@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{liu_sun_mcnulty_noormets_fang_2017, title={Environmental controls on seasonal ecosystem evapotranspiration/potential evapotranspiration ratio as determined by the global eddy flux measurements}, volume={21}, ISSN={["1607-7938"]}, DOI={10.5194/hess-21-311-2017}, abstractNote={Abstract. The evapotranspiration / potential evapotranspiration (AET / PET) ratio is traditionally termed as the crop coefficient (Kc) and has been generally used as ecosystem evaporative stress index. In the current hydrology literature, Kc has been widely used as a parameter to estimate crop water demand by water managers but has not been well examined for other types of ecosystems such as forests and other perennial vegetation. Understanding the seasonal dynamics of this variable for all ecosystems is important for projecting the ecohydrological responses to climate change and accurately quantifying water use at watershed to global scales. This study aimed at deriving monthly Kc for multiple vegetation cover types and understanding its environmental controls by analyzing the accumulated global eddy flux (FLUXNET) data. We examined monthly Kc data for seven vegetation covers, including open shrubland (OS), cropland (CRO), grassland (GRA), deciduous broad leaf forest (DBF), evergreen needle leaf forest (ENF), evergreen broad leaf forest (EBF), and mixed forest (MF), across 81 sites. We found that, except for evergreen forests (EBF and ENF), Kc values had large seasonal variation across all land covers. The spatial variability of Kc was well explained by latitude, suggesting site factors are a major control on Kc. Seasonally, Kc increased significantly with precipitation in the summer months, except in EBF. Moreover, leaf area index (LAI) significantly influenced monthly Kc in all land covers, except in EBF. During the peak growing season, forests had the highest Kc values, while croplands (CRO) had the lowest. We developed a series of multivariate linear monthly regression models for Kc by land cover type and season using LAI, site latitude, and monthly precipitation as independent variables. The Kc models are useful for understanding water stress in different ecosystems under climate change and variability as well as for estimating seasonal ET for large areas with mixed land covers.
                    }, number={1}, journal={HYDROLOGY AND EARTH SYSTEM SCIENCES}, author={Liu, Chunwei and Sun, Ge and McNulty, Steven G. and Noormets, Asko and Fang, Yuan}, year={2017}, month={Jan}, pages={311–322} }
 @article{fang_sun_caldwell_mcnulty_noormets_domec_king_zhang_zhang_lin_et al._2016, title={Monthly land cover-specific evapotranspiration models derived from global eddy flux measurements and remote sensing data}, volume={9}, ISSN={["1936-0592"]}, DOI={10.1002/eco.1629}, abstractNote={Abstract}, number={2}, journal={ECOHYDROLOGY}, author={Fang, Yuan and Sun, Ge and Caldwell, Peter and McNulty, Steven G. and Noormets, Asko and Domec, Jean-Christophe and King, John and Zhang, Zhiqiang and Zhang, Xudong and Lin, Guanghui and et al.}, year={2016}, month={Mar}, pages={248–266} }