@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{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{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{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{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{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{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{wu_guan_hayek_restrepo-coupe_wiedemann_xu_wehr_christoffersen_miao_silva_et al._2017, title={Partitioning controls on Amazon forest photosynthesis between environmental and biotic factors at hourly to interannual timescales}, volume={23}, ISSN={["1365-2486"]}, DOI={10.1111/gcb.13509}, abstractNote={Abstract}, number={3}, journal={GLOBAL CHANGE BIOLOGY}, author={Wu, Jin and Guan, Kaiyu and Hayek, Matthew and Restrepo-Coupe, Natalia and Wiedemann, Kenia T. and Xu, Xiangtao and Wehr, Richard and Christoffersen, Bradley O. and Miao, Guofang and Silva, Rodrigo and et al.}, year={2017}, month={Mar}, pages={1240–1257} }
 @article{liu_wang_lajeunesse_miao_piao_wan_wu_wang_yang_li_et al._2016, title={A cross-biome synthesis of soil respiration and its determinants under simulated precipitation changes}, volume={22}, ISSN={["1365-2486"]}, DOI={10.1111/gcb.13156}, abstractNote={Abstract}, number={4}, journal={GLOBAL CHANGE BIOLOGY}, author={Liu, Lingli and Wang, Xin and Lajeunesse, Marc J. and Miao, Guofang and Piao, Shilong and Wan, Shiqiang and Wu, Yuxin and Wang, Zhenhua and Yang, Sen and Li, Ping and et al.}, year={2016}, month={Apr}, pages={1394–1405} }
 @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} }
 @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{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} }