@article{aguilos_sun_liu_zhang_starr_oishi_thomas l. o'halloran_forsythe_wang_zhu_et al._2024, title={Energy availability and leaf area dominate control of ecosystem evapotranspiration in the southeastern U.S (vol 349, 109960, 2024)}, volume={350}, ISSN={["1873-2240"]}, DOI={10.1016/j.agrformet.2024.109986}, journal={AGRICULTURAL AND FOREST METEOROLOGY}, author={Aguilos, Maricar and Sun, Ge and Liu, Ning and Zhang, Yulong and Starr, Gregory and Oishi, Andrew Christopher and Thomas L. O'Halloran and Forsythe, Jeremy and Wang, Jingfeng and Zhu, Modi and et al.}, year={2024}, month={May} }
 @article{mitra_minick_gavazzi_prajapati_aguilos_miao_domec_mcnulty_sun_king_et al._2024, title={Toward spectrally truthful models for gap-filling soil respiration and methane fluxes. A case study in coastal forested wetlands in North Carolina}, volume={353}, ISSN={["1873-2240"]}, url={https://doi.org/10.1016/j.agrformet.2024.110038}, DOI={10.1016/j.agrformet.2024.110038}, abstractNote={Soil respiration (Rs) and methane (FCH4) fluxes are two important metrics of ecosystem metabolism. An accurate estimate of the budget of these two greenhouse gases is critical to understanding their response to climate and land-use changes. Reconstructing continuous time series of gappy chamber Rs and eddy-covariance derived FCH4 measurements is usually done based on correlative relationships of these fluxes with environmental variables. However, current approaches do not account for the fact that different environmental drivers affect the carbon fluxes at different temporal scales. Here we propose a novel gapfilling technique that accounts for the specific spectral frequencies at which each of the environmental variables covaries with Rs and FCH4 - photosynthetically active radiation at diel scale, soil temperature at synoptic scale, and soil moisture, water table depth and atmospheric pressure at synoptic and seasonal scale. The method was applied on two operational loblolly pine plantations of different ages and a mixed hardwood forested wetland on the lower coastal plain of North Carolina. The time series of these environmental drivers were reconstructed using wavelet decomposition and a Daubechies wavelet filter. Further, to consider the joint influence of the environmental drivers, parametric (elastic net regression, support vector machine, gradient boost and artificial neural network), and nonparametric (Bayesian) statistical models were chosen, and compared the results with Q10 and Marginal Distribution Sampling (MDS) outputs. In all cases, the algorithms were trained on 70 % of the data and validated with the remaining data. Spectral-filtered models did not significantly differ from those driven by unfiltered data with respect to Rs and FCH4 predictions. While all the spectrally driven algorithms achieved high predictive accuracy against Q10, the increase in model fit compared to MDS was minimal. Spectral data filtering modestly improves model accuracy, shedding light on complex environmental and biological factors affecting greenhouse gas flux variability.}, journal={AGRICULTURAL AND FOREST METEOROLOGY}, author={Mitra, Bhaskar and Minick, Kevan and Gavazzi, Michael and Prajapati, Prajaya and Aguilos, Maricar and Miao, Guofang and Domec, Jean-Christophe and Mcnulty, Steve G. and Sun, Ge and King, John S. and et al.}, year={2024}, month={Jun} }
 @article{crockett_atkins_guo_sun_potter_ollinger_silva_tang_woodall_holgerson_et al._2023, title={Structural and species diversity explain aboveground carbon storage in forests across the United States: Evidence from GEDI and forest inventory data}, volume={295}, ISSN={["1879-0704"]}, DOI={10.1016/j.rse.2023.113703}, abstractNote={Since biodiversity often increases ecosystem functioning, changes in tree species diversity could substantially influence terrestrial carbon cycling. Yet much less is known about the relationships between forest structural diversity (i.e., the number and physical arrangement of vegetation elements in a forest) and carbon cycling, and the factors that mediate these relationships. We capitalize on spaceborne lidar data from NASA's Global Ecosystem Dynamics Investigation (GEDI) and on-the-ground forest inventory and analysis (FIA) data from 1796 plots across the contiguous United States to assess relationships among the structural and species diversity of live trees and aboveground carbon storage. We found that carbon storage was more strongly correlated with structural diversity than with species diversity, for both forest inventory-based metrics of structural diversity (e.g., height and DBH diversity) and GEDI-based canopy metrics (i.e., foliage height diversity (FHD)). However, the strength of diversity‑carbon storage relationships was mediated by forest origin and forest types. For both plot-based and GEDI-based metrics, the relationship between structural diversity (i.e., height diversity, DBH diversity, and FHD) and carbon storage was positive in natural forests for all forest types (broadleaf, mixed, conifer). For planted forests, structural diversity showed positive relationships in planted conifer forests but not in planted mixed forests. Species diversity did not show strong associations with carbon storage in natural forests but showed a positive relationship in mixed coniferous-broadleaf planted forests. Although plot-based structural diversity metrics refine our understanding of drivers of forest carbon balances at the plot scale, remotely sensed metrics such as those from GEDI can help extend that understanding to regional/national scales in a spatially continuous manner. Carbon storage showed stronger associations with plot-based structural diversity than with stand age, soil variables, or climate variables. Incorporating structural diversity into management and restoration strategies could help guide efforts to increase carbon storage and mitigate climate change as nature-based solutions.}, journal={REMOTE SENSING OF ENVIRONMENT}, author={Crockett, Erin T. H. and Atkins, Jeff W. and Guo, Qinfeng and Sun, Ge and Potter, Kevin M. and Ollinger, Scott and Silva, Carlos A. and Tang, Hao and Woodall, Christopher W. and Holgerson, Justin and et al.}, year={2023}, month={Sep} }
 @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{liu_dobbs_caldwell_miniat_sun_duan_nelson_bolstad_carlson_2022, title={Inter-Basin Transfers Extend the Benefits of Water From Forests to Population Centers Across the Conterminous US}, volume={58}, ISSN={["1944-7973"]}, DOI={10.1029/2021WR031537}, abstractNote={Abstract}, number={5}, journal={WATER RESOURCES RESEARCH}, author={Liu, Ning and Dobbs, G. Rebecca and Caldwell, Peter V. and Miniat, Chelcy Ford and Sun, Ge and Duan, Kai and Nelson, Stacy A. C. and Bolstad, Paul V. and Carlson, Christopher P.}, year={2022}, month={May} }
 @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{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{amatya_tian_marion_caldwell_laseter_youssef_grace_chescheir_panda_ouyang_et al._2021, title={Estimates of Precipitation IDF Curves and Design Discharges for Road-Crossing Drainage Structures: Case Study in Four Small Forested Watersheds in the Southeastern US}, volume={26}, ISSN={["1943-5584"]}, DOI={10.1061/(ASCE)HE.1943-5584.0002052}, abstractNote={AbstractWe compared precipitation intensity-duration-frequency (PIDF) curves developed for four small forested watersheds to spatially interpolated estimates from the National Oceanic and Atmospher...}, number={4}, journal={JOURNAL OF HYDROLOGIC ENGINEERING}, author={Amatya, D. M. and Tian, S. and Marion, D. A. and Caldwell, P. and Laseter, S. and Youssef, M. A. and Grace, J. M. and Chescheir, G. M. and Panda, S. and Ouyang, Y. and et al.}, year={2021}, month={Apr} }
 @article{liu_caldwell_dobbs_miniat_bolstad_nelson_sun_2021, title={Forested lands dominate drinking water supply in the conterminous United States}, volume={16}, ISSN={["1748-9326"]}, DOI={10.1088/1748-9326/ac09b0}, abstractNote={Abstract}, number={8}, journal={ENVIRONMENTAL RESEARCH LETTERS}, author={Liu, Ning and Caldwell, Peter V and Dobbs, G. Rebecca and Miniat, Chelcy Ford and Bolstad, Paul V and Nelson, Stacy A. C. and Sun, Ge}, year={2021}, month={Aug} }
 @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{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{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{gibson_sun_nichols_2020, title={Water balance of municipal wastewater irrigation in a coastal forested watershed}, volume={13}, ISSN={["1936-0592"]}, DOI={10.1002/eco.2227}, abstractNote={Abstract}, number={5}, journal={ECOHYDROLOGY}, author={Gibson, Nancy E. and Sun, Ge and Nichols, Elizabeth Guthrie}, year={2020}, month={Jul} }
 @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{duan_caldwell_sun_mcnulty_zhang_shuster_liu_bolstad_2019, title={Data on projections of surface water withdrawal, consumption, and availability in the conterminous United States through the 21st century}, volume={23}, ISSN={2352-3409}, url={http://dx.doi.org/10.1016/J.DIB.2019.103786}, DOI={10.1016/j.dib.2019.103786}, abstractNote={We report data on the projections of annual surface water demand and supply in the conterminous United States at a high spatial resolution from 2010s to the end of the 21st century, including: 1) water withdrawal and consumption in the water-use sectors of domestic, thermoelectric power generation, and irrigation; 2) availability of surface water generated from local watershed runoff, accumulated from upstream areas, and artificially transferred from other basins. These data were derived from the projected changes in climate, population, energy structure, technology and water uses. These data are related to the original article “Understanding the role of regional water connectivity in mitigating climate change impacts on surface water supply stress in the United States” (Duan et al., 2019) [1].}, journal={Data in Brief}, publisher={Elsevier BV}, author={Duan, Kai and Caldwell, Peter V. and Sun, Ge and McNulty, Steven G. and Zhang, Yang and Shuster, Erik and Liu, Bingjun and Bolstad, Paul V.}, year={2019}, month={Apr}, pages={103786} }
 @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{duan_caldwell_sun_mcnulty_zhang_shuster_liu_bolstad_2019, title={Understanding the role of regional water connectivity in mitigating climate change impacts on surface water supply stress in the United States}, volume={570}, ISSN={["1879-2707"]}, DOI={10.1016/j.jhydrol.2019.01.011}, abstractNote={Surface water supply for a watershed relies on local water generated from precipitation and water connections with other watersheds. These connections are confined by topography and infrastructure, and respond diversely to stressors such as climate change, population growth, increasing energy and water demands. This study presents an integrative simulation and evaluation framework that incorporates the natural and anthropogenic water connections (i.e., stream flows, inter-basin water transfers, water withdrawals and return flows) among the 2099 8-digit Hydrologic Unit Code (HUC-8) watersheds across the conterminous United States. The framework is then applied to investigate the potential impacts of changes in climate and water use on regional water availability and water stress (the ratio of demand to supply). Our projections suggest that highly water-stressed areas may expand from 14% to 18% and the stressed population would increase from 19% to 24% by 2070–2099. Climate-change mitigation practices (e.g., energy structure reform, technology innovation) could largely offset these trends by reducing demand and enhancing supply. At the watershed scale, the spatially inhomogeneous responses to future changes suggest that regional water connectivity could significantly buffer the potential stress escalations due to the redistribution of water resources and diverse changes in consumptive uses and water supplies in different source areas. However, the detrimental future changes (e.g., depleting river discharges, larger demands of water withdrawal) may aggravate conflicts over water rights among regions and challenge our current water infrastructure system. This study provides new insights into the critical role of regional water connectivity in water supply security, and highlights the increasing need for integrated monitoring and management of water resources at various spatial levels in a changing world.}, journal={JOURNAL OF HYDROLOGY}, author={Duan, Kai and Caldwell, Peter V. and Sun, Ge and McNulty, Steven G. and Zhang, Yang and Shuster, Erik and Liu, Bingjun and Bolstad, Paul V.}, year={2019}, month={Mar}, pages={80–95} }
 @article{lin_domec_ward_marshall_kin_laviner_fox_west_sun_mcnulty_et al._2019, title={Using delta C-13 and delta O-18 to analyze loblolly pine (Pinus taeda L.) response to experimental drought and fertilization}, volume={39}, ISSN={["1758-4469"]}, DOI={10.1093/treephys/tpz096}, abstractNote={Abstract}, number={12}, journal={TREE PHYSIOLOGY}, author={Lin, Wen and Domec, Jean-Christophe and Ward, Eric J. and Marshall, John and Kin, John S. and Laviner, Marshall A. and Fox, Thomas R. and West, Jason B. and Sun, Ge and McNulty, Steve and et al.}, year={2019}, month={Dec}, pages={1984–1994} }
 @book{hallema_sun_caldwell_robinne_bladon_norman_liu_cohen_mcnulty_2019, title={Wildland fire impacts on water yield across the contiguous United States}, url={http://dx.doi.org/10.2737/srs-gtr-238}, DOI={10.2737/srs-gtr-238}, abstractNote={Wildland fires in the contiguous United States (CONUS) have increased in size and severity, but much remains unclear about the impact of fire size and burn severity on water supplies used for drinking, irrigation, industry, and hydropower. While some have investigated large-scale fire patterns, long-term effects on runoff, and the simultaneous effect of fire and climate trends on surface water yield, no studies account for all these factors and their interactions at the same time. In this report, we present critical new information for the National Cohesive Wildland Fire Management Strategy—a first-time CONUS-wide assessment of observed and potential wildland fire impacts on surface water yield. First, we analyzed data from 168 fire-affected locations, collected between 1984 and 2013, with machine learning and used climate elasticity models to correct for the local climate baseline impact. Stream gage data show that annual river flow increased most in the Lower Mississippi and Lower and Upper Colorado water resource regions, however they do not show which portion of this increase is caused by fire and which portion results from local climate trends. Our machine learning model identified local climate trends as the main driver of water yield change and determined wildland fires must affect at least 19 percent of a watershed >10 km2 to change its annual water yield. A closer look at 32 locations with fires covering at least 19 percent of a watershed >10 km2 revealed that wildfire generally enhanced annual river flow. Fires increased river flow relatively the most in the Lower Colorado, Pacific Northwest, and California regions. In the Lower Colorado and Pacific Northwest regions, flow increased despite post-fire drought conditions. In southern California, post-fire drought effects masked the flow enhancement attributed to wildfire, meaning that annual water yield declined but not as much as expected based on the decline in precipitation. Prescribed burns in the Southeastern United States did not produce a widespread effect on river flow, because the area affected was typically too small and characterized by only low burn severity. In the second stage of the assessment, we performed full-coverage simulations of the CONUS with the Water Supply Stress Index (WaSSI) hydrologic model (88,000 HUC-12-level watersheds) for the period between 2001 and 2010. This enables us to fill in the gaps of areas with scarce data and to identify regions with large potential increases in post-fire annual water yield (+10 to +50 percent): midto high-elevation forests in northeastern Washington, northwestern Montana, central Minnesota, southern Utah, Colorado, and South Dakota, and coastal forests in Georgia and northern Florida. A hypothetical 20-percent forest burn impact scenario for the CONUS suggests that surface yield can increase up to +10 percent in most watersheds, and even more in some watersheds depending on climate, soils, and vegetation. The insights gained from this quantitative analysis have major implications for flood mitigation and watershed restoration, and are vital to forest management policies aimed at reducing fire impact risk and improving water supply under a changing climate.}, institution={U.S. Department of Agriculture, Forest Service, Southern Research Station}, author={Hallema, Dennis and Sun, Ge and Caldwell, Peter and Robinne, Francois-Nicolas and Bladon, Kevin D. and Norman, Steve and Liu, Yongqiang and Cohen, Erika C. and McNulty, Steve}, year={2019} }
 @article{panda_amatya_jackson_sun_noormets_2018, title={Automated Geospatial Models of Varying Complexities for Pine Forest Evapotranspiration Estimation with Advanced Data Mining}, volume={10}, ISSN={["2073-4441"]}, DOI={10.3390/w10111687}, abstractNote={The study goal was to develop automated user-friendly remote-sensing based evapotranspiration (ET) estimation tools: (i) artificial neural network (ANN) based models, (ii) ArcGIS-based automated geospatial model, and (iii) executable software to predict pine forest daily ET flux on a pixel- or plot average-scale. Study site has had long-term eddy-flux towers for ET measurements since 2006. Cloud-free Landsat images of 2006−2014 were processed using advanced data mining to obtain Principal Component bands to correlate with ET data. The regression model’s r2 was 0.58. The backpropagation neural network (BPNN) and radial basis function network (RBFN) models provided a testing/validation average absolute error of 0.18 and 0.15 Wm−2 and average accuracy of 81% and 85%, respectively. ANN models though robust, require special ANN software and skill to operate; therefore, automated geospatial model (toolbox) was developed on ArcGIS ModelBuilder as user-friendly alternative. ET flux map developed with model tool provided consistent ET patterns for landuses. The software was developed for lay-users for ET estimation.}, number={11}, journal={WATER}, author={Panda, Sudhanshu and Amatya, Devendra M. and Jackson, Rhett and Sun, Ge and Noormets, Asko}, year={2018}, month={Nov} }
 @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{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{sun_alstad_chen_chen_ford_lin_liu_lu_mcnulty_miao_et al._2011, title={A general predictive model for estimating monthly ecosystem evapotranspiration}, volume={4}, ISSN={["1936-0592"]}, DOI={10.1002/eco.194}, abstractNote={Abstract}, number={2}, journal={ECOHYDROLOGY}, author={Sun, Ge and Alstad, Karrin and Chen, Jiquan and Chen, Shiping and Ford, Chelcy R. and Lin, Guanghui and Liu, Chenfeng and Lu, Nan and McNulty, Steven G. and Miao, Haixia and et al.}, year={2011}, month={Mar}, pages={245–255} }
 @article{sun_caldwell_noormets_mcnulty_cohen_myers_domec_treasure_mu_xiao_et al._2011, title={Upscaling key ecosystem functions across the conterminous United States by a water-centric ecosystem model}, volume={116}, ISSN={["2169-8961"]}, DOI={10.1029/2010jg001573}, abstractNote={[1] We developed a water-centric monthly scale simulation model (WaSSI-C) by integrating empirical water and carbon flux measurements from the FLUXNET network and an existing water supply and demand accounting model (WaSSI). The WaSSI-C model was evaluated with basin-scale evapotranspiration (ET), gross ecosystem productivity (GEP), and net ecosystem exchange (NEE) estimates by multiple independent methods across 2103 eight-digit Hydrologic Unit Code watersheds in the conterminous United States from 2001 to 2006. Our results indicate that WaSSI-C captured the spatial and temporal variability and the effects of large droughts on key ecosystem fluxes. Our modeled mean (±standard deviation in space) ET (556 ± 228 mm yr−1) compared well to Moderate Resolution Imaging Spectroradiometer (MODIS) based (527 ± 251 mm yr−1) and watershed water balance based ET (571 ± 242 mm yr−1). Our mean annual GEP estimates (1362 ± 688 g C m−2 yr−1) compared well (R2 = 0.83) to estimates (1194 ± 649 g C m−2 yr−1) by eddy flux-based EC-MOD model, but both methods led significantly higher (25–30%) values than the standard MODIS product (904 ± 467 g C m−2 yr−1). Among the 18 water resource regions, the southeast ranked the highest in terms of its water yield and carbon sequestration capacity. When all ecosystems were considered, the mean NEE (−353 ± 298 g C m−2 yr−1) predicted by this study was 60% higher than EC-MOD's estimate (−220 ± 225 g C m−2 yr−1) in absolute magnitude, suggesting overall high uncertainty in quantifying NEE at a large scale. Our water-centric model offers a new tool for examining the trade-offs between regional water and carbon resources under a changing environment.}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES}, author={Sun, Ge and Caldwell, Peter and Noormets, Asko and McNulty, Steven G. and Cohen, Erika and Myers, Jennifer Moore and Domec, Jean-Christophe and Treasure, Emrys and Mu, Qiaozhen and Xiao, Jingfeng and et al.}, year={2011}, month={May} }
 @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_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{sun_noormets_chen_mcnulty_2008, title={Evapotranspiration estimates from eddy covariance towers and hydrologic modeling in managed forests in Northern Wisconsin, USA}, volume={148}, ISSN={["0168-1923"]}, DOI={10.1016/j.agrformet.2007.08.010}, abstractNote={Direct measurement of ecosystem evapotranspiration by the eddy covariance method and simulation modeling were employed to quantify the growing season (May–October) evapotranspiration (ET) of eight forest ecosystems representing a management gradient in dominant forest types and age classes in the Upper Great Lakes Region from 2002 to 2003. We measured net exchange of water vapor fluxes in a 63-year-old mature hardwood (MHW) stand, a 60-year-old mature red pine (MRP) stand, a 3-year-old young hardwood (YHW) stand, a 17-year-old intermediate hardwood (IHW) stand, a young red pine (YRP age 8) stand, an intermediate red pine (IRP age 21) stand, and two pine barren ecosystems burned 12 years (PB1) and 2 years (PB2) ago. Field data suggested that there were no significant differences in growing season (June–September) ET/precipitation ratio among all ecosystems in 2002. However, PB2 had significantly lower ET/precipitation than those of other ecosystems in 2003. The ratios were much higher for all ecosystems, up to 0.90 for IHW, during the peak summer months (June–July). PB2 was the lowest (0.64) during that period. Stand leaf area index alone did not explain ecosystem ET at the landscape scale. Seasonal ET values measured by the eddy covariance method were significantly lower than those simulated with a process-based hydrologic model, MIKE SHE. Our integration approach combined with field measurements and simulation modeling proved to be useful in providing a full picture of the effects of forest cover type change on landscape scale water balance at multiple temporal scales. The ET procedure used in the MIKE SHE model needs improvement to fully account for the effects of vapor pressure deficit on tree transpiration. Seasonal distributions of ET coincided with precipitation in the growing season, when fluxes estimated by both field and models were the highest. The simulation model suggests that removal of conifer forests in the study region may reduce ET immediately by 113–30 mm/year or about 20%, but our field data suggests that ET can recover within 8–25 years from re-growth of hardwood forests.}, number={2}, journal={AGRICULTURAL AND FOREST METEOROLOGY}, author={Sun, G. and Noormets, A. and Chen, J. and McNulty, S. G.}, year={2008}, month={Feb}, pages={257–267} }
 @article{deforest_noormets_mcnulty_sun_tenney_chen_2006, title={Phenophases alter the soil respiration-temperature relationship in an oak-dominated forest}, volume={51}, ISSN={["1432-1254"]}, DOI={10.1007/s00484-006-0046-7}, abstractNote={Soil respiration (SR) represents a major component of forest ecosystem respiration and is influenced seasonally by environmental factors such as temperature, soil moisture, root respiration, and litter fall. Changes in these environmental factors correspond with shifts in plant phenology. In this study, we examined the relationship between canopy phenophases (pre-growth, growth, pre-dormancy, and dormancy) and SR sensitivity to changes in soil temperature (T(S)). SR was measured 53 times over 550 days within an oak forest in northwest Ohio, USA. Annual estimates of SR were calculated with a Q(10) model based on T(S) on a phenological (PT), or annual timescale (AT), or T(S) and soil volumetric water content (VWC) on a phenological (PTM) or annual (ATM) timescale. We found significant (p<0.01) difference in apparent Q(10) from year 2004 (1.23) and year 2005 (2.76) during the growth phenophase. Accounting for moisture-sensitivity increased model performance compared to temperature-only models: the error was -17% for the ATM model and -6% for the PTM model. The annual models consistently underestimated SR in summer and overestimated it in winter. These biases were reduced by delineating SR by tree phenophases and accounting for variation in soil moisture. Even though the bias of annual models in winter SR was small in absolute scale, the relative error was about 91%, and may thus have significant implications for regional and continental C balance estimates.}, number={2}, journal={INTERNATIONAL JOURNAL OF BIOMETEOROLOGY}, author={DeForest, Jared L. and Noormets, Asko and McNulty, Steve G. and Sun, Ge and Tenney, Gwen and Chen, Jiquan}, year={2006}, month={Nov}, pages={135–144} }
 @inbook{noormets_ewers_sun_mackay_zheng_mcnulty_chen_2006, title={Water and carbon cycles in heterogeneous landscapes: an ecosystem perspective}, ISBN={1600210473}, booktitle={Ecology of Hierarchical Landscapes: From Theory to Application}, publisher={Carbondale, IL: Nova Publishing}, author={Noormets, A. and Ewers, B. and Sun, G. and Mackay, S. and Zheng, D. and McNulty, S. and Chen, J.}, editor={J. Chen, S. C. Saunders and K. D. Brosofske and Crow, T. R.Editors}, year={2006}, pages={89–123} }
 @article{cui_li_sun_trettin_2005, title={Linkage of MIKE SHE to Wetland-DNDC for carbon budgeting and anaerobic biogeochemistry simulation}, volume={72}, ISSN={["1573-515X"]}, DOI={10.1007/s10533-004-0367-8}, number={2}, journal={BIOGEOCHEMISTRY}, author={Cui, JB and Li, CS and Sun, G and Trettin, C}, year={2005}, month={Feb}, pages={147–167} }
 @article{lu_sun_mcnulty_amatya_2003, title={Modeling actual evapotranspiration from forested watersheds across the Southeastern United States}, volume={39}, DOI={10.1111/j.1752-1688.2003.tb04413.x}, abstractNote={ABSTRACT:  About 50 to 80 percent of precipitation in the southeastern United States returns to the atmosphere by evapotranspiration. As evapotranspiration is a major component in the forest water balances, accurately quantifying it is critical to predicting the effects of forest management and global change on water, sediment, and nutrient yield from forested watersheds. However, direct measurement of forest evapotranspiration on a large basin or a regional scale is not possible. The objectives of this study were to develop an empirical model to estimate long‐term annual actual evapotranspiration (ART) for forested watersheds and to quantify spatial AET patterns across the southeast. A geographic information system (GIS) database including land cover, daily streamflow, and climate was developed using long term experimental and monitoring data from 39 forested watersheds across the region. Using the stepwise selection method implemented in a statistical modeling package, a long term annual AET model was constructed. The final multivariate linear model includes four independent variables—annual precipitation, watershed latitude, watershed elevation, and percentage of forest coverage. The model has an adjusted R2 of 0.794 and is sufficient to predict long term annual ART for forested watersheds across the southeastern United States. The model developed by this study may be used to examine the spatial variability of water availability, estimate annual water loss from mesoscale watersheds, and project potential water yield change due to forest cover change.}, number={4}, journal={Journal of the American Water Resources Association}, author={Lu, J. B. and Sun, G. and McNulty, S. G. and Amatya, D. M.}, year={2003}, pages={887–896} }
 @article{sun_mcnulty_amatya_skaggs_swift_shepard_riekerk_2002, title={A comparison of the watershed hydrology of coastal forested wetlands and the mountainous uplands in the Southern US}, volume={263}, ISSN={["0022-1694"]}, DOI={10.1016/S0022-1694(02)00064-1}, abstractNote={Hydrology plays a critical role in wetland development and ecosystem structure and functions. Hydrologic responses to forest management and climate change are diverse in the Southern United States due to topographic and climatic differences. This paper presents a comparison study on long-term hydrologic characteristics (long-term seasonal runoff patterns, water balances, storm flow patterns) of three watersheds in the southern US. These three watersheds represent three types of forest ecosystems commonly found in the lower Atlantic coastal plain and the Appalachian upland mountains. Compared to the warm, flat, and shallow groundwater dominated pine flatwoods on the coast, the inland upland watershed was found to have significantly higher water yield, Precipitation/Hamon's potential evapotranspiration ratio (1.9 for upland vs 1.4 and 0.9 for wetlands), and runoff/precipitation ratio (0.53±0.092 for upland vs 0.30±0.079 and 0.13±0.094 for wetlands). Streamflow from flatwoods watersheds generally are discontinuous most of the years while the upland watershed showed continuous flows in most years. Stormflow peaks in a cypress–pine flatwoods system were smaller than that in the upland watershed for most cases, but exceptions occurred under extreme wet conditions. Our study concludes that climate is the most important factor in determining the watershed water balances in the southern US. Topography effects streamflow patterns and stormflow peaks and volume, and is the key to wetland development in the southern US.}, number={1-4}, journal={JOURNAL OF HYDROLOGY}, author={Sun, G and McNulty, SG and Amatya, DM and Skaggs, RW and Swift, LW and Shepard, JP and Riekerk, H}, year={2002}, month={Jun}, pages={92–104} }
 @article{zhang_li_trettin_li_sun_2002, title={An integrated model of soil, hydrology, and vegetation for carbon dynamics in wetland ecosystems}, volume={16}, ISSN={["0886-6236"]}, DOI={10.1029/2001gb001838}, abstractNote={Wetland ecosystems are an important component in global carbon (C) cycles and may exert a large influence on global climate change. Predictions of C dynamics require us to consider interactions among many critical factors of soil, hydrology, and vegetation. However, few such integrated C models exist for wetland ecosystems. In this paper, we report a simulation model, Wetland‐DNDC, for C dynamics and methane (CH4) emissions in wetland ecosystems. The general structure of Wetland‐DNDC was adopted from PnET‐N‐DNDC, a process‐oriented biogeochemical model that simulates C and N dynamics in upland forest ecosystems. Several new functions and algorithms were developed for Wetland‐DNDC to capture the unique features of wetland ecosystems, such as water table dynamics, growth of mosses and herbaceous plants, and soil biogeochemical processes under anaerobic conditions. The model has been validated against various observations from three wetland sites in Northern America. The validation results are in agreement with the measurements of water table dynamics, soil temperature, CH4 fluxes, net ecosystem productivity (NEP), and annual C budgets. Sensitivity analysis indicates that the most critical input factors for C dynamics in the wetland ecosystems are air temperature, water outflow parameters, initial soil C content, and plant photosynthesis capacity. NEP and CH4 emissions are sensitive to many of the tested input variables. By integrating the primary drivers of climate, hydrology, soil and vegetation, the Wetland‐DNDC model is capable of predicting C biogeochemical cycles in wetland ecosystems.}, number={4}, journal={GLOBAL BIOGEOCHEMICAL CYCLES}, author={Zhang, Y and Li, CS and Trettin, CC and Li, H and Sun, G}, year={2002} }
 @article{sun_mcnulty_shepard_amatya_riekerk_comerford_skaggs_swift_2001, title={Effects of timber management on the hydrology of wetland forests in the southern United States}, volume={143}, ISSN={["0378-1127"]}, DOI={10.1016/s0378-1127(00)00520-x}, abstractNote={The objectives of this paper are to review the hydrologic impacts of various common forest management practices that include harvesting, site preparation, and drainage. Field hydrological data collected during the past 5–10 years from ten forested wetland sites across the southern US are synthesized using various methods including hydrologic simulation models and Geographic Information Systems. Wetland systems evaluated include red river bottoms, black river bottoms, pocosins, wet mineral flats, cypress domes, and pine flatwoods. Hydrologic variables used in this assessment include water table level, drainage, and storm flow on different spatial and temporal scales. Wetland ecosystems have higher water storage capacity and higher evapotranspiration than uplands. Hydrologic impacts of forest management are variable, but generally minor, especially when forest best management practices are adopted. A conceptually generalized model is developed to illustrate the relative magnitude of hydrologic effects of forest management on different types of wetlands in the southern US. This model suggests that in addition to soils, wetland types, and management practice options, climate is an important factor in controlling wetland hydrology and the magnitude of disturbance impacts. Bottomland wetlands, partial harvesting, and warm climate usually offer conditions that result in low hydrologic impact.}, number={1-3}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Sun, G and McNulty, SG and Shepard, JP and Amatya, DM and Riekerk, H and Comerford, NB and Skaggs, W and Swift, L}, year={2001}, month={Apr}, pages={227–236} }
 @article{sun_amatya_mcnulty_skaggs_hughes_2000, title={Climate change impacts on the hydrology and productivity of a pine plantation}, volume={36}, ISSN={["1752-1688"]}, DOI={10.1111/j.1752-1688.2000.tb04274.x}, abstractNote={ABSTRACT:  There are increasing concerns in the forestry community about global climate change and variability associated with elevated atmospheric CO2. Changes in precipitation and increases in air temperature could impose additional stress on forests during the next century. For a study site in Carteret County, North Carolina, the General Circulation Model, HADCM2, predicts that by the year 2099, maximum air temperature will increase 1.6 to 1.9°C, minimum temperature will increase 2.5 to 2.8°C, and precipitation will increase 0 to 10 percent compared to the mid‐1990s. These changes vary from season to season. We utilized a forest ecosystem process model, PnET‐II, for studying the potential effects of climate change on drainage outflow, evapotranspiration, leaf area index (LAI) and forest Net Primary Productivity (NPP). This model was first validated with long term drainage and LAI data collected at a 25‐ha mature loblolly pine (Pinus taeda L.) experimental watershed located in the North Carolina lower coastal plain. The site is flat with poorly drained soils and high groundwater table. Therefore, a high field capacity of 20 cm was used in the simulation to account for the topographic effects. This modeling study suggested that future climate change would cause a significant increase of drainage (6 percent) and forest productivity (2.5 percent). Future studies should consider the biological feedback (i.e., stomata conductance and water use efficiency) to air temperature change.}, number={2}, journal={JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION}, author={Sun, G and Amatya, DM and McNulty, SG and Skaggs, RW and Hughes, JH}, year={2000}, month={Apr}, pages={367–374} }
 @article{sun_riekerk_kornhak_2000, title={Ground-water-table rise after forest harvesting on cypress-pine flatwoods in Florida}, volume={20}, ISSN={["0277-5212"]}, DOI={10.1672/0277-5212(2000)020[0101:gwtraf]2.0.co;2}, abstractNote={Forest removal represents one of the large-scale ecosystem disturbances that concern water quality degradation, species composition change, and wildlife habitat alteration along the Florida coast. We conducted a five-year study with the objective to address effects of two forest management scenarios on the water regimes of cypress-pine flatwoods ecosystems in the lower coastal plain. Three experimental blocks (16–21 ha) were used in this study, with one representing control (C), one wetlands-harvest-only (W), and one wetlands+uplands harvest (ALL). Within the center of each block, a representative cypress wetland and its surrounding pine upland were extensively instrumented to quantify the changes of each hydrologic variable induced by tree removal. Water levels in cypress wetlands in both treatment areas were significantly elevated about 32–41 cm on average, and outflow doubled in the five-month dry period immediately following the tree harvesting. The ground-water table in the upland was also raised by about 29 cm on average due to ALL, but it was not affected significantly during the entire post-treatment period by W. During wet periods, the treatment effects for both wetlands and uplands were not significant. Causes for spatial and temporal variability of hydrologic responses to forest harvesting are speculated to be 1) total evapotranspiration does not change significantly in flatwoods after tree removal during wet seasons; 2) specific yield of the flatwoods soils is variable in time and space; and 3) lateral water movement from uplands to wetlands. From this study, we conclude that harvesting both uplands and wetlands causes greater response than harvesting wetlands only. The impacts lasted for more than two years but were most pronounced only in the dry periods. Temporal and spatial variations of each hydrologic component should be considered in evaluating the hydrologic impact of forest management on the flatwoods landscape.}, number={1}, journal={WETLANDS}, author={Sun, G and Riekerk, H and Kornhak, LV}, year={2000}, month={Mar}, pages={101–112} }
 @inproceedings{sun_lu_gartner_miwa_trettin_2000, title={Water budgets of two forests watersheds in South Carolina}, booktitle={Water quantity and quality issues in coastal urban areas: Proceedings, American Water Resources Association's Annual Water Resources Conference, November 6-9, 2000, Miami Florida}, author={Sun, G. and Lu, J. and Gartner, D. and Miwa, M. and Trettin, C. C.}, year={2000}, pages={199–202} }
 @inproceedings{sun_amatya_mcnulty_skaggs_hughes_1999, title={Potential impact of climate change on the hydrology and productivity of a drained loblolly pine plantation in North Carolina}, booktitle={Proceedings: Specialty Conference on Potential Consequences of Climate Variability and Change to Water Resources of the United States: May 10-12, 1999, Atlanta, Georgia  (American Water Resources Association technical publication series ; TPS-99-1).}, publisher={Herndon, VA: American Water Resources Association}, author={Sun, G. and Amatya, D. M. and McNulty, S. G. and Skaggs, R. W. and Hughes, J. H.}, year={1999}, pages={403–408} }
 @inproceedings{sun_mcnulty_1998, title={Modeling soil erosion and transport on forest landscape}, booktitle={Proceedings of conference 29: February 16-20, 1998, Reno, Nevada, USA}, publisher={Steamboat Springs, CO: International Erosion Control Association}, author={Sun, G. and McNulty, S.G.}, year={1998}, pages={187–198} }
 @article{sun_riekerk_comerford_1998, title={Modeling the forest hydrology of wetland-upland ecosystems in Florida}, volume={34}, ISSN={["1752-1688"]}, DOI={10.1111/j.1752-1688.1998.tb01519.x}, abstractNote={ABSTRACT:  Few hydrological models are applicable to pine flat‐woods which are a mosaic of pine plantations and cypress swamps. Unique features of this system include ephemeral sheet flow, shallow dynamic ground water table, high rainfall and evapotranspiration, and high infiltration rates. A FLATWOODS model has been developed specifically for the cypress wetland‐pine upland landscape by integrating a 2‐D ground water model, a Variable‐Source‐Area (VAS)‐based surface flow model, an evapotranspiration (ET) model, and an unsaturated water flow model. The FLATWOODS model utilizes a distributed approach by dividing the entire simulation domain into regular cells. It has the capability to continuously simulate the daily values of ground water table depth, ET, and soil moisture content distributions in a watershed. The model has been calibrated and validated with a 15‐year runoff and a four‐year ground water table data set from two different pine flat woods research watersheds in northern Florida. This model may be used for predicting hydrologic impacts of different forest management practices in the coastal regions.}, number={4}, journal={JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION}, author={Sun, G and Riekerk, H and Comerford, NB}, year={1998}, month={Aug}, pages={827–841} }
 @article{sun_riekerk_comerford_1998, title={Modeling the hydrologic impacts of forest harvesting on Florida flatwoods}, volume={34}, ISSN={["1093-474X"]}, DOI={10.1111/j.1752-1688.1998.tb01520.x}, abstractNote={ABSTRACT:  The great temporal and spatial variability of pine flat‐woods hydrology suggests traditional short‐term field methods may not be effective in evaluating the hydrologic effects of forest management. The FLATWOODS model was developed, calibrated and validated specifically for the cypress wetland‐pine upland landscape. The model was applied to two typical flatwoods sites in north central Florida. Three harvesting treatments (Wetland Harvesting, Wetland + Upland Harvesting, and Control) under three typical climatic conditions (dry, wet, and normal precipitation years) were simulated to study the potential first‐year effects of common forest harvesting activities on flatwoods. Long‐term (15 years) simulation was conducted to evaluate the hydrologic impacts at different stages of stand rotation. This simulation study concludes that forest harvesting has substantial effects on hydrology during dry periods and clear cutting of both wetlands and uplands has greater influence on the water regimes than partial harvesting. Compared to hilly regions, forest harvesting in the Florida coastal plains has less impact on water yield.}, number={4}, journal={JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION}, author={Sun, G and Riekerk, H and Comerford, NB}, year={1998}, month={Aug}, pages={843–854} }
 @inproceedings{mcnulty_sun_1998, title={The development and use of best practices in forest watersheds using GIS and simulation models}, number={1998}, booktitle={Proceedings of the International Symposium on Comprehensive Watershed Management (ISWM'98): 1998 Sept. 7-10 / International Research and Training Centre on Erosion and Sedimentation}, publisher={Beijing, China: China Ocean Press}, author={McNulty, S.G. and Sun, G.}, year={1998}, pages={391–398} }