Fuentes, J. D. and Najjar, R. G. and Vargas, R. and Vazquez-Lule, A. and Windham-Myers, L. and et al.}, year={2020}, month={Feb} }
 @article{zhang_li_sun_king_2019, title={Coastal wetland resilience to climate variability: A hydrologic perspective}, volume={568}, ISSN={["1879-2707"]}, DOI={10.1016/j.jhydrol.2018.10.048}, abstractNote={Climate-induced disturbances are expected to increase in frequency and intensity and affect wetland ecology by altering its hydrology. Investigating how wetland hydrology responds to climate disturbances is an important first step to understand the ecological response of coastal wetlands to these disturbances. Wetland hydrologic resilience, the ability of wetland in absorbing disturbances and restoring to pre-disturbance conditions in hydrological function, is a critical measure of wetland hydrological response to climate disturbances. However, a practical methodology for quantifying wetland hydrologic resilience (HR) is still lacking. This study aimed to improve the approach for quantifying the hydrologic resilience of wetland ecosystems to climate variability and climate change. A set of quantitative metrics was developed including the variations of groundwater table, overland flow, and saltwater table. This approach was then applied to a coastal landscape that includes coastal-forested and herbaceous wetlands in North Carolina, USA. We investigated the threshold behaviors of groundwater table, overland flow, and saltwater table for a 20-year period (1995–2014) by applying a regional scale wetland hydrological model, Penn State Integrated Hydrological Model for wetland hydrology (PIHM-Wetland). We found that the multiscale variations of groundwater table under dry climatic conditions is a good indicator of wetland HR to drought. The variation of overland flow during rainfall events effectively quantified HR to wet periods. We also found that the variation of the water level of saltwater is an important metric of wetland HR to sea level rise. This study improves the methodology of quantifying wetland hydrologic resilience at a regional scale, representing an important first step towards understanding the wetland hydrological and ecological resilience to future intensified climate disturbances in coastal regions and beyond.}, journal={JOURNAL OF HYDROLOGY}, author={Zhang, Yu and Li, Wenhong and Sun, Ge and King, John S.}, year={2019}, month={Jan}, pages={275–284} }
 @article{mitra_miao_minick_mcnulty_sun_gavazzi_king_noormets_2019, title={Disentangling the Effects of Temperature, Moisture, and Substrate Availability on Soil CO2 Efflux}, volume={124}, ISSN={["2169-8961"]}, DOI={10.1029/2019JG005148}, abstractNote={Abstract}, number={7}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES}, author={Mitra, Bhaskar and Miao, Guofang and Minick, Kevan and McNulty, Steve G. and Sun, Ge and Gavazzi, Michael and King, John S. and Noormets, Asko}, year={2019}, month={Jul}, pages={2060–2075} }
 @article{minick_kelley_miao_li_noormets_mitra_king_2019, title={Microtopography Alters Hydrology, Phenol Oxidase Activity and Nutrient Availability in Organic Soils of a Coastal Freshwater Forested Wetland}, volume={39}, ISSN={["1943-6246"]}, DOI={10.1007/s13157-018-1107-5}, number={2}, journal={WETLANDS}, author={Minick, Kevan J. and Kelley, Alexia M. and Miao, Guofang and Li, Xuefeng and Noormets, Asko and Mitra, Bhaskar and King, John S.}, year={2019}, month={Apr}, pages={263–273} }
 @article{minick_mitra_noormets_king_2019, title={Saltwater reduces potential CO2 and CH4 production in peat soils from a coastal freshwater forested wetland}, volume={16}, ISSN={["1726-4189"]}, DOI={10.5194/bg-16-4671-2019}, abstractNote={Abstract. A major concern for coastal freshwater wetland function
and health is the effects of saltwater intrusion on greenhouse gas
production from peat soils. Coastal freshwater forested wetlands are likely
to experience increased hydroperiod with rising sea level, as well as
saltwater intrusion. These potential changes to wetland hydrology may also
alter forested wetland structure and lead to a transition from forest to
shrub/marsh wetland ecosystems. Loss of forested wetlands is already evident
by dying trees and dead standing trees (“ghost” forests) along the
Atlantic coast of the US, which will result in significant alterations to
plant carbon (C) inputs, particularly that of coarse woody debris, to soils.
We investigated the effects of salinity and wood C inputs on soils collected
from a coastal freshwater forested wetland in North Carolina, USA, and
incubated in the laboratory with either freshwater or saltwater (2.5 or 5.0 ppt) and with or without the additions of wood. Saltwater additions at 2.5 and 5.0 ppt reduced CO2 production by 41 % and 37 %, respectively,
compared to freshwater. Methane production was reduced by 98 % (wood-free
incubations) and by 75 %–87 % (wood-amended incubations) in saltwater
treatments compared to the freshwater plus wood treatment. Additions of wood
also resulted in lower CH4 production from the freshwater treatment and
higher CH4 production from saltwater treatments compared to wood-free
incubations. The δ13CH4-C isotopic signature suggested
that, in wood-free incubations, CH4 produced from the freshwater
treatment originated primarily from the acetoclastic pathway, while CH4
produced from the saltwater treatments originated primarily from the
hydrogenotrophic pathway. These results suggest that saltwater intrusion
into coastal freshwater forested wetlands will reduce CH4 production,
but long-term changes in C dynamics will likely depend on how changes in
wetland vegetation and microbial function influence C cycling in peat soils.
                    }, number={23}, journal={BIOGEOSCIENCES}, author={Minick, Kevan J. and Mitra, Bhaskar and Noormets, Asko and King, John S.}, year={2019}, month={Dec}, pages={4671–4686} }
 @article{minick_mitra_li_noormets_king_2019, title={Water Table Drawdown Alters Soil and Microbial Carbon Pool Size and Isotope Composition in Coastal Freshwater Forested Wetlands}, volume={2}, ISSN={["2624-893X"]}, DOI={10.3389/ffgc.2019.00007}, abstractNote={Loss of coastal wetlands is occurring at an increasingly rapid rate due to drainage of these wetlands for alternative land-uses, which also threatens carbon (C) storage in these C-rich ecosystems. Wetland drainage results in water table drawdown and increased peat aeration, which enhances decomposition of previously stabilized peat and changes stable C isotope profiles with soil depth. The effect of water table drawdown on the pool size and δ13C signature of plant C, soil organic C (SOC) and microbial biomass C (MBC) across a range of organic and mineral soils has not previously been reported in coastal freshwater forested wetlands. To this end, litter, roots, and soils were collected from organic and mineral soil horizons in two coastal freshwater forested wetlands in North Carolina with different hydrological regimes: 1) a natural bottomland hardwood forest (natural); and 2) a ditched and drained, intensively-managed wetland for loblolly pine silviculture (managed). We found that hydrology and soil horizon, and to a lesser degree micro-topography, was important in shaping observed differences in size and 13C signature of soil and microbial pools between the natural and managed wetland. The natural wetland had higher SOC and MBC concentrations in the litter, surface organic, and mineral horizons compared to the managed wetland. In the managed wetland, 13C of SOC was enriched across most of the soil profile (Oa and mineral soil horizons) compared to the natural wetland, suggesting enhanced decomposition and incorporation of microbially-derived inputs to soils. Root C concentration decreased with soil depth, while root 13C signature became enriched with soil depth. In the litter and Oe horizon of the natural wetland, MBC was higher and 13C of MBC and SOC was enriched in hummocks compared to hollows. The 13C of MBC and SOC tended to be enriched in upper soil horizons and depleted in lower soil horizons, particularly in the managed wetland. We conclude that drainage of these coastal wetlands has enhanced the breakdown of previously stabilized C and has the potential to alter regional C storage, feedbacks to climate warming, and ecosystem responses to changing environmental conditions.}, journal={FRONTIERS IN FORESTS AND GLOBAL CHANGE}, author={Minick, Kevan J. and Mitra, Bhaskar and Li, Xuefeng and Noormets, Asko and King, John S.}, year={2019}, month={Apr} }
 @article{li_king_2018, title={An improved method for measuring the production, mortality and decomposition of extramatrical mycelia of ectomycorrhizal fungi in forests}, volume={116}, ISSN={0038-0717}, url={http://dx.doi.org/10.1016/J.SOILBIO.2017.10.035}, DOI={10.1016/J.SOILBIO.2017.10.035}, abstractNote={Abstract The production and mortality of extramatrical mycelia (EMM) of ectomycorrhizal fungi are poorly quantified despite their importance in soil carbon cycling in forests. Ingrowth bag/core methods are the most widely used but can not accurately assess temporal changes in EMM production and mortality, resulting in great uncertainty in annual estimates. A modified method using two mathematical models (Biomarker and Algebraic models) is proposed to quantify EMM production, mortality and decomposition over differing time periods by integrating EMM decomposition dynamics with ingrowth core/bag data. In the Biomarker model, EMM biomass and EMM total mass (sum of necromass and biomass) are assumed to be known by using chemical biomarkers as proxies. In the Algebraic model, only the total mass is known and the biomass is calculated using an algebraic method. Model application in a loblolly pine plantation showed that mean monthly EMM production, mortality and decomposition estimates among three time periods ranged from 10.1 to 16.0 kg ha−1, 6.6–15.0 kg ha−1, and 1.4–6.1 kg ha−1, respectively, when using the Biomarker model, while these estimates ranged from 24.8 to 35.7 kg ha−1, 15.5–22.8 kg ha−1, and 5.7–9.8 kg ha−1, respectively, when using the Algebraic model, demonstrating the importance of assessing temporal changes. Model validation indicated that EMM estimates were more reliable for short-term compared to long-term incubation (184 vs. 322 days). Our method could improve EMM estimation by accurately assessing temporal changes in EMM production, mortality and decomposition in forests.}, journal={Soil Biology and Biochemistry}, publisher={Elsevier BV}, author={Li, Xuefeng and King, John S.}, year={2018}, month={Jan}, pages={360–368} }
 @article{liu_sun_mitra_noormets_gavazzi_domec_hallema_li_fang_king_et al._2018, title={Drought and thinning have limited impacts on evapotranspiration in a managed pine plantation on the southeastern United States coastal plain}, volume={262}, ISSN={0168-1923}, url={http://dx.doi.org/10.1016/j.agrformet.2018.06.025}, DOI={10.1016/j.agrformet.2018.06.025}, abstractNote={Managed and natural coastal plain forests in the humid southeastern United States exchange large amounts of water and energy with the atmosphere through the evapotranspiration (ET) process. ET plays an important role in controlling regional hydrology, climate, and ecosystem productivity. However, long-term studies on the impacts of forest management and climatic variability on forest ET are rare, and our understanding of both external and internal drivers on seasonal and interannual ET variability is incomplete. Using techniques centered on an eddy covariance method, the present study measured year-round ET flux and associated hydrometeorological variables in a drained loblolly pine (Pinus taeda L.) plantation on the lower coastal plain of North Carolina, U.S. We found that annual ET was relatively stable (1076 ± 104 mm) in comparison to precipitation (P) (1168 ± 216 mm) during the 10-year study period when the site experienced extreme climate (2007–2008) and forest thinning (2009). At the seasonal time scale, mean ET/P varied between 0.41 and 1.51, with a mean value of 1.12 ± 0.23 and 0.72 ± 0.16 for the growing and dormant seasons, respectively. The extreme drought during 2007–2008 (mean annual P, 854 mm) only resulted in a slight decrease (∼8%) in annual ET owing to the shallow groundwater common to the study area. Although changes in leaf area index and canopy structure were large after the stand was 50% thinned in the fall of 2009, mean annual ET was similar and averaged 1055 mm and 1104 mm before (2005, 2006 and 2009) and after (2010–2015) thinning, respectively. Data suggested that annual ET recovered within two years of the thinning as a result of rapid canopy closure and growth of understory. Further analysis indicated that available energy was the key driver of ET: approximately 69% and 61% of the monthly variations in ET were explained by net radiation during the dormant and growing seasons, respectively. Overall, we concluded that drought and forest thinning had limited impacts on seasonal and annual ET in this energy limited forest ecosystem with shallow groundwater. The results from this study help to better understand regional ecohydrological processes and projecting potential effects of forest management and extreme climate on water and carbon cycles.}, journal={Agricultural and Forest Meteorology}, publisher={Elsevier BV}, author={Liu, Xiaodong and Sun, Ge and Mitra, Bhaskar and Noormets, Asko and Gavazzi, Michael J. and Domec, Jean-Christophe and Hallema, Dennis W. and Li, Jiyue and Fang, Yuan and King, John S. and et al.}, year={2018}, month={Nov}, pages={14–23} }
 @article{tian_fischer_chescheir_youssef_cacho_king_2018, title={Microtopography-induced transient waterlogging affects switchgrass (Alamo) growth in the lower coastal plain of North Carolina, USA}, volume={10}, ISSN={["1757-1707"]}, DOI={10.1111/gcbb.12510}, abstractNote={Abstract}, number={8}, journal={GLOBAL CHANGE BIOLOGY BIOENERGY}, author={Tian, Shiying and Fischer, Milan and Chescheir, George M. and Youssef, Mohamed A. and Cacho, Julian F. and King, John S.}, year={2018}, month={Aug}, pages={577–591} }
 @article{zhang_li_sun_miao_noormets_emanuel_king_2018, title={Understanding coastal wetland hydrology with a new regional-scale, process-based hydrological model}, volume={32}, ISSN={["1099-1085"]}, url={http://dx.doi.org/10.1002/hyp.13247}, DOI={10.1002/hyp.13247}, abstractNote={Abstract}, number={20}, journal={HYDROLOGICAL PROCESSES}, author={Zhang, Yu and Li, Wenhong and Sun, Ge and Miao, Guofang and Noormets, Asko and Emanuel, Ryan and King, John S.}, year={2018}, month={Sep}, pages={3158–3173} }
 @article{fischer_zenone_trnka_orsag_montagnani_ward_tripathi_hlavinka_seufert_zalud_et al._2018, title={Water requirements of short rotation poplar coppice: Experimental and modelling analyses across Europe}, volume={250}, ISSN={["1873-2240"]}, DOI={10.1016/j.agrformet.2017.12.079}, abstractNote={Poplars are among the most widely used short rotation woody coppice (SRWC) species but due to their assumed high water use, concerns have been raised with respect to large-scale exploitation and potentially detrimental effects on water resources. Here we present a quantitative analysis of the water requirements of poplar SRWC using experimental data and a soil water balance modelling approach at three different sites across Europe. We used (i) eddy covariance (EC) measurements (2004–2006) at an irrigated SRWC grown on a previous rice paddy in northern Italy, (ii) Bowen ratio and energy balance (BREB) measurements (2008–2015) and EC (2011–2015) at a SRWC in rain-fed uplands in the Czech Republic, and (iii) EC measurements (2010–2013) at a SRWC on a previous agricultural land with a shallow water table in Belgium. Without any calibration against water balance component measurements, simulations by the newly developed soil water balance model R-4ET were compared with evapotranspiration (ET) measurements by EC and BREB with a resulting mean root mean square error (RMSE) of 0.75 mm day−1. In general, there was better agreement between EC and the model (RMSE = 0.66 mm day−1) when EC data were adjusted for lack of energy balance closure. A comparison of the simulated and measured soil water content yielded a mean RMSE of 0.03 m3 m−3. The mean annual crop coefficient, i.e. the ratio between actual and reference ET, was 0.82 (ranging from 0.65 to 0.95) while the monthly maxima reached 1.16. These values indicated that ET of poplar SRWC was significantly lower than ET of a well-watered grass cover at the annual time scale, but exceeded ET of the reference cover at shorter time scales during the growing season. We show that the model R-4ET is a simple, yet reliable tool for the assessment of water requirements of existing or planned SRWC. For very simple assessments on an annual basis, using a crop coefficient of 0.86 (adjusted to a sub-humid climate), representing an average value across the three sites in years with no evident drought stress, is supported by this analysis.}, journal={AGRICULTURAL AND FOREST METEOROLOGY}, author={Fischer, Milan and Zenone, Terenzio and Trnka, Miroslav and Orsag, Matej and Montagnani, Leonardo and Ward, Eric J. and Tripathi, Abhishek Mani and Hlavinka, Petr and Seufert, Gunther and Zalud, Zdenek and et al.}, year={2018}, month={Mar}, pages={343–360} }
 @article{fischer_kelley_ward_boone_ashley_domec_williamson_king_2017, title={A critical analysis of species selection and high vs. low-input silviculture on establishment success and early productivity of model short-rotation wood-energy cropping systems}, volume={98}, ISSN={["1873-2909"]}, DOI={10.1016/j.biombioe.2017.01.027}, abstractNote={Most research on bioenergy short rotation woody crops (SRWC) has been dedicated to the genera Populus and Salix. These species generally require relatively high-input culture, including intensive weed competition control, which increases costs and environmental externalities. Widespread native early successional species, characterized by high productivity and good coppicing ability, may be better adapted to local environmental stresses and therefore could offer alternative low-input bioenergy production systems. To test this concept, we established a three-year experiment comparing a widely-used hybrid poplar (Populus nigra × P. maximowiczii, clone ‘NM6’) to two native species, American sycamore (Platanus occidentalis L.) and tuliptree (Liriodendron tulipifera L.) grown under contrasting weed and pest control at a coastal plain site in eastern North Carolina, USA. Mean cumulative aboveground wood production was significantly greater in sycamore, with yields of 46.6 Mg ha−1 under high-inputs and 32.7 Mg ha−1 under low-input culture, which rivaled the high-input NM6 yield of 32.9 Mg ha−1. NM6 under low-input management provided noncompetitive yield of 6.2 Mg ha−1. Sycamore also showed superiority in survival, biomass increment, weed resistance, treatment convergence, and within-stand uniformity. All are important characteristics for a bioenergy feedstock crop species, leading to reliable establishment and efficient biomass production. Poor performance in all traits was found for tuliptree, with a maximum yield of 1.2 Mg ha−1, suggesting this native species is a poor choice for SRWC. We conclude that careful species selection beyond the conventionally used genera may enhance reliability and decrease negative environmental impacts of the bioenergy biomass production sector.}, journal={BIOMASS & BIOENERGY}, author={Fischer, M. and Kelley, A. M. and Ward, E. J. and Boone, J. D. and Ashley, E. M. and Domec, J. -C. and Williamson, J. C. and King, J. S.}, year={2017}, month={Mar}, pages={214–227} }
 @article{lin_noormets_king_sun_mcnulty_domec_2017, title={An extractive removal step optimized for a high-throughput alpha-cellulose extraction method for delta C-13 and delta O-18 stable isotope ratio analysis in conifer tree rings}, volume={37}, ISSN={["1758-4469"]}, DOI={10.1093/treephys/tpw084}, abstractNote={Stable isotope ratios (δ13C and δ18O) of tree-ring α-cellulose are important tools in paleoclimatology, ecology, plant physiology and genetics. The Multiple Sample Isolation System for Solids (MSISS) was a major advance in the tree-ring α-cellulose extraction methods, offering greater throughput and reduced labor input compared to traditional alternatives. However, the usability of the method for resinous conifer species may be limited by the need to remove extractives from some conifer species in a separate pretreatment step. Here we test the necessity of pretreatment for α-cellulose extraction in loblolly pine (Pinus taeda L.), and the efficiency of a modified acetone-based ambient-temperature step for the removal of extractives (i) in loblolly pine from five geographic locations representing its natural range in the southeastern USA, and (ii) on five other common coniferous species (black spruce (Picea mariana Mill.), Fraser fir (Abies fraseri (Pursh) Poir.), Douglas fir (Pseudotsuga menziesii (Mirb.) Franco), Norway spruce (Picea abies (L.) Karst) and ponderosa pine (Pinus ponderosa D.)) with contrasting extractive profiles. The differences of δ13C values between the new and traditional pretreatment methods were within the precision of the isotope ratio mass spectrometry method used (±0.2‰), and the differences between δ18O values were not statistically significant. Although some unanticipated results were observed in Fraser fir, the new ambient-temperature technique was deemed as effective as the more labor-consuming and toxic traditional pretreatment protocol. The proposed technique requires a separate acetone-inert multiport system similar to MSISS, and the execution of both pretreatment and main extraction steps allows for simultaneous treatment of up to several hundred microsamples from resinous softwood, while the need of additional labor input remains minimal.}, number={1}, journal={TREE PHYSIOLOGY}, author={Lin, Wen and Noormets, Asko and King, John S. and Sun, Ge and McNulty, Steve and Domec, Jean-Christophe}, year={2017}, month={Jan}, pages={142–150} }
 @article{miao_noormets_domec_fuentes_trettin_sun_mcnulty_king_2017, title={Hydrology and microtopography control carbon dynamics in wetlands: Implications in partitioning ecosystem respiration in a coastal plain forested wetland}, volume={247}, ISSN={["1873-2240"]}, DOI={10.1016/j.agrformet.2017.08.022}, abstractNote={Wetlands store a disproportionately large fraction of organic carbon relative to their areal coverage, and thus play an important role in global climate mitigation. As destabilization of these stores through land use or environmental change represents a significant climate feedback, it is important to understand the functional regulation of respiratory processes that catabolize them. In this study, we established an eddy covariance flux tower project in a coastal plain forested wetland in North Carolina, USA, and measured total ecosystem respiration (Re) over three years (2009–2011). We evaluated the magnitude and variability of three respiration components – belowground (Rs), coarse woody debris (RCWD), and aboveground plant (Ragp) respiration at the ecosystem scale, by accounting microtopographic variation for upscaling and constraining the mass balance with Re. Strong hydrologic control was detected for Rs and RCWD, whereas Ragp and Re were relatively insensitive to water table fluctuations. In a relatively dry year (2010), this forested wetland respired a total of about 2000 g CO2-C m-2 y-1 annually, 51% as Rs, 37% as Ragp, and 12% as RCWD. During non-flooded periods Rs contributed up to 57% of Re and during flooded periods Ragp contributed up to 69%. The contribution of Rs to Re increased by 2.4% for every cm of decrease in water level at intermediate water table level, and was nearly constant when flooded or when the water level more than 15 cm below ground. The contrasting sensitivity of different respiration components highlights the need for explicit consideration of this dynamic in ecosystem and Earth System Models.}, journal={AGRICULTURAL AND FOREST METEOROLOGY}, author={Miao, Guofang and Noormets, Asko and Domec, Jean-Christophe and Fuentes, Montserrat and Trettin, Carl C. and Sun, Ge and McNulty, Steve G. and King, John S.}, year={2017}, month={Dec}, pages={343–355} }
 @article{domec_ashley_fischer_noormets_boone_williamson_king_2017, title={Productivity, Biomass Partitioning, and Energy Yield of Low-Input Short-Rotation American Sycamore (Platanus occidentalis L.) Grown on Marginal Land: Effects of Planting Density and Simulated Drought}, volume={10}, ISSN={["1939-1242"]}, DOI={10.1007/s12155-017-9852-5}, number={3}, journal={BIOENERGY RESEARCH}, author={Domec, Jean-Christophe and Ashley, Elissa and Fischer, Milan and Noormets, Asko and Boone, Jameson and Williamson, James C. and King, John S.}, year={2017}, month={Sep}, pages={903–914} }
 @article{tian_cacho_youssef_chescheir_fischer_nettles_king_2017, title={Switchgrass growth and pine-switchgrass interactions in established intercropping systems}, volume={9}, ISSN={["1757-1707"]}, DOI={10.1111/gcbb.12381}, abstractNote={Abstract}, number={5}, journal={GLOBAL CHANGE BIOLOGY BIOENERGY}, author={Tian, Shiying and Cacho, Julian F. and Youssef, Mohamed A. and Chescheir, George M. and Fischer, Milan and Nettles, Jami E. and King, John S.}, year={2017}, month={May}, pages={845–857} }
 @article{ward_domec_king_sun_mcnulty_noormets_2017, title={TRACC: an open source software for processing sap flux data from thermal dissipation probes}, volume={31}, ISSN={["1432-2285"]}, DOI={10.1007/s00468-017-1556-0}, abstractNote={TRACC is an open-source software for standardizing the cleaning, conversion, and calibration of sap flux density data from thermal dissipation probes, which addresses issues of nighttime transpiration and water storage. Thermal dissipation probes (TDPs) have become a widely used method of monitoring plant water use in recent years. The use of TDPs requires calibration to a theoretical zero-flow value (∆T 0); usually based upon the assumption that at least some nighttime measurements represent zero-flow conditions. Fully automating the processing of data from TDPs is made exceedingly difficult due to errors arising from many sources. However, it is desirable to minimize variation arising from different researchers’ processing data, and thus, a common platform for processing data, including editing raw data and determination of ∆T 0, is useful and increases the transparency and replicability of TDP-based research. Here, we present the TDP data processing software TRACC (Thermal dissipation Review Assessment Cleaning and Conversion) to serve this purpose. TRACC is an open-source software written in the language R, using graphical presentation of data and on screen prompts with yes/no or simple numerical responses. It allows the user to select several important options, such as calibration coefficients and the exclusion of nights when vapor pressure deficit does not approach zero. Although it is designed for users with no coding experience, the outputs of TRACC could be easily incorporated into more complex models or software.}, number={5}, journal={TREES-STRUCTURE AND FUNCTION}, author={Ward, Eric J. and Domec, Jean-Christophe and King, John and Sun, Ge and McNulty, Steve and Noormets, Asko}, year={2017}, month={Oct}, pages={1737–1742} }
 @article{marchin_stout_davis_king_2017, title={Transgenically altered lignin biosynthesis affects photosynthesis and water relations of field-grown Populus trichocarpa}, volume={98}, ISSN={["1873-2909"]}, DOI={10.1016/j.biombioe.2017.01.013}, abstractNote={Concerns over energy security and environmental sustainability have stimulated interest in development of high-yield, low-lignin trees for bioenergy. Black cottonwood (Populus trichocarpa) has been targeted as a potential bioenergy species due to its high productivity, but it is unclear how transgenically altered lignin biosynthesis will affect plant function. We investigated the physiology of two transgenic P. trichocarpa genotypes grown in short rotation woody cropping systems at two sites in southeastern USA: (1) mesic mountain site and (2) warmer, drier Piedmont site. Our results suggest that lignin is fundamental for tree growth and survival in field environments. Lignin deficiency can decrease biochemical photosynthetic processes and interfere with the temperature-response of photosynthesis. Significantly, hydraulic conductivity of transgenic genotypes was 15–25% that of wildtype trees, resulting in decreased leaf-specific whole-plant hydraulic conductance. In the Piedmont, decreased hydraulic efficiency drastically reduced productivity of low-lignin genotypes by 50–70% relative to wildtype. Transgenic trees at the mountain site recovered stem lignin concentrations to levels observed in wildtype trees, but still had severely impaired hydraulic traits, highlighting the major consequences of genetic transformation on whole-plant function. Surprisingly, substantial loss of hydraulic conductivity had only minor effects on productivity at the mesic site and resulted in an alternative advantage for bioenergy systems – lower water consumption. In the hottest month (July), higher intrinsic water use efficiency resulted in total water savings of roughly 1 kg d−1 per transgenic tree without sacrificing productivity. Decreased hydraulic conductivity could therefore be a promising trait for selection of water-efficient genotypes in Populus.}, journal={BIOMASS & BIOENERGY}, author={Marchin, Renee M. and Stout, Anna T. and Davis, Aletta A. and King, John S.}, year={2017}, month={Mar}, pages={15–25} }
 @misc{matyssek_kozovits_wieser_king_rennenberg_2017, title={Woody-plant ecosystems under climate change and air pollution-response consistencies across zonobiomes?}, volume={37}, ISSN={["1758-4469"]}, DOI={10.1093/treephys/tpx009}, abstractNote={Forests store the largest terrestrial pools of carbon (C), helping to stabilize the global climate system, yet are threatened by climate change (CC) and associated air pollution (AP, highlighting ozone (O3) and nitrogen oxides (NOx)). We adopt the perspective that CC-AP drivers and physiological impacts are universal, resulting in consistent stress responses of forest ecosystems across zonobiomes. Evidence supporting this viewpoint is presented from the literature on ecosystem gross/net primary productivity and water cycling. Responses to CC-AP are compared across evergreen/deciduous foliage types, discussing implications of nutrition and resource turnover at tree and ecosystem scales. The availability of data is extremely uneven across zonobiomes, yet unifying patterns of ecosystem response are discernable. Ecosystem warming results in trade-offs between respiration and biomass production, affecting high elevation forests more than in the lowland tropics and low-elevation temperate zone. Resilience to drought is modulated by tree size and species richness. Elevated O3 tends to counteract stimulation by elevated carbon dioxide (CO2). Biotic stress and genomic structure ultimately determine ecosystem responsiveness. Aggrading early- rather than mature late-successional communities respond to CO2 enhancement, whereas O3 affects North American and Eurasian tree species consistently under free-air fumigation. Insect herbivory is exacerbated by CC-AP in biome-specific ways. Rhizosphere responses reflect similar stand-level nutritional dynamics across zonobiomes, but are modulated by differences in tree-soil nutrient cycling between deciduous and evergreen systems, and natural versus anthropogenic nitrogen (N) oversupply. The hypothesis of consistency of forest responses to interacting CC-AP is supported by currently available data, establishing the precedent for a global network of long-term coordinated research sites across zonobiomes to simultaneously advance both bottom-up (e.g., mechanistic) and top-down (systems-level) understanding. This global, synthetic approach is needed because high biological plasticity and physiographic variation across individual ecosystems currently limit development of predictive models of forest responses to CC-AP. Integrated research on C and nutrient cycling, O3-vegetation interactions and water relations must target mechanisms' ecosystem responsiveness. Worldwide case studies must be subject to biostatistical exploration to elucidate overarching response patterns and synthesize the resulting empirical data through advanced modelling, in order to provide regionally coherent, yet globally integrated information in support of internationally coordinated decision-making and policy development.}, number={6}, journal={TREE PHYSIOLOGY}, author={Matyssek, R. and Kozovits, A. R. and Wieser, G. and King, J. and Rennenberg, H.}, year={2017}, month={Jun}, pages={706–732} }
 @article{fang_sun_caldwell_mcnulty_noormets_domec_king_zhang_zhang_lin_et al._2016, title={Monthly land cover-specific evapotranspiration models derived from global eddy flux measurements and remote sensing data}, volume={9}, ISSN={["1936-0592"]}, DOI={10.1002/eco.1629}, abstractNote={Abstract}, number={2}, journal={ECOHYDROLOGY}, author={Fang, Yuan and Sun, Ge and Caldwell, Peter and McNulty, Steven G. and Noormets, Asko and Domec, Jean-Christophe and King, John and Zhang, Zhiqiang and Zhang, Xudong and Lin, Guanghui and et al.}, year={2016}, month={Mar}, pages={248–266} }
 @article{trnka_fischer_bartosova_orsag_kyncl_ceulemans_king_buntgen_2016, title={Potential and limitations of local tree ring records in estimating a priori the growth performance of short-rotation coppice plantations}, volume={92}, ISSN={["1873-2909"]}, DOI={10.1016/j.biombioe.2016.05.026}, abstractNote={As bioenergy plantations are a relatively new phenomenon, long-term experimental data on their productivity and tolerance to environmental stress that provides a robust framework for site selection and potential productivity assessment is still lacking. To address this need, we developed a method to correlate the productivity of bioenergy plantations with local climate using tree-ring chronologies. Tree-ring width from 37 Populus nigra (age > 115 y) and 368 poplar hybrid (Populus nigra × Populus maximowiczii) (9–12 y) individuals were collected and analyzed at demonstration sites in the Czech Republic. The growth of mature, naturally grown solitary native trees and young congeneric hybrids grown in high density (∼10,000 ha−1) showed statistically significant correlations (r = 0.71, p < 0.05). Further, we found significant (p < 0.05) and consistent growth responses to changes in key seasonal climatic parameters (e.g., mean air temperature, number of dry days or cumulative heat sum (degree-days) during the growing season) for both natives and their hybrids. The analysis of climate conditions and the tree-ring records revealed a gradual change of climatic conditions since the 1930s, positively affecting poplar growth and indicated that longer rather than shorter harvest cycles are preferable to ensure stable yields at our experimental site.}, journal={BIOMASS & BIOENERGY}, author={Trnka, Miroslav and Fischer, Milan and Bartosova, Lenka and Orsag, Matej and Kyncl, Tomas and Ceulemans, Reinhart and King, John and Buntgen, Ulf}, year={2016}, month={Sep}, pages={12–19} }
 @article{gahagan_giardina_king_binkley_pregitzer_burton_2015, title={Carbon fluxes, storage and harvest removals through 60 years of stand development in red pine plantations and mixed hardwood stands in Northern Michigan, USA}, volume={337}, ISSN={["1872-7042"]}, DOI={10.1016/j.foreco.2014.10.037}, abstractNote={The storage and flow of carbon (C) into and out of forests can differ under the influence of dominant tree species because of species-based variation in C production, decomposition, retention, and harvest-based export. Following abandonment of agricultural activities in the first half of the 20th century, many landscapes of the Great Lakes region (USA) were planted to red pine (Pinus resinosa) or naturally regenerated to northern hardwood species including sugar maple (Acer saccharum), red oak (Quercus rubra) and red maple (Acer rubrum). We located eight pairs of adjacent, similarly aged (∼60 yr) stands of planted red pine and naturally regenerated hardwood forests on previous agricultural fields. We found that the hardwood forests stored more C than pine stands (255 vs. 201 Mg C ha−1), with both storing substantially more than an adjacent area maintained as pasture (107 Mg C ha−1). The greater accumulation of C in the hardwood stands occurred mostly in living biomass. No significant differences for soil C (to 1 m depth) were found between forest types, despite significantly higher belowground inputs and aboveground litterfall in hardwood stands. Notably, both forest types had about 18% more soil C than the pasture, with O horizon C accounting for about one-third of the increase under trees. Forest type had no significant effect on estimated amount of exported C despite fairly large differences in projected end uses (solid wood products, land-fills, bioenergy). Using adjacent pasture as our baseline condition, we combined estimated on-site accumulation rates with estimates of exported C, and found that average total C sequestration rates were higher for hardwood (2.9 Mg C ha−1 yr−1) than red pine plots (2.3 Mg C ha−1 yr−1). The modeled potential contribution of exported C to these sequestration rate estimates did not differ between species, but the fate of modeled post-harvest off-site C may exert a large influence on sequestration rate estimates depending on actual displacement actions, including product longevity. These results show that tree species selection has the potential to impact C sequestration rates but effects vary by ecosystem component and could not be predicted from previous species effects studies.}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Gahagan, Adam and Giardina, Christian P. and King, John S. and Binkley, Dan and Pregitzer, Kurt S. and Burton, Andrew J.}, year={2015}, month={Feb}, pages={88–97} }
 @article{domec_king_ward_oishi_palmroth_radecki_bell_miao_gavazzi_johnson_et al._2015, title={Conversion of natural forests to managed forest plantations decreases tree resistance to prolonged droughts}, volume={355}, ISSN={["1872-7042"]}, DOI={10.1016/j.foreco.2015.04.012}, abstractNote={Throughout the southern US, past forest management practices have replaced large areas of native forests with loblolly pine plantations and have resulted in changes in forest response to extreme weather conditions. However, uncertainty remains about the response of planted versus natural species to drought across the geographical range of these forests. Taking advantage of a cluster of unmanaged stands (85–130 year-old hardwoods) and managed plantations (17–20 year-old loblolly pine) in coastal and Piedmont areas of North Carolina, tree water use, cavitation resistance, whole-tree hydraulic (Ktree) and stomatal (Gs) conductances were measured in four sites covering representative forests growing in the region. We also used a hydraulic model to predict the resilience of those sites to extreme soil drying. Our objectives were to determine: (1) if Ktree and stomatal regulation in response to atmospheric and soil droughts differ between species and sites; (2) how ecosystem type, through tree water use, resistance to cavitation and rooting profiles, affects the water uptake limit that can be reached under drought; and (3) the influence of stand species composition on critical transpiration that sets a functional water uptake limit under drought conditions. The results show that across sites, water stress affected the coordination between Ktree and Gs. As soil water content dropped below 20% relative extractable water, Ktree declined faster and thus explained the decrease in Gs and in its sensitivity to vapor pressure deficit. Compared to branches, the capability of roots to resist high xylem tension has a great impact on tree-level water use and ultimately had important implications for pine plantations resistance to future summer droughts. Model simulations revealed that the decline in Ktree due to xylem cavitation aggravated the effects of soil drying on tree transpiration. The critical transpiration rate (Ecrit), which corresponds to the maximum rate at which transpiration begins to level off to prevent irreversible hydraulic failure, was higher in managed forest plantations than in their unmanaged counterparts. However, even with this higher Ecrit, the pine plantations operated very close to their critical leaf water potentials (i.e. to their permissible water potentials without total hydraulic failure), suggesting that intensively managed plantations are more drought-sensitive and can withstand less severe drought than natural forests.}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Domec, Jean-Christophe and King, John S. and Ward, Eric and Oishi, A. Christopher and Palmroth, Sari and Radecki, Andrew and Bell, Dave M. and Miao, Guofang and Gavazzi, Michael and Johnson, Daniel M. and et al.}, year={2015}, month={Nov}, pages={58–71} }
 @misc{noormets_epron_domec_mcnulty_fox_sun_king_2015, title={Effects of forest management on productivity and carbon sequestration: A review and hypothesis}, volume={355}, ISSN={["1872-7042"]}, DOI={10.1016/j.foreco.2015.05.019}, abstractNote={With an increasing fraction of the world’s forests being intensively managed for meeting humanity’s need for wood, fiber and ecosystem services, quantitative understanding of the functional changes in these ecosystems in comparison with natural forests is needed. In particular, the role of managed forests as long-term carbon (C) sinks and for mitigating climate change require a detailed assessment of their carbon cycle on different temporal scales. In the current review we assess available data on the structure and function of the world’s forests, explore the main differences in the C exchange between managed and unmanaged stands, and explore potential physiological mechanisms behind both observed and expected changes. Two global databases that include classification for management indicate that managed forests are about 50 years younger, include 25% more coniferous stands, and have about 50% lower C stocks than unmanaged forests. The gross primary productivity (GPP) and total net primary productivity (NPP) are the similar, but relatively more of the assimilated carbon is allocated to aboveground pools in managed than in unmanaged forests, whereas allocation to fine roots and rhizosymbionts is lower. This shift in allocation patterns is promoted by increasing plant size, and by increased nutrient availability. Long-term carbon sequestration potential in soils is assessed through the ratio of heterotrophic respiration to total detritus production, which indicates that (i) the forest soils may be losing more carbon on an annual basis than they regain in detritus, and (ii) the deficit appears to be greater in managed forests. While climate change and management factors (esp. fertilization) both contribute to greater carbon accumulation potential in the soil, the harvest-related increase in decomposition affects the C budget over the entire harvest cycle. Although the findings do not preclude the use of forests for climate mitigation, maximizing merchantable productivity may have significant carbon costs for the soil pool. We conclude that optimal management strategies for maximizing multiple benefits from ecosystem services require better understanding of the dynamics of belowground allocation, carbohydrate availability, heterotrophic respiration, and carbon stabilization in the soil.}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Noormets, A. and Epron, D. and Domec, J. C. and McNulty, S. G. and Fox, T. and Sun, G. and King, J. S.}, year={2015}, month={Nov}, pages={124–140} }
 @article{ward_domec_laviner_fox_sun_mcnulty_king_noormets_2015, title={Fertilization intensifies drought stress: Water use and stomatal conductance of Pinus taeda in a midrotation fertilization and throughfall reduction experiment}, volume={355}, ISSN={["1872-7042"]}, DOI={10.1016/j.foreco.2015.04.009}, abstractNote={While mid-rotation fertilization increases productivity in many southern pine forests, it remains unclear what impact such management may have on stand water use. We examined the impact of nutrient and water availability on stem volume, leaf area, transpiration per unit ground area (EC) and canopy conductance per unit leaf area (GS) of a pine plantation during its 8th and 9th growing seasons. Treatments consisted of a factorial combination of throughfall reduction (30% reduction in throughfall versus ambient) and fertilization (a complete suite of essential nutrients) beginning in April 2012. Overall, our results indicate that despite unusually high rainfall in the study period and a lack of leaf area index (LAI) response, both EC and GS decreased in response to fertilization and throughfall reduction. Fertilization increased stem volume increment 21% in 2013. Treatment differences were greatest in the growing season of 2013, when EC was on average 19%, 13% and 29% lower in the throughfall reduction (D), fertilization (F) and combined treatment (FD) than the control (C), respectively. The responses of GS to volumetric soil water content (VWC) indicate that lower EC in F was associated with a decrease relative to C in GS at high VWC. Decreases of GS in D relative to C were associated with lower VWC, but little change in the response of GS to VWC. Decreases observed in FD resulted from a combination of these two factors. The pattern of GS responses in the different treatments suggests that structural or physiological changes underlie this fertilization response, possibly in fine root area or hydraulic conductivity. In the short term, this led to large increases in the water use efficiency of stem production, which could suggest greater resiliency to minor water stress. However, impacts on long-term sensitivity to drought remain a concern, as the EC reduction triggered by the fertilization treatment was of comparable magnitude to the 30% throughfall exclusion treatment and the greatest reductions were found in the combined treatment.}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Ward, Eric J. and Domec, Jean-Christophe and Laviner, Marshall A. and Fox, Thomas R. and Sun, Ge and McNulty, Steve and King, John and Noormets, Asko}, year={2015}, month={Nov}, pages={72–82} }
 @article{tian_youssef_sun_chescheir_noormets_amatya_skaggs_king_mcnulty_gavazzi_et al._2015, title={Testing DRAINMOD-FOREST for predicting evapotranspiration in a mid-rotation pine plantation}, volume={355}, ISSN={["1872-7042"]}, DOI={10.1016/j.foreco.2015.03.028}, abstractNote={Evapotranspiration (ET) is a key component of the hydrologic cycle in terrestrial ecosystems and accurate description of ET processes is essential for developing reliable ecohydrological models. This study investigated the accuracy of ET prediction by the DRAINMOD-FOREST after its calibration/validation for predicting commonly measured hydrological variables. The model was tested by conducting an eight year simulation of drainage and shallow groundwater dynamics in a managed mid-rotation loblolly pine (Pinus taeda L.) plantation located in the coastal plain of North Carolina, USA. Modeled daily ET rates were compared to those measured in the field using the eddy covariance technique. In addition, the wavelet transform and coherence analysis were used to compare ET predictions and measurements on the time–frequency domain. Results showed that DRAINMOD-FOREST accurately predicted annual and monthly ET after a successful calibration and validation using measured drainage rates and water table depth. The model under predicted ET on an annual basis by 2%, while the Nash–Sutcliffe coefficient of model predictions on a monthly basis was 0.78. Results from wavelet transform and coherence analysis demonstrated that the model reasonably captured the high power spectra of ET at an annual scale with significantly high model-data coherency. These results suggested that the calibrated DRAINMOD-FOREST collectively captured key factors and mechanisms controlling ET dynamics in the drained pine plantation. However, the global power spectrum revealed that the model over predicted the power spectrum of ET at an annual scale, suggesting the model may have under predicted canopy conductance during non-growing seasons. In addition, this study also suggested that DRAINMOD-FOREST did not properly capture the seasonal dynamics of ET under extreme drought conditions with deeper water table depths. These results suggested further refinement to parameters, particularly vegetation related, and structures of DRAINMOD-FOREST to achieve better agreement between ET predictions and measurements in the time–frequency domain.}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Tian, Shiying and Youssef, Mohamed A. and Sun, Ge and Chescheir, George M. and Noormets, Asko and Amatya, Devendra M. and Skaggs, R. Wayne and King, John S. and McNulty, Steve and Gavazzi, Michael and et al.}, year={2015}, month={Nov}, pages={37–47} }
 @article{albaugh_albaugh_heiderman_leggett_stape_king_katherine p. o'neill_king_2014, title={Evaluating changes in switchgrass physiology, biomass, and light-use efficiency under artificial shade to estimate yields if intercropped with Pinus taeda L.}, volume={88}, ISSN={["1572-9680"]}, DOI={10.1007/s10457-014-9708-3}, number={3}, journal={AGROFORESTRY SYSTEMS}, author={Albaugh, Janine M. and Albaugh, Timothy J. and Heiderman, Ryan R. and Leggett, Zakiya and Stape, Jose L. and King, Kyle and Katherine P. O'Neill and King, John S.}, year={2014}, month={Jun}, pages={489–503} }
 @article{albaugh_domec_maier_sucre_leggett_king_2014, title={Gas exchange and stand-level estimates of water use and gross primary productivity in an experimental pine and switchgrass intercrop forestry system on the Lower Coastal Plain of North Carolina, USA}, volume={192}, ISSN={["1873-2240"]}, DOI={10.1016/j.agrformet.2014.02.013}, abstractNote={Despite growing interest in using switchgrass (Panicum virgatum L.) as a biofuel, there are limited data on the physiology of this species and its effect on stand water use and carbon (C) assimilation when grown as a forest intercrop for bioenergy. Therefore, we quantified gas exchange rates of switchgrass within intercropped plots and in pure switchgrass plots during its second growing season in an intensively managed loblolly pine (Pinus taeda L.) plantation in North Carolina. Switchgrass physiology was characterized over the growing season from June to October 2010 in terms of photosynthesis (μmol m−2 s−1), stomatal conductance (mmol m−2 s−1), and assimilation responses to photosynthetic photon flux density and intercellular carbon dioxide concentration (CO2). We then used a process-based model of the soil–plant–atmosphere continuum to scale leaf-level gas exchange data to provide estimates of pine and switchgrass stand-level water use (mm) and carbon exchange (g C m−2) over a three-year period. Peak switchgrass photosynthesis (32.7 ± 0.9 μmol m−2 s−1) and stomatal conductance (252 ± 12 mmol m−2 s−1) rates were measured in July, with minimum values (18.7 ± 1.4 μmol m−2 s−1 and 104 ± 6 mmol m−2 s−1, respectively) recorded at the end of the growing season (October). Switchgrass gas exchange and parameter estimates from the light- and CO2 response curves did not vary between treatments. However, gas exchange values differed significantly between measurement dates. Model predictions of stand-level transpiration ranged from 287 to 431 mm year−1 for pine and from 245 to 296 mm year−1 for switchgrass. Annual C exchange for loblolly pine ranged from 1165 to 1903 g m−2 compared to 1386 to 1594 g m−2 for switchgrass. At this stage of stand development, no effect of intercropping was evident and there was no effect of distance from the nearest pine row on any switchgrass gas exchange variable measured. However, we anticipate that as this intercropped system develops over time, competition for resources such as light, water or nitrogen may change, with the potential to impact switchgrass physiology and biomass production.}, journal={AGRICULTURAL AND FOREST METEOROLOGY}, author={Albaugh, Janine M. and Domec, Jean-Christophe and Maier, Chris A. and Sucre, Eric B. and Leggett, Zakiya H. and King, John S.}, year={2014}, month={Jul}, pages={27–40} }
 @article{stout_davis_domec_yang_shi_king_2014, title={Growth under field conditions affects lignin content and productivity in transgenic Populus trichocarpa with altered lignin biosynthesis}, volume={68}, ISSN={["1873-2909"]}, DOI={10.1016/j.biombioe.2014.06.008}, abstractNote={This study evaluated the potential of transgenic Populus trichocarpa with antisense 4CL for reduced total lignin and sense Cald5H for increased S/G ratio in a short rotation woody cropping (SRWC) system for bioethanol production in the Southeast USA. Trees produced from tissue-culture were planted in the Coastal Plain, Piedmont, and Mountain regions of North Carolina, USA. Trees were observed for growth differences and biomass recorded for two coppices. Insoluble lignin and S/G ratio were determined by molecular beam mass spectroscopy after the second coppice. Survival, growth form, and biomass were very consistent within construct lines. Higher total lignin content and S/G ratio were positively correlated with total aboveground biomass. The low-lignin phenotype was not completely maintained in the field, with total lignin content increasing on average more than 30.0% at all sites by the second coppice The capacity to upregulate lignin in the event of environmental stress may have helped some low-lignin lines to survive. More research focused on promising construct lines in appropriate environmental conditions is needed to clarify if a significant reduction in lignin can be achieved on a plantation scale, and whether that reduction will translate into increased efficiency of enzymatic hydrolysis.}, journal={BIOMASS & BIOENERGY}, author={Stout, Anna T. and Davis, Aletta A. and Domec, Jean-Christophe and Yang, Chenmin and Shi, Rui and King, John S.}, year={2014}, month={Sep}, pages={228–239} }
 @article{kelley_king_2014, title={Pest pressure, hurricanes, and genotype interact to strongly impact stem form in young loblolly pine (Pinus taeda L.) along the coastal plain of North Carolina}, volume={28}, ISSN={["1432-2285"]}, DOI={10.1007/s00468-014-1039-5}, number={5}, journal={TREES-STRUCTURE AND FUNCTION}, author={Kelley, Alexia M. and King, John S.}, year={2014}, month={Oct}, pages={1343–1353} }
 @article{king_kelley_rees_2014, title={Systemic Control of Nantucket Pine Tip Moth (Rhyacionia frustrana Scudder in Comstock, 1880) Enhances Seedling Vigor, Plantation Establishment, and Early Stand-Level Productivity in Pinus taeda L.}, volume={60}, ISSN={["1938-3738"]}, DOI={10.5849/forsci.12-081}, abstractNote={Establishment is a vulnerable and expensive stage of stand development in intensively managed pine plantations. We evaluated the capacity of establishing loblolly pine (Pinus taeda L.) plantations to increase productivity by systemic control of Nantucket pine tip moth (Rhyacionia frustrana Scudder in Comstock, 1880). In January 2009, four genotypes of improved genetics loblolly pine were planted in whole-plot treatments of herbaceous competition control at an upper coastal plain (UCP) site and phosphorus fertilization at a lower coastal plain (LCP) site, and split-plot treatments of tip moth control. Trees were monitored for tip moth infestation levels, vigor, survival, and stand-level biomass production for 2 years. During this time, tip moth infestation levels were very high at both sites, averaging 69% at UCP and 70% at LCP. However, levels averaged only 8% at UCP and 39% at LCP in treatments that included applications of systemic insecticides at planting. At LCP, biomass production averaged 2,159 kg ha 1 after 2 years. Protection from tip moth increased LCP biomass by 11% averaged across genotypes and 20 –30% for the most responsive genotypes. At UCP, 2-year pine biomass production was much lower at 114.5 kg ha 1 and was increased 150% by protection from tip moth. At UCP, there was a strong effect of genetics whereby one genotype experienced very high mortality (mean of 30%) attributed to meteorological conditions of the establishment year; however, this was greatly decreased (17%) by protection from the interacting stress of tip moth damage. We conclude that systemic control of tip moth using imidacloprid soil tablets has the potential to greatly enhance pine plantation establishment success and early productivity in areas of heavy pest pressure, which may compound through stand development.}, number={1}, journal={FOREST SCIENCE}, author={King, John S. and Kelley, Alexia M. and Rees, Richard}, year={2014}, month={Feb}, pages={97–108} }
 @article{berhongaray_king_janssens_ceulemans_2013, title={An optimized fine root sampling methodology balancing accuracy and time investment}, volume={366}, ISSN={["0032-079X"]}, DOI={10.1007/s11104-012-1438-6}, number={1-2}, journal={PLANT AND SOIL}, author={Berhongaray, G. and King, J. S. and Janssens, I. A. and Ceulemans, R.}, year={2013}, month={May}, pages={351–361} }
 @article{djomo_el kasmioui_de groote_broeckx_verlinden_berhongaray_fichot_zona_dillen_king_et al._2013, title={Energy and climate benefits of bioelectricity from low-input short rotation woody crops on agricultural land over a two-year rotation}, volume={111}, ISSN={["1872-9118"]}, DOI={10.1016/j.apenergy.2013.05.017}, abstractNote={Short-rotation woody crops (SRWCs) are a promising means to enhance the EU renewable energy sources while mitigating greenhouse gas (GHG) emissions. However, there are concerns that the GHG mitigation potential of bioelectricity may be nullified due to GHG emissions from direct land use changes (dLUCs). In order to evaluate quantitatively the GHG mitigation potential of bioelectricity from SRWC we managed an operational SRWC plantation (18.4 ha) for bioelectricity production on a former agricultural land without supplemental irrigation or fertilization. We traced back to the primary energy level all farm labor, materials, and fossil fuel inputs to the bioelectricity production. We also sampled soil carbon and monitored fluxes of GHGs between the SRWC plantation and the atmosphere. We found that bioelectricity from SRWCs was energy efficient and yielded 200–227% more energy than required to produce it over a two-year rotation. The associated land requirement was 0.9 m2kWhe-1 for the gasification and 1.1 m2kWhe-1 for the combustion technology. Converting agricultural land into the SRWC plantation released 2.8 ± 0.2 t CO2e ha−1, which represented ∼89% of the total GHG emissions (256–272 g CO2e kWhe-1) of bioelectricity production. Despite its high share of the total GHG emissions, dLUC did not negate the GHG benefits of bioelectricity. Indeed, the GHG savings of bioelectricity relative to the EU non-renewable grid mix power ranged between 52% and 54%. SRWC on agricultural lands with low soil organic carbon stocks are encouraging prospects for sustainable production of renewable energy with significant climate benefits.}, journal={APPLIED ENERGY}, author={Djomo, S. Njakou and El Kasmioui, O. and De Groote, T. and Broeckx, L. S. and Verlinden, M. S. and Berhongaray, G. and Fichot, R. and Zona, D. and Dillen, S. Y. and King, J. S. and et al.}, year={2013}, month={Nov}, pages={862–870} }
 @article{berhongaray_janssens_king_ceulemans_2013, title={Fine root biomass and turnover of two fast-growing poplar genotypes in a short-rotation coppice culture}, volume={373}, ISSN={["1573-5036"]}, DOI={10.1007/s11104-013-1778-x}, abstractNote={The quantification of root dynamics remains a major challenge in ecological research because root sampling is laborious and prone to error due to unavoidable disturbance of the delicate soil-root interface. The objective of the present study was to quantify the distribution of the biomass and turnover of roots of poplars (Populus) and associated understory vegetation during the second growing season of a high-density short rotation coppice culture. Roots were manually picked from soil samples collected with a soil core from narrow (75 cm apart) and wide rows (150 cm apart) of the double-row planting system from two genetically contrasting poplar genotypes. Several methods of estimating root production and turnover were compared. Poplar fine root biomass was higher in the narrow rows than in the wide rows. In spite of genetic differences in above-ground biomass, annual fine root productivity was similar for both genotypes (ca. 44 g DM m−2 year−1). Weed root biomass was equally distributed over the ground surface, and root productivity was more than two times higher compared to poplar fine roots (ca. 109 g DM m−2 year−1). Early in SRC plantation development, weeds result in significant root competition to the crop tree poplars, but may confer certain ecosystem services such as carbon input to soil and retention of available soil N until the trees fully occupy the site.}, number={1-2}, journal={PLANT AND SOIL}, author={Berhongaray, Gonzalo and Janssens, I. A. and King, J. S. and Ceulemans, R.}, year={2013}, month={Dec}, pages={269–283} }
 @article{domec_rivera_king_peszlen_hain_smith_frampton_2013, title={Hemlock woolly adelgid (Adelges tsugae) infestation affects water and carbon relations of eastern hemlock (Tsuga canadensis) and Carolina hemlock (Tsuga caroliniana)}, volume={199}, ISSN={0028-646X 1469-8137}, url={http://dx.doi.org/10.1111/nph.12263}, DOI={10.1111/nph.12263}, abstractNote={Summary}, number={2}, journal={New Phytologist}, publisher={Wiley}, author={Domec, Jean‐Christophe and Rivera, Laura N. and King, John S. and Peszlen, Ilona and Hain, Fred and Smith, Benjamin and Frampton, John}, year={2013}, month={Apr}, pages={452–463} }
 @article{aspinwall_king_mckeand_2013, title={Productivity differences among loblolly pine genotypes are independent of individual-tree biomass partitioning and growth efficiency}, volume={27}, ISSN={["1432-2285"]}, DOI={10.1007/s00468-012-0806-4}, number={3}, journal={TREES-STRUCTURE AND FUNCTION}, author={Aspinwall, Michael J. and King, John S. and McKeand, Steven E.}, year={2013}, month={Jun}, pages={533–545} }
 @article{king_ceulemans_albaugh_dillen_domec_fichot_fischer_leggett_sucre_trnka_et al._2013, title={The Challenge of Lignocellulosic Bioenergy in a Water-Limited World}, volume={63}, ISSN={["1525-3244"]}, DOI={10.1525/bio.2013.63.2.6}, abstractNote={It is hoped that lignocellulosic sources will provide energy security, offset carbon dioxide enrichment of the atmosphere, and stimulate the development of new economic sectors. However, little is known about the productivity and sustainability of plant cell-wall energy industries. In this study, we used 16 global circulation models to project the global distribution of relative water availability in the coming decades and summarized the available data on the water-use efficiency of tree- and grass-based bioenergy systems. The data on bioenergy water use were extremely limited. Productivity was strongly correlated with water-use efficiency, with C4 grasses having a distinct advantage in this regard. Our analysis of agro climatic drivers of bioenergy productivity suggests that relative water availability will be one of the most important climatic changes to consider in the design of bioenergy systems.}, number={2}, journal={BIOSCIENCE}, author={King, John S. and Ceulemans, Reinhart and Albaugh, Janine M. and Dillen, Sophie Y. and Domec, Jean-Christophe and Fichot, Regis and Fischer, Milan and Leggett, Zakiya and Sucre, Eric and Trnka, Mirek and et al.}, year={2013}, month={Feb}, pages={102–117} }
 @article{miao_noormets_domec_trettin_mcnulty_sun_king_2013, title={The effect of water table fluctuation on soil respiration in a lower coastal plain forested wetland in the southeastern US}, volume={118}, ISSN={["2169-8961"]}, DOI={10.1002/2013jg002354}, abstractNote={Abstract}, number={4}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES}, author={Miao, Guofang and Noormets, Asko and Domec, Jean-Christophe and Trettin, Carl C. and McNulty, Steve G. and Sun, Ge and King, John S.}, year={2013}, month={Dec}, pages={1748–1762} }
 @article{domec_sun_noormets_gavazzi_treasure_cohen_swenson_mcnulty_king_2012, title={A Comparison of Three Methods to Estimate Evapotranspiration in Two Contrasting Lob lolly Pine Plantations: Age-Related Changes in Water Use and Drought Sensitivity of Evapotranspiration Components}, volume={58}, ISSN={["1938-3738"]}, DOI={10.5849/forsci.11-051}, abstractNote={Increasing variability of rainfall patterns requires detailed understanding of the pathways of water loss from ecosystems to optimize carbon uptake and management choices. In the current study we characterized the usability of three alternative methods of different rigor for quantifying stand-level evapotranspiration (ET), partitioned ET into tree transpiration (T), understory transpiration, interception, and soil evaporation (E S) and determined their sensitivity to drought, and evaluated the reliability of soil moisture measurements by taking into account deep soil moisture dynamic. The analyses were conducted in an early- and in a mid-rotation stand of loblolly pine, the predominant species of southern US forest plantations. The three alternative methods for estimating ET were the eddy covariance measurements of water vapor fluxes (ET EC), the water table fluctuation (ET WT), and the soil moisture fluctuation (ETSM). On annual and monthly scales, the three methods agreed to within 10-20%, whereas on a daily scale, the values of ET SM and ETEC differed by up to 50% and ETSM and ET WT differed by up to 100%. The differences between the methods were attributed to root water extraction below measurement depth and to the sampling at different spatial scales. Regardless of the method used, ET at the early-rotation site was 15-30% lower than that at the mid-rotation site. The dry years did not affect ET at the mid-rotation site but reduced significantly ET at the early-rotation site. Soil moisture trends revealed the importance of measuring water content at several depths throughout the rooting zone because less than 20% of the water is stored in the top 30 cm of soil. Annually, E S represented approximately 9 and 14% of ETEC at the mid-rotation site and the early-rotation site, respectively. At the mid-rotation site, T accounted for approximately 70% of ET EC. Canopy interception was estimated to be 5-10% of annual precipitation and 6-13% of total ETEC. At the early-rotation site, T accounted for only 35% of ET EC. At this site, transpiration from subdominant trees and shrubs represented 40-45% of ET EC, indicating that understory was a significant part of the water budget. We concluded that the eddy covariance method is best for estimating ET at the fine temporal scale (i.e., daily), but other soil moisture and water table-based methods were equally reliable and cost-effective for quantifying seasonal ET dynamics. FOR .S CI. 58(5):497-512.}, number={5}, journal={FOREST SCIENCE}, author={Domec, Jean-Christophe and Sun, Ge and Noormets, Asko and Gavazzi, Michael J. and Treasure, Emrys A. and Cohen, Erika and Swenson, Jennifer J. and McNulty, Steve G. and King, John S.}, year={2012}, month={Oct}, pages={497–512} }
 @article{aspinwall_mckeand_king_2012, title={Carbon Sequestration from 40 Years of Planting Genetically Improved Loblolly Pine across the Southeast United States}, volume={58}, ISSN={["1938-3738"]}, DOI={10.5849/forsci.11-058}, abstractNote={Highly productive, widely deployed genetically improved loblolly pine (Pinus taeda L.) may play an important role in mitigating rising atmospheric CO2 via carbon (C) sequestration. To understand the role of loblolly pine genetic improvement in future C sequestration strategies, we examined the historical (1968–2007) impact of operationally deploying improved families of loblolly pine on productivity and C sequestration across the southeast United States. Since 1977, nearly 100% of loblolly pine plantations in the southeast United States have been established with genetically improved loblolly pine. In recent years, more than 400,000 ha of genetically improved loblolly pine are planted annually. Between 1968 and 2007, we estimate that genetically improved loblolly pine plantations have produced a total of 25.6 billion m3 of stemwood volume and have sequestered 9,865 Tg C in live and dead biomass. Our estimates also indicate that genetic improvement has resulted in an additional 3.7 billion m3 (17% increase) and 1,100 Tg C (13%) of volume production and C sequestration, respectively, relative to volume production and C sequestration with no genetic improvement. We expect that loblolly pine plantation C sequestration will increase as more productive families and clones are deployed and as currently deployed genetic material continues to mature. Together, genetic improvement, intensive silvicultural, and longer rotations aimed at producing long-lived wood products will be important tools for maximizing C sequestration in loblolly pine plantations.}, number={5}, journal={FOREST SCIENCE}, author={Aspinwall, Michael J. and McKeand, Steven E. and King, John S.}, year={2012}, month={Oct}, pages={446–456} }
 @article{bueker_morrissey_briolat_falk_simpson_tuovinen_alonso_barth_baumgarten_grulke_et al._2012, title={DO3SE modelling of soil moisture to determine ozone flux to forest trees}, volume={12}, ISSN={["1680-7324"]}, DOI={10.5194/acp-12-5537-2012}, abstractNote={Abstract. The DO3SE (Deposition of O3 for Stomatal Exchange) model is an established tool for estimating ozone (O3) deposition, stomatal flux and impacts to a variety of vegetation types across Europe. It has been embedded within the EMEP (European Monitoring and Evaluation Programme) photochemical model to provide a policy tool capable of relating the flux-based risk of vegetation damage to O3 precursor emission scenarios for use in policy formulation. A key limitation of regional flux-based risk assessments has been the assumption that soil water deficits are not limiting O3 flux due to the unavailability of evaluated methods for modelling soil water deficits and their influence on stomatal conductance (gsto), and subsequent O3 flux.  This paper describes the development and evaluation of a method to estimate soil moisture status and its influence on gsto for a variety of forest tree species. This DO3SE soil moisture module uses the Penman-Monteith energy balance method to drive water cycling through the soil-plant-atmosphere system and empirical data describing gsto relationships with pre-dawn leaf water status to estimate the biological control of transpiration. We trial four different methods to estimate this biological control of the transpiration stream, which vary from simple methods that relate soil water content or potential directly to gsto, to more complex methods that incorporate hydraulic resistance and plant capacitance that control water flow through the plant system.  These methods are evaluated against field data describing a variety of soil water variables, gsto and transpiration data for Norway spruce (Picea abies), Scots pine (Pinus sylvestris), birch (Betula pendula), aspen (Populus tremuloides), beech (Fagus sylvatica) and holm oak (Quercus ilex) collected from ten sites across Europe and North America. Modelled estimates of these variables show consistency with observed data when applying the simple empirical methods, with the timing and magnitude of soil drying events being captured well across all sites and reductions in transpiration with the onset of drought being predicted with reasonable accuracy. The more complex methods, which incorporate hydraulic resistance and plant capacitance, perform less well, with predicted drying cycles consistently underestimating the rate and magnitude of water loss from the soil.  A sensitivity analysis showed that model performance was strongly dependent upon the local parameterisation of key model drivers such as the maximum gsto, soil texture, root depth and leaf area index. The results suggest that the simple modelling methods that relate gsto directly to soil water content and potential provide adequate estimates of soil moisture and influence on gsto such that they are suitable to be used to assess the potential risk posed by O3 to forest trees across Europe.
                    }, number={12}, journal={ATMOSPHERIC CHEMISTRY AND PHYSICS}, author={Bueker, P. and Morrissey, T. and Briolat, A. and Falk, R. and Simpson, D. and Tuovinen, J. -P. and Alonso, R. and Barth, S. and Baumgarten, M. and Grulke, N. and et al.}, year={2012}, pages={5537–5562} }
 @article{rhea_king_2012, title={Depth-dependency of trembling aspen and paper birch small-root responses to eCO(2) and eO(3)}, volume={355}, ISSN={["1573-5036"]}, DOI={10.1007/s11104-011-1094-2}, number={1-2}, journal={PLANT AND SOIL}, author={Rhea, L. K. and King, J. S.}, year={2012}, month={Jun}, pages={215–229} }
 @article{albaugh_sucre_leggett_domec_king_2012, title={Evaluation of intercropped switchgrass establishment under a range of experimental site preparation treatments in a forested setting on the Lower Coastal Plain of North Carolina, USA}, volume={46}, DOI={10.1016/j.biombioe.2012.06.029}, abstractNote={There is growing interest in using switchgrass (Panicum virgatum L.) as a biofuel crop and for its potential to sequester carbon. However, there are limited data on the establishment success of this species when grown as a forest intercrop in coastal plain settings of the U.S. Southeast. Therefore, we studied establishment success of switchgrass within experimental intercropped plots and in pure switchgrass plots in an intensively managed loblolly pine (Pinus taeda) plantation in eastern North Carolina. Pine trees were planted in the winter of 2008, and switchgrass was planted in the summer of 2009. Establishment success of switchgrass was measured over the growing season from May to October 2010, and quantified in terms of percent cover, height (cm), tiller density (number of tillers m−2), leaf area index and biomass (Mg ha−1). At the end of the growing season, pure switchgrass plots were taller than the intercropped treatments (114 ± 2 cm versus 98 ± 1 cm, respectively), but no significant treatment effects were evident in the other variables measured. Switchgrass biomass across all treatments increased from 2.65 ± 0.81 Mg ha−1 in 2009 to 4.14 ± 0.45 Mg ha−1 in 2010. There was no significant effect of distance from the pine row on any switchgrass growth parameters. However, we anticipate a shading effect over time that may limit switchgrass growth as the pines approach stand closure.}, journal={Biomass and Bioenergy}, author={Albaugh, J. M. and Sucre, E. B. and Leggett, Zakiya H and Domec, J. C. and King, J. S.}, year={2012}, pages={673–682} }
 @article{domec_ogee_noormets_jouangy_gavazzi_treasure_sun_mcnulty_king_2012, title={Interactive effects of nocturnal transpiration and climate change on the root hydraulic redistribution and carbon and water budgets of southern United States pine plantations}, volume={32}, ISSN={["1758-4469"]}, DOI={10.1093/treephys/tps018}, abstractNote={Deep root water uptake and hydraulic redistribution (HR) have been shown to play a major role in forest ecosystems during drought, but little is known about the impact of climate change, fertilization and soil characteristics on HR and its consequences on water and carbon fluxes. Using data from three mid-rotation loblolly pine plantations, and simulations with the process-based model MuSICA, this study indicated that HR can mitigate the effects of soil drying and had important implications for carbon uptake potential and net ecosystem exchange (NEE), especially when N fertilization is considered. At the coastal site (C), characterized by deep organic soil, HR increased dry season tree transpiration (T) by up to 40%, and such an increase affected NEE through major changes in gross primary productivity (GPP). Deep-rooted trees did not necessarily translate into a large volume of HR unless soil texture allowed large water potential gradients to occur, as was the case at the sandy site (S). At the Piedmont site (P) characterized by a shallow clay-loam soil, HR was low but not negligible, representing up to 10% of T. In the absence of HR, it was predicted that at the C, S and P sites, annual GPP would have been diminished by 19, 7 and 9%, respectively. Under future climate conditions HR was predicted to be reduced by up to 25% at the C site, reducing the resilience of trees to precipitation deficits. The effect of HR on T and GPP was predicted to diminish under future conditions by 12 and 6% at the C and P sites, respectively. Under future conditions, T was predicted to stay the same at the P site, but to be marginally reduced at the C site and slightly increased at the S site. Future conditions and N fertilization would decrease T by 25% at the C site, by 15% at the P site and by 8% at the S site. At the C and S sites, GPP was estimated to increase by 18% and by >70% under future conditions, respectively, with little effect of N fertilization. At the P site, future conditions would stimulate GPP by only 12%, but future conditions plus N fertilization would increase GPP by 24%. As a consequence, in all sites, water use efficiency was predicted to improve dramatically with future conditions. Modeling the effect of reduced annual precipitation indicated that limited water availability would decrease all carbon fluxes, including NEE and respiration. Our simulations highlight the interactive effects of nutrients and elevated CO(2), and showed that the effect of N fertilization would be greater under future climate conditions.}, number={6}, journal={TREE PHYSIOLOGY}, author={Domec, Jean-Christophe and Ogee, Jerome and Noormets, Asko and Jouangy, Julien and Gavazzi, Michael and Treasure, Emrys and Sun, Ge and McNulty, Steve G. and King, John S.}, year={2012}, month={Jun}, pages={707–723} }
 @misc{dieleman_vicca_dijkstra_hagedorn_hovenden_larsen_morgan_volder_beier_dukes_et al._2012, title={Simple additive effects are rare: a quantitative review of plant biomass and soil process responses to combined manipulations of CO2 and temperature}, volume={18}, ISSN={["1365-2486"]}, DOI={10.1111/j.1365-2486.2012.02745.x}, abstractNote={Abstract}, number={9}, journal={GLOBAL CHANGE BIOLOGY}, author={Dieleman, Wouter I. J. and Vicca, Sara and Dijkstra, Feike A. and Hagedorn, Frank and Hovenden, Mark J. and Larsen, Klaus S. and Morgan, Jack A. and Volder, Astrid and Beier, Claus and Dukes, Jeffrey S. and et al.}, year={2012}, month={Sep}, pages={2681–2693} }
 @article{noormets_mcnulty_domec_gavazzi_sun_king_2012, title={The role of harvest residue in rotation cycle carbon balance in loblolly pine plantations. Respiration partitioning approach}, volume={18}, ISSN={["1354-1013"]}, DOI={10.1111/j.1365-2486.2012.02776.x}, abstractNote={Abstract}, number={10}, journal={GLOBAL CHANGE BIOLOGY}, author={Noormets, Asko and McNulty, Steve G. and Domec, Jean-Christophe and Gavazzi, Michael and Sun, Ge and King, John S.}, year={2012}, month={Oct}, pages={3186–3201} }
 @article{onandia_olsson_barth_king_uddling_2011, title={Exposure to moderate concentrations of tropospheric ozone impairs tree stomatal response to carbon dioxide}, volume={159}, ISSN={["1873-6424"]}, DOI={10.1016/j.envpol.2011.06.001}, abstractNote={With rising concentrations of both atmospheric carbon dioxide (CO2) and tropospheric ozone (O3), it is important to better understand the interacting effects of these two trace gases on plant physiology affecting land-atmosphere gas exchange. We investigated the effect of growth under elevated CO2 and O3, singly and in combination, on the primary short-term stomatal response to CO2 concentration in paper birch at the Aspen FACE experiment. Leaves from trees grown in elevated CO2 and/or O3 exhibited weaker short-term responses of stomatal conductance to both an increase and a decrease in CO2 concentration from current ambient level. The impairement of the stomatal CO2 response by O3 most likely developed progressively over the growing season as assessed by sap flux measurements. Our results suggest that expectations of plant water-savings and reduced stomatal air pollution uptake under rising atmospheric CO2 may not hold for northern hardwood forests under concurrently rising tropospheric O3.}, number={10}, journal={ENVIRONMENTAL POLLUTION}, author={Onandia, Gabriela and Olsson, Anna-Karin and Barth, Sabine and King, John S. and Uddling, Johan}, year={2011}, month={Oct}, pages={2350–2354} }
 @article{aspinwall_king_mckeand_bullock_2011, title={Genetic effects on stand-level uniformity and above- and belowground dry mass production in juvenile loblolly pine}, volume={262}, ISSN={["1872-7042"]}, DOI={10.1016/j.foreco.2011.04.029}, abstractNote={Genetic differences in stand-level above- and belowground dry mass production in loblolly pine (Pinus taeda L.) may influence southern pine plantation productivity, sustainability and carbon (C) sequestration. Furthermore, deployment of more or less genetically homogeneous individuals could impact stand uniformity and ecosystem processes. In this study, we aimed to compare stand uniformity and above- and belowground dry mass production among loblolly pine genotypes of contrasting inherent genetic homogeneity. We hypothesized that stand-level uniformity would increase as within-genotype inherent genetic variation decreased (open-pollinated (half-sib) > full-sib > clone). To examine genetic effects on stand uniformity and productivity, we grew ten different genotypes (three open-pollinated families, three full-sib families, three clones, and one seed orchard mix variety) in a plantation setting for 4 years, at two different planting densities (∼539 and 1077 trees ha−1), and used allometric relationships to estimate standing dry mass and annual dry mass production. In the low planting density treatment, age 3 total standing dry mass of the most productive genotype (5824 kg ha−1) was 82% higher than that of the least productive genotype (3207 kg ha−1). In the high planting density treatment, age 3 total standing dry mass of the most productive genotype (11,393 kg ha−1) was 110% higher than that of the least productive genotype (5427 kg ha−1). Genetic differences in annual dry mass production were of a similar magnitude with peak rates during the third year as high as 4221 and 8198 kg ha−1 yr−1 in the low and high planting density treatments, respectively. More genetically homogeneous genotypes did not show greater stand-level uniformity under operational management conditions. Over time, genotypes showed no consistent differences in the coefficient of variation (CV) for ground-level diameter; however, two full-sib and two half-sib families showed significantly lower CV’s for total tree height than all three clones. Moreover, genotypes with lower CV’s for height growth displayed greater stand-level dry mass production which supports the premise that greater stand uniformity will lead to enhanced productivity. Since uniformity and stand-level productivity of loblolly pine clones will be principally governed by environmental heterogeneity, our results highlight the need for silvicultural prescriptions that maximize site uniformity. In addition, our results demonstrate how the deployment of highly productive loblolly pine genotypes may provide a means of enhancing southern pine ecosystem sustainability by sequestering C in both harvestable aboveground biomass and woody belowground biomass.}, number={4}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Aspinwall, Michael J. and King, John S. and McKeand, Steven E. and Bullock, Bronson P.}, year={2011}, month={Aug}, pages={609–619} }
 @article{aspinwall_king_booker_mckeand_2011, title={Genetic effects on total phenolics, condensed tannins and non-structural carbohydrates in loblolly pine (Pinus taeda L.) needles}, volume={31}, ISSN={["1758-4469"]}, DOI={10.1093/treephys/tpr073}, abstractNote={Carbon allocation to soluble phenolics (total phenolics, proanthocyanidins (PA)) and total non-structural carbohydrates (TNC; starch and soluble sugars) in needles of widely planted, highly productive loblolly pine (Pinus taeda L.) genotypes could impact stand resistance to herbivory, and biogeochemical cycling in the southeastern USA. However, genetic and growth-related effects on loblolly pine needle chemistry are not well characterized. Therefore, we investigated genetic and growth-related effects on foliar concentrations of total phenolics, PA and TNC in two different field studies. The first study contained nine different genotypes representing a range of genetic homogeneity, growing in a 2-year-old plantation on the coastal plain of North Carolina (NC), USA. The second study contained eight clones with different growth potentials planted in a 9-year-old clonal trial replicated at two sites (Georgia (GA) and South Carolina (SC), USA). In the first study (NC), we found no genetic effects on total phenolics, PA and TNC, and there was no relationship between genotype size and foliar biochemistry. In the second study, there were no differences in height growth between sites, but the SC site showed greater diameter (diameter at breast height (DBH)) and volume, most likely due to greater tree mortality (lower stocking) which reduced competition for resources and increased growth of remaining trees. We found a significant site × clone effect for total phenolics with lower productivity clones showing 27-30% higher total phenolic concentrations at the GA site where DBH and volume were lower. In contrast to the predictions of growth-defense theory, clone volume was positively associated with total phenolic concentrations at the higher volume SC site, and PA concentrations at the lower volume GA site. Overall, we found no evidence of a trade-off between genotype size and defense, and genetic potential for improved growth may include increased allocation to some secondary metabolites. These results imply that deployment of more productive loblolly pine genotypes will not reduce stand resistance to herbivory, but increased production of total phenolics and PA associated with higher genotype growth potential could reduce litter decomposition rates and therefore, nutrient availability.}, number={8}, journal={TREE PHYSIOLOGY}, author={Aspinwall, Michael J. and King, John S. and Booker, Fitzgerald L. and McKeand, Steven E.}, year={2011}, month={Aug}, pages={831–842} }
 @article{aspinwall_king_domec_mckeand_isik_2011, title={Genetic effects on transpiration, canopy conductance, stomatal sensitivity to vapour pressure deficit, and cavitation resistance in loblolly pine}, volume={4}, ISSN={1936-0584}, url={http://dx.doi.org/10.1002/eco.197}, DOI={10.1002/eco.197}, abstractNote={Abstract}, number={2}, journal={Ecohydrology}, publisher={Wiley}, author={Aspinwall, Michael J. and King, John S. and Domec, Jean-Christophe and McKeand, Steven E. and Isik, Fikret}, year={2011}, month={Jan}, pages={168–182} }
 @article{aspinwall_king_mckeand_domec_2011, title={Leaf-level gas-exchange uniformity and photosynthetic capacity among loblolly pine (Pinus taeda L.) genotypes of contrasting inherent genetic variation}, volume={31}, ISSN={["1758-4469"]}, DOI={10.1093/treephys/tpq107}, abstractNote={Variation in leaf-level gas exchange among widely planted genetically improved loblolly pine (Pinus taeda L.) genotypes could impact stand-level water use, carbon assimilation, biomass production, C allocation, ecosystem sustainability and biogeochemical cycling under changing environmental conditions. We examined uniformity in leaf-level light-saturated photosynthesis (A(sat)), stomatal conductance (g(s)), and intrinsic water-use efficiency (A(sat)/g(s) or δ) among nine loblolly pine genotypes (selected individuals): three clones, three full-sib families and three half-sib families, during the early years of stand development (first 3 years), with each genetic group possessing varying amounts of inherent genetic variation. We also compared light- and CO(2)-response parameters between genotypes and examined the relationship between genotype productivity, gas exchange and photosynthetic capacity. Within full-sib, half-sib and clonal genotypes, the coefficient of variation (CV) for gas exchange showed no consistent pattern; the CV for g(s) and δ was similar within clonal (44.3-46.9 and 35.5-38.6%) and half-sib (41.0-49.3 and 36.8-40.9%) genotypes, while full-sibs showed somewhat higher CVs (46.9-56.0 and 40.1-45.4%). In contrast, the CVs for A(sat) were generally higher within clones. With the exception of δ, differences in gas exchange among genotypes were generally insignificant. Tree volume showed a significant positive correlation with A(sat) and δ, but the relationship varied by season. Individual-tree volume and genotype volume were positively correlated with needle dark respiration (R(d)). Our results suggest that uniformity in leaf-level physiological rates is not consistently related to the amount of genetic variation within a given genotype, and δ, A(sat) and R(d) were the leaf-level physiological parameters that were most consistently related to individual-tree and genotype productivity. An enhanced understanding of molecular and environmental factors that influence physiological variation within and between loblolly pine genotypes may improve assessments of genotype growth potential and sensitivity to global climate change.}, number={1}, journal={TREE PHYSIOLOGY}, author={Aspinwall, Michael J. and King, John S. and McKeand, Steven E. and Domec, Jean-Christophe}, year={2011}, month={Jan}, pages={78–91} }
 @misc{calfapietra_ainsworth_beier_de angelis_ellsworth_godbold_hendrey_hickler_hoosbeek_karnosky_et al._2010, title={Challenges in elevated CO2 experiments on forests}, volume={15}, ISSN={["1878-4372"]}, DOI={10.1016/j.tplants.2009.11.001}, abstractNote={Current forest Free Air CO2 Enrichment (FACE) experiments are reaching completion. Therefore, it is time to define the scientific goals and priorities of future experimental facilities. In this opinion article, we discuss the following three overarching issues (i) What are the most urgent scientific questions and how can they be addressed? (ii) What forest ecosystems should be investigated? (iii) Which other climate change factors should be coupled with elevated CO2 concentrations in future experiments to better predict the effects of climate change? Plantations and natural forests can have conflicting purposes for high productivity and environmental protection. However, in both cases the assessment of carbon balance and how this will be affected by elevated CO2 concentrations and the interacting climate change factors is the most pressing priority for future experiments. Current forest Free Air CO2 Enrichment (FACE) experiments are reaching completion. Therefore, it is time to define the scientific goals and priorities of future experimental facilities. In this opinion article, we discuss the following three overarching issues (i) What are the most urgent scientific questions and how can they be addressed? (ii) What forest ecosystems should be investigated? (iii) Which other climate change factors should be coupled with elevated CO2 concentrations in future experiments to better predict the effects of climate change? Plantations and natural forests can have conflicting purposes for high productivity and environmental protection. However, in both cases the assessment of carbon balance and how this will be affected by elevated CO2 concentrations and the interacting climate change factors is the most pressing priority for future experiments.}, number={1}, journal={TRENDS IN PLANT SCIENCE}, author={Calfapietra, Carlo and Ainsworth, Elizabeth A. and Beier, Claus and De Angelis, Paolo and Ellsworth, David S. and Godbold, Douglas L. and Hendrey, George R. and Hickler, Thomas and Hoosbeek, Marcel R. and Karnosky, David F. and et al.}, year={2010}, month={Jan}, pages={5–10} }
 @article{noormets_sun_mcnulty_gavazzi_chen_domec_king_amatya_skaggs_2010, title={Corrigendum: “Energy and water balance of two contrasting loblolly pine plantations on the lower coastal plain of North Carolina, USA” [Foreco 259: 1299–1310]}, volume={260}, ISSN={0378-1127}, url={http://dx.doi.org/10.1016/j.foreco.2010.04.007}, DOI={10.1016/j.foreco.2010.04.007}, abstractNote={In Sun et al. (2010) we reported the albedos (A) for two loblolly pine plantations in the range of 0.22?0.38 (Table 5 in Sun et al., 2010).}, number={1}, journal={Forest Ecology and Management}, publisher={Elsevier BV}, author={Noormets, A. and Sun, G. and McNulty, S.G. and Gavazzi, M.J. and Chen, J. and Domec, J.-C. and King, J.S. and Amatya, D.M. and Skaggs, R.W.}, year={2010}, month={Jun}, pages={169} }
 @article{king_percy_matyssek_2010, title={Dedication to Dr. David F. Karnosky}, volume={158}, ISSN={["0269-7491"]}, DOI={10.1016/j.envpol.2009.11.018}, number={4}, journal={ENVIRONMENTAL POLLUTION}, author={King, John S. and Percy, Kevin E. and Matyssek, Rainer}, year={2010}, month={Apr}, pages={953–954} }
 @article{rhea_king_kubiske_saliendra_teclaw_2010, title={Effects of elevated atmospheric CO2 and tropospheric O-3 on tree branch growth and implications for hydrologic budgeting}, volume={158}, ISSN={["0269-7491"]}, DOI={10.1016/j.envpol.2009.08.038}, abstractNote={The forest hydrologic budget may be impacted by increasing CO2 and tropospheric O3. Efficient means to quantify such effects are beneficial. We hypothesized that changes in the balance of canopy interception, stem flow, and through-fall in the presence of elevated CO2 and O3 could be discerned using image analysis of leafless branches. We compared annual stem flow to the results of a computerized analysis of all branches from the 2002, 2004, and 2006 annual growth whorls of 97 ten-year-old trees from the Aspen Free-Air CO2 and O3 Enrichment (Aspen FACE) experiment in Rhinelander, WI. We found significant effects of elevated CO2 and O3 on some branch metrics, and that the branch metrics were useful for predicting stem flow from birch, but not aspen. The results of this study should contribute to development of techniques for efficient characterization of effects on the forest hydrologic budget of increasing CO2 and tropospheric O3.}, number={4}, journal={ENVIRONMENTAL POLLUTION}, author={Rhea, L. and King, J. and Kubiske, M. and Saliendra, N. and Teclaw, R.}, year={2010}, month={Apr}, pages={1079–1087} }
 @article{sun_noormets_gavazzi_mcnulty_chen_domec_king_amatya_skaggs_2010, title={Energy and water balance of two contrasting loblolly pine plantations on the lower coastal plain of North Carolina, USA}, volume={259}, ISSN={["1872-7042"]}, DOI={10.1016/j.foreco.2009.09.016}, abstractNote={During 2005–2007, we used the eddy covariance and associated hydrometric methods to construct energy and water budgets along a chronosequence of loblolly pine (Pinus taeda) plantations that included a mid-rotation stand (LP) (i.e., 13–15 years old) and a recently established stand on a clearcut site (CC) (i.e., 4–6 years old) in Eastern North Carolina. Our central objective was to quantify the differences in both energy and water balances between the two contrasting stands and understand the underlining mechanisms of environmental controls. We found that the LP site received about 20% more net radiation (Rn) due to its lower averaged albedo (α) of 0.25, compared with that at the CC (α = 0.34). The mean monthly averaged Bowen ratios (β) at the LP site were 0.89 ± 0.7, significantly (p = 0.02) lower than at the CC site (1.45 ± 1.2). Higher net radiation resulted in a 28% higher (p = 0.02) latent heat flux (LE) for ecosystem evapotranspiration at the LP site, but there was no difference in sensible heat flux (H) between the two contrasting sites. The annual total evapotranspiration (ET) at the LP site and CC site was estimated as 1011–1226 and 755–855 mm year−1, respectively. The differences in ET rates between the two contrasting sites occurred mostly during the non-growing seasons and/or dry periods, and they were small during peak growing seasons or wet periods. Higher net radiation and biomass in LP were believed to be responsible to the higher ET. The monthly ET/Grass Reference ET ratios differed significantly across site and season. The annual ET/P ratio for the LP and CC were estimated as 0.70–1.13 and 0.60–0.88, respectively, indicating higher runoff production from the CC site than the LP site. This study implied that reforestation practices reduced surface albedos and thus increased available energy, but they did not necessarily increase energy for warming the atmosphere in the coastal plain region where soil water was generally not limited. This study showed the highly variable response of energy and water balances to forest management due to climatic variability.}, number={7}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Sun, G. and Noormets, A. and Gavazzi, M. J. and McNulty, S. G. and Chen, J. and Domec, J. -C. and King, J. S. and Amatya, D. M. and Skaggs, R. W.}, year={2010}, month={Mar}, pages={1299–1310} }
 @article{noormets_sun_mcnulty_gavazzi_chen_domec_king_amatya_skaggs_2010, title={Energy and water balance of two contrasting loblolly pine plantations on the lower coastal plain of North Carolina, USA (vol 259, pg 1299, 2010)}, volume={260}, number={1}, journal={Forest Ecology and Management}, author={Noormets, A. and Sun, G. and McNulty, S. G. and Gavazzi, M. J. and Chen, J. and Domec, J. C. and King, J. S. and Amatya, D. M. and Skaggs, R. W.}, year={2010}, pages={169–169} }
 @article{percy_matyssek_king_2010, title={Facing the Future: Evidence from Joint Aspen FACE, SoyFACE and SFB 607 Meeting}, volume={158}, ISSN={["1873-6424"]}, DOI={10.1016/j.envpol.2009.11.017}, number={4}, journal={ENVIRONMENTAL POLLUTION}, author={Percy, Kevin E. and Matyssek, Rainer and King, John S.}, year={2010}, month={Apr}, pages={955–958} }
 @article{domec_king_noormets_treasure_gavazzi_sun_mcnulty_2010, title={Hydraulic redistribution of soil water by roots affects whole-stand evapotranspiration and net ecosystem carbon exchange}, volume={187}, ISSN={["1469-8137"]}, DOI={10.1111/j.1469-8137.2010.03245.x}, abstractNote={
            Commentary p 3
          }, number={1}, journal={NEW PHYTOLOGIST}, author={Domec, Jean-Christophe and King, John S. and Noormets, Asko and Treasure, Emrys and Gavazzi, Michael J. and Sun, Ge and McNulty, Steven G.}, year={2010}, pages={171–183} }
 @article{noormets_gavazzi_mcnulty_domec_sun_king_chen_2010, title={Response of carbon fluxes to drought in a coastal plain loblolly pine forest}, volume={16}, ISSN={["1365-2486"]}, DOI={10.1111/j.1365-2486.2009.01928.x}, abstractNote={Abstract}, number={1}, journal={GLOBAL CHANGE BIOLOGY}, author={Noormets, Asko and Gavazzi, Michael J. and Mcnulty, Steve G. and Domec, Jean-Christophe and Sun, Ge and King, John S. and Chen, Jiquan}, year={2010}, month={Jan}, pages={272–287} }
 @article{domec_noormets_king_sun_mcnulty_gavazzi_boggs_treasure_2009, title={Decoupling the influence of leaf and root hydraulic conductances on stomatal conductance and its sensitivity to vapour pressure deficit as soil dries in a drained loblolly pine plantation}, volume={32}, ISSN={["1365-3040"]}, DOI={10.1111/j.1365-3040.2009.01981.x}, abstractNote={ABSTRACT}, number={8}, journal={PLANT CELL AND ENVIRONMENT}, author={Domec, Jean-Christophe and Noormets, Asko and King, John S. and Sun, Ge and McNulty, Steven G. and Gavazzi, Michael J. and Boggs, Johnny L. and Treasure, Emrys A.}, year={2009}, month={Aug}, pages={980–991} }
 @article{liu_king_booker_giardina_allen_hu_2009, title={Enhanced litter input rather than changes in litter chemistry drive soil carbon and nitrogen cycles under elevated CO2: a microcosm study}, volume={15}, ISSN={["1365-2486"]}, DOI={10.1111/j.1365-2486.2008.01747.x}, abstractNote={Abstract}, number={2}, journal={GLOBAL CHANGE BIOLOGY}, author={Liu, Lingli and King, John S. and Booker, Fitzgerald L. and Giardina, Christian P. and Allen, H. Lee and Hu, Shuijin}, year={2009}, month={Feb}, pages={441–453} }
 @article{liu_king_giardina_booker_2009, title={The influence of chemistry, production and community composition on leaf litter decomposition under elevated atmospheric CO2 and tropospheric O-3 in a northern hardwood ecosystem}, volume={12}, ISBN={1432-9840}, DOI={10.1007/s10021-009-9231-y}, number={3}, journal={Ecosystems}, author={Liu, L. L. and King, J. S. and Giardina, C. P. and Booker, F. L.}, year={2009}, pages={401–416} }
 @article{pregitzer_burton_king_zak_2008, title={Soil respiration, root biomass, and root turnover following long-term exposure of northern forests to elevated atmospheric Co-2 and tropospheric O-3}, volume={180}, ISSN={["1469-8137"]}, DOI={10.1111/j.1469-8137.2008.02564.x}, abstractNote={The Rhinelander free-air CO(2) enrichment (FACE) experiment is designed to understand ecosystem response to elevated atmospheric carbon dioxide (+CO(2)) and elevated tropospheric ozone (+O(3)). The objectives of this study were: to understand how soil respiration responded to the experimental treatments; to determine whether fine-root biomass was correlated to rates of soil respiration; and to measure rates of fine-root turnover in aspen (Populus tremuloides) forests and determine whether root turnover might be driving patterns in soil respiration. Soil respiration was measured, root biomass was determined, and estimates of root production, mortality and biomass turnover were made. Soil respiration was greatest in the +CO(2) and +CO(2) +O(3) treatments across all three plant communities. Soil respiration was correlated with increases in fine-root biomass. In the aspen community, annual fine-root production and mortality (g m(-2)) were positively affected by +O(3). After 10 yr of exposure, +CO(2) +O(3)-induced increases in belowground carbon allocation suggest that the positive effects of elevated CO(2) on belowground net primary productivity (NPP) may not be offset by negative effects of O(3). For the aspen community, fine-root biomass is actually stimulated by +O(3), and especially +CO(2) +O(3).}, number={1}, journal={NEW PHYTOLOGIST}, author={Pregitzer, Kurt S. and Burton, Andrew J. and King, John S. and Zak, Donald R.}, year={2008}, month={Oct}, pages={153–161} }
 @misc{zak_holmes_pregitzer_king_ellsworth_kubiske_2007, title={Belowground competition and the response of developing forest communities to atmospheric CO2 and O-3}, volume={13}, ISSN={["1354-1013"]}, DOI={10.1111/j.1365-2486.2007.01436.x}, abstractNote={Abstract}, number={10}, journal={GLOBAL CHANGE BIOLOGY}, author={Zak, Donald R. and Holmes, William E. and Pregitzer, Kurt S. and King, John S. and Ellsworth, David S. and Kubiske, Mark E.}, year={2007}, month={Oct}, pages={2230–2238} }
 @article{king_giardina_pregitzer_friend_2007, title={Biomass partitioning in red pine (Pinus resinosa) along a chronosequence in the Upper Peninsula of Michigan}, volume={37}, ISSN={["1208-6037"]}, DOI={10.1139/X06-217}, abstractNote={ Carbon (C) allocation to the perennial coarse-root system of trees contributes to ecosystem C sequestration through formation of long-lived live wood biomass and, following senescence, by providing a large source of nutrient-poor detrital C. Our understanding of the controls on C allocation to coarse-root growth is rudimentary, but it has important implications for projecting belowground net primary production responses to global change. Age-related changes in C allocation to coarse roots represent a critical uncertainty for modeling landscape-scale C storage and cycling. We used a 55 year chronosequence approach with complete above- and below-ground harvests to assess the effects of stand development on biomass partitioning in red pine (Pinus resinosa Ait.), a commercially important pine species. Averaged within site, individual-tree root/shoot ratios were dynamic across stand development, changing from 0.17 at 2-, 3-, and 5-year-old sites, to 0.80 at the 8-year-old site, to 0.29 at the 55-year-old site. The results of our study suggest that a current research challenge is to determine the generality of patterns of root-shoot biomass partitioning through stand development for both coniferous and hardwood forest types, and to document how these patterns change as a function of stand age, tree size, environment, and management. }, number={1}, journal={CANADIAN JOURNAL OF FOREST RESEARCH}, author={King, J. S. and Giardina, C. P. and Pregitzer, K. S. and Friend, A. L.}, year={2007}, month={Jan}, pages={93–102} }
 @article{liu_king_giardina_2007, title={Effects of elevated atmospheric CO2 and tropospheric O-3 on nutrient dynamics: decomposition of leaf litter in trembling aspen and paper birch communities}, volume={299}, ISSN={["1573-5036"]}, DOI={10.1007/s11104-007-9361-y}, number={1-2}, journal={PLANT AND SOIL}, author={Liu, Lingli and King, John S. and Giardina, Christian P.}, year={2007}, month={Oct}, pages={65–82} }
 @article{holmes_zak_pregitzer_king_2006, title={Elevated CO2 and O-3 alter soil nitrogen transformations beneath trembling aspen, paper birch, and sugar maple}, volume={9}, ISSN={["1435-0629"]}, DOI={10.1007/s10021-006-0163-5}, number={8}, journal={ECOSYSTEMS}, author={Holmes, William E. and Zak, Donald R. and Pregitzer, Kurt S. and King, John S.}, year={2006}, month={Dec}, pages={1354–1363} }
 @article{king_pregitzer_zak_holmes_schmidt_2005, title={Fine root chemistry and decomposition in model communities of north-temperate tree species show little response to elevated atmospheric CO2 and varying soil resource availability}, volume={146}, ISSN={0029-8549}, url={http://dx.doi.org/10.1007/s00442-005-0191-4}, DOI={10.1007/s00442-005-0191-4}, abstractNote={Rising atmospheric [CO2] has the potential to alter soil carbon (C) cycling by increasing the content of recalcitrant constituents in plant litter, thereby decreasing rates of decomposition. Because fine root turnover constitutes a large fraction of annual NPP, changes in fine root decomposition are especially important. These responses will likely be affected by soil resource availability and the life history characteristics of the dominant tree species. We evaluated the effects of elevated atmospheric [CO2] and soil resource availability on the production and chemistry, mycorrhizal colonization, and decomposition of fine roots in an early- and late-successional tree species that are economically and ecologically important in north temperate forests. Open-top chambers were used to expose young trembling aspen (Populus tremuloides) and sugar maple (Acer saccharum) trees to ambient (36 Pa) and elevated (56 Pa) atmospheric CO2. Soil resource availability was composed of two treatments that bracketed the range found in the Upper Lake States, USA. After 2.5 years of growth, sugar maple had greater fine root standing crop due to relatively greater allocation to fine roots (30% of total root biomass) relative to aspen (7% total root biomass). Relative to the low soil resources treatment, aspen fine root biomass increased 76% with increased soil resource availability, but only under elevated [CO2]. Sugar maple fine root biomass increased 26% with increased soil resource availability (relative to the low soil resources treatment), and showed little response to elevated [CO2]. Concentrations of N and soluble phenolics, and C/N ratio in roots were similar for the two species, but aspen had slightly higher lignin and lower condensed tannins contents compared to sugar maple. As predicted by source-sink models of carbon allocation, pooled constituents (C/N ratio, soluble phenolics) increased in response to increased relative carbon availability (elevated [CO2]/low soil resource availability), however, biosynthetically distinct compounds (lignin, starch, condensed tannins) did not always respond as predicted. We found that mycorrhizal colonization of fine roots was not strongly affected by atmospheric [CO2] or soil resource availability, as indicated by root ergosterol contents. Overall, absolute changes in root chemical composition in response to increases in C and soil resource availability were small and had no effect on soil fungal biomass or specific rates of fine root decomposition. We conclude that root contributions to soil carbon cycling will mainly be influenced by fine root production and turnover responses to rising atmospheric [CO2], rather than changes in substrate chemistry.}, number={2}, journal={Oecologia}, publisher={Springer Science and Business Media LLC}, author={King, J. S. and Pregitzer, K. S. and Zak, D. R. and Holmes, W. E. and Schmidt, K.}, year={2005}, month={Jul}, pages={318–328} }
 @article{norby_delucia_gielen_calfapietra_giardina_king_ledford_mccarthy_moore_ceulemans_et al._2005, title={Forest response to elevated CO2 is conserved across a broad range of productivity}, volume={102}, ISSN={["0027-8424"]}, DOI={10.1073/pnas.0509478102}, abstractNote={Climate change predictions derived from coupled carbon-climate models are highly dependent on assumptions about feedbacks between the biosphere and atmosphere. One critical feedback occurs if C uptake by the biosphere increases in response to the fossil-fuel driven increase in atmospheric [CO2] (“CO2fertilization”), thereby slowing the rate of increase in atmospheric [CO2]. Carbon exchanges between the terrestrial biosphere and atmosphere are often first represented in models as net primary productivity (NPP). However, the contribution of CO2fertilization to the future global C cycle has been uncertain, especially in forest ecosystems that dominate global NPP, and models that include a feedback between terrestrial biosphere metabolism and atmospheric [CO2] are poorly constrained by experimental evidence. We analyzed the response of NPP to elevated CO2(≈550 ppm) in four free-air CO2enrichment experiments in forest stands. We show that the response of forest NPP to elevated [CO2] is highly conserved across a broad range of productivity, with a stimulation at the median of 23 ± 2%. At low leaf area indices, a large portion of the response was attributable to increased light absorption, but as leaf area indices increased, the response to elevated [CO2] was wholly caused by increased light-use efficiency. The surprising consistency of response across diverse sites provides a benchmark to evaluate predictions of ecosystem and global models and allows us now to focus on unresolved questions about carbon partitioning and retention, and spatial variation in NPP response caused by availability of other growth limiting resources.}, number={50}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, author={Norby, RJ and DeLucia, EH and Gielen, B and Calfapietra, C and Giardina, CP and King, JS and Ledford, J and McCarthy, HR and Moore, DJP and Ceulemans, R and et al.}, year={2005}, month={Dec}, pages={18052–18056} }
 @article{karberg_pregitzer_king_friend_wood_2005, title={Soil carbon dioxide partial pressure and dissolved inorganic carbonate chemistry under elevated carbon dioxide and ozone}, volume={142}, ISSN={0029-8549 1432-1939}, url={http://dx.doi.org/10.1007/s00442-004-1665-5}, DOI={10.1007/s00442-004-1665-5}, abstractNote={Global emissions of atmospheric CO(2) and tropospheric O(3) are rising and expected to impact large areas of the Earth's forests. While CO(2) stimulates net primary production, O(3) reduces photosynthesis, altering plant C allocation and reducing ecosystem C storage. The effects of multiple air pollutants can alter belowground C allocation, leading to changes in the partial pressure of CO(2) (pCO(2)) in the soil , chemistry of dissolved inorganic carbonate (DIC) and the rate of mineral weathering. As this system represents a linkage between the long- and short-term C cycles and sequestration of atmospheric CO(2), changes in atmospheric chemistry that affect net primary production may alter the fate of C in these ecosystems. To date, little is known about the combined effects of elevated CO(2) and O(3) on the inorganic C cycle in forest systems. Free air CO(2) and O(3) enrichment (FACE) technology was used at the Aspen FACE project in Rhinelander, Wisconsin to understand how elevated atmospheric CO(2) and O(3) interact to alter pCO(2) and DIC concentrations in the soil. Ambient and elevated CO(2) levels were 360+/-16 and 542+/-81 microl l(-1), respectively; ambient and elevated O(3) levels were 33+/-14 and 49+/-24 nl l(-1), respectively. Measured concentrations of soil CO(2) and calculated concentrations of DIC increased over the growing season by 14 and 22%, respectively, under elevated atmospheric CO(2) and were unaffected by elevated tropospheric O(3). The increased concentration of DIC altered inorganic carbonate chemistry by increasing system total alkalinity by 210%, likely due to enhanced chemical weathering. The study also demonstrated the close coupling between the seasonal delta(13)C of soil pCO(2) and DIC, as a mixing model showed that new atmospheric CO(2) accounted for approximately 90% of the C leaving the system as DIC. This study illustrates the potential of using stable isotopic techniques and FACE technology to examine long- and short-term ecosystem C sequestration.}, number={2}, journal={Oecologia}, publisher={Springer Science and Business Media LLC}, author={Karberg, N. J. and Pregitzer, K. S. and King, J. S. and Friend, A. L. and Wood, J. R.}, year={2005}, pages={296–306} }
 @article{king_kubiske_pregitzer_hendrey_mcdonald_giardina_quinn_karnosky_2005, title={Tropospheric O-3 compromises net primary production in young stands of trembling aspen, paper birch and sugar maple in response to elevated atmospheric CO2}, volume={168}, ISSN={["1469-8137"]}, DOI={10.1111/j.1469-8137.2005.01557.x}, abstractNote={Summary • Concentrations of atmospheric CO 2 and tropospheric ozone (O 3 ) are rising concurrently in the atmosphere, with potentially antagonistic effects on forest net primary production (NPP) and implications for terrestrial carbon sequestration. • Using free-air CO 2 enrichment (FACE) technology, we exposed north-temperate forest communities to concentrations of CO 2 and O 3 predicted for the year 2050 for the first 7 yr of stand development. Site-specific allometric equations were applied to annual nondestructive growth measurements to estimate above- and below-ground biomass and NPP for each year of the experiment. • Relative to the control, elevated CO 2 increased total biomass 25, 45 and 60% in the aspen, aspen‐birch and aspen‐maple communities, respectively. Tropospheric O 3 caused 23, 13 and 14% reductions in total biomass relative to the control in the respective communities. Combined fumigation resulted in total biomass response of − 7.8, +8.4 and +24.3% relative to the control in the aspen, aspen‐birch and aspen‐ sugar maple communities, respectively. • These results indicate that exposure to even moderate levels of O 3 significantly reduce the capacity of NPP to respond to elevated CO 2 in some forests.}, number={3}, journal={NEW PHYTOLOGIST}, author={King, JS and Kubiske, ME and Pregitzer, KS and Hendrey, GR and McDonald, EP and Giardina, CP and Quinn, VS and Karnosky, DF}, year={2005}, month={Dec}, pages={623–635} }
 @article{loranger_pregitzer_king_2004, title={Elevated CO2 and O3t concentrations differentially affect selected groups of the fauna in temperate forest soils}, volume={36}, ISSN={0038-0717}, url={http://dx.doi.org/10.1016/j.soilbio.2004.04.022}, DOI={10.1016/j.soilbio.2004.04.022}, abstractNote={Rising atmospheric CO2 concentrations may change soil fauna abundance. How increase of tropospheric ozone (O3t) concentration will modify these responses is still unknown. We have assessed independent and interactive effects of elevated [CO2] and [O3t] on selected groups of soil fauna. The experimental design is a factorial arrangement of elevated [CO2] and [O3t] treatments, applied using Free-Air CO2 Enrichment technology to 30 m diameter rings, with all treatments replicated three times. Within each ring, three communities were established consisting of: (1) trembling aspen (Populus tremuloides) and paper birch (Betula papyrifera) (2) trembling aspen and sugar maple (Acer saccharum) and (3) trembling aspen. After 4 yr of stand development, soil fauna were extracted in each ring. Compared to the control, abundance of total soil fauna, Collembola and Acari decreased significantly under elevated [CO2] (−69, −79 and −70%, respectively). Abundance of Acari decreased significantly under elevated [O3t] (−47%). Soil fauna abundance was similar to the control under the combination of elevated [CO2+O3t]. The individual negative effects of elevated [CO2] and elevated [O3t] are negated upon exposure to both gases. We conclude that soil fauna communities will change under elevated [CO2] and elevated [O3t] in ways that cannot be predicted or explained from the exposure of ecosystems to each gas individually.}, number={9}, journal={Soil Biology and Biochemistry}, publisher={Elsevier BV}, author={Loranger, Gladys I and Pregitzer, Kurt S and King, John S}, year={2004}, month={Sep}, pages={1521–1524} }
 @misc{karnosky_zak_pregitzer_awmack_bockheim_dickson_hendrey_host_king_kopper_et al._2003, title={Tropospheric O-3 moderates responses of temperate hardwood forests to elevated CO2: a synthesis of molecular to ecosystem results from the Aspen FACE project}, volume={17}, ISSN={["1365-2435"]}, DOI={10.1046/j.1365-2435.2003.00733.x}, abstractNote={Summary}, number={3}, journal={FUNCTIONAL ECOLOGY}, author={Karnosky, DF and Zak, DR and Pregitzer, KS and Awmack, CS and Bockheim, JG and Dickson, RE and Hendrey, GR and Host, GE and King, JS and Kopper, BJ and et al.}, year={2003}, month={Jun}, pages={289–304} }