@article{wagner_renfro_stine_ward_ange-van heugten_2023, title={Assessing Value of a Novel NC State University Two-Week Animal Science Study Abroad Course in Chiang Mai, Thailand for Post-Pandemic Student Education.}, volume={101}, ISSN={["1525-3163"]}, DOI={10.1093/jas/skad068.133}, abstractNote={
 Partially due to COVID-19 education adaptations, students and teachers alike have become more normalized to online learning platforms. While this can be valuable, it has led to an increased concern that students resist in-person meetings, lack animal and personal interactive skills and many social and cultural cues. Online platforms can allow globalized learning, but there is considerable difference between interactive study abroad education and online delivery methods. After 2 years of COVID-19 impacting study abroad programs, NC State University programs reopened in Spring 2022, although the interest and availability were understandably less than pre-pandemic years. The novel ANS 395 course Thailand: Global Animal Management Issues, Concerns and Solutions was offered Summer 2022 as a two-week, three credit hour course with 17 undergraduate students. Of these students, at least 24% had never flown, 35% had never traveled outside the USA and many more had not traveled since they were young. ANS 395 explores Thai culture and its influence on cat, dog, and elephant management as compared with North American norms. The students were housed near Chiang Mai, Thailand at a large animal sanctuary that is residence to over 100 elephants, 600 dogs and 2,000 cats. In ANS 395, students were taught and allowed to participate in basic veterinary techniques including physical exams, blood collections, IV catheter placement, suturing, medical injections, skin scraping, fecal testing, feed intake assessment, and surgical (spay/neuter) preparation. Students were able to interact with numerous animal professionals and rescued animal species in unique situations including cats in large outdoor population holding areas, semi aggressive and / or paralyzed dogs, elephants that had been severely abused, suffered landmine wounds, or were geriatric. Over 90% of the Thai population identifies as Buddhist. This presents a unique animal management learning perspective since Buddhism teaches the avoidance of all work that involves any killing of animals. Therefore, euthanasia is avoided in most veterinary cases. In contrast, many of the unique animal situations discussed above would be considered for individual humane euthanasia in North America. The novelty of ANS 395 for both instructors and students did not allow for research into how the opinions of the students on ethics and animal care may have been altered by the first offering of this course. Students were asked to Likert scale rank their Thailand animal science experience from 1(poor) to 10 (best). The average was 9/10 (n = 17). This indicates that the student’s post-pandemic valued and enjoyed their interactive study abroad experience. However, instructors did note potential post pandemic increases in social interaction difficulties. As this course develops, knowledge from 2022 will allow student assessment on ethical standpoints regarding animal care prior and post travel to understand cultural and animal management opinion changes after real world exposure.}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Wagner, Jenna and Renfro, Ethan and Stine, Jane and Ward, Erica and Ange-van Heugten, Kimberly D.}, year={2023}, month={May} }
 @article{lin_domec_ward_marshall_king_laviner_fox_west_sun_mcnulty_et al._2022, title={Using delta C-13 and delta O-18 to analyze loblolly pine (Pinus taeda L.) response to experimental drought and fertilization (vol 39, pg 1984, 2019)}, volume={42}, ISSN={["1758-4469"]}, DOI={10.1093/treephys/tpab162}, number={4}, journal={TREE PHYSIOLOGY}, author={Lin, Wen and Domec, Jean-Christophe and Ward, Eric J. and Marshall, John and King, John S. and Laviner, Marshall A. and Fox, Thomas R. and West, Jason B. and Sun, Ge and McNulty, Steve and et al.}, year={2022}, month={Apr}, pages={703–703} }
 @article{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={Net primary productivity (NPP) and net ecosystem production (NEP) are often used interchangeably, as their difference, heterotrophic respiration (soil heterotrophic CO2 efflux, RSH = NPP−NEP), is assumed a near‐fixed fraction of NPP. Here, we show, using a range‐wide replicated experimental study in loblolly pine (Pinus taeda) plantations that RSH responds differently than NPP to fertilization and drought treatments, leading to the divergent responses of NPP and NEP. Across the natural range of the species, the moderate responses of NPP (+11%) and RSH (−7%) to fertilization combined such that NEP increased nearly threefold in ambient control and 43% under drought treatment. A 13% decline in RSH under drought led to a 26% increase in NEP while NPP was unaltered. Such drought benefit for carbon sequestration was nearly twofold in control, but disappeared under fertilization. Carbon sequestration efficiency, NEP:NPP, varied twofold among sites, and increased up to threefold under both drought and fertilization.}, 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{qi_markewitz_mcguire_samuelson_ward_2020, title={Throughfall Reduction x Fertilization: Deep Soil Water Usage in a Clay Rich Ultisol Under Loblolly Pine in the Southeast USA}, volume={2}, ISSN={["2624-893X"]}, DOI={10.3389/ffgc.2019.00093}, abstractNote={Forests in the Southeast USA are predicted to experience a moderate decrease in precipitation inputs over this century that may result in soil water deficiency during the growing season. The potential impact of a drier climate on the productivity of managed loblolly pine (Pinus taeda L.) plantations in the Southeast USA is uncertain. Access to water reserves in deep soil during drought periods may help buffer these forests from the effects of water deficits. To better understand the potential impact of drought on deep soil water, we studied the combined effects of throughfall reduction and fertilization on soil water usage in a clay rich Piedmont Ultisol to a depth of 3 m. In a 6-year-old loblolly pine plantation, we applied a throughfall reduction treatment (ambient vs. ~30% throughfall reduction) and a fertilization treatment (no fertilization vs. fertilization). Over 28 months, throughfall reduction lowered soil moisture for all depths and differences were significant in the surface soils (0–0.3 m) (1.2–3.6%) and deep soils (below 2 m) (2.6–3.6%). Fertilization also lowered soil moisture for all depths and differences were significant at 0.3–0.6 m (2.9%) and 1.94–3.06 m (4.5%). Fertilization when combined with the throughfall reduction treatment significantly decreased soil water at 0.1–0.9 m depth. Soils of all depths were rarely depleted of plant available water with the exception of 0–0.1 m, mainly during the growing season. Under throughfall reduction treatment, soil below 0.9 m consistently accounted for more than half of the change in plant available water during months when transpiration exceeded precipitation. When considering the whole soil profile in this clay rich Ultisol, soil water storage buffered transpirational demand in the face of decreasing throughfall input.}, journal={FRONTIERS IN FORESTS AND GLOBAL CHANGE}, author={Qi, Ji and Markewitz, Daniel and McGuire, Mary Anne and Samuelson, Lisa and Ward, Eric J.}, year={2020}, month={Jan} }
 @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={Drought frequency and intensity are projected to increase throughout the Southeastern USA, the natural range of loblolly pine (Pinus taeda L.), and are expected to have major ecological and economic implications. We analyzed the carbon and oxygen isotopic compositions in tree ring cellulose of loblolly pine in a factorial drought (~30% throughfall reduction) and fertilization experiment, supplemented with trunk sap flow, allometry, and microclimate data. We then simulated leaf temperature and applied a multi-dimensional sensitivity analysis to interpret the changes in the oxygen isotope data. This analysis found that the observed changes in tree ring cellulose could only be accounted for by inferring a change in the isotopic composition of the source water, indicating that the drought treatment increased the uptake of stored moisture from earlier precipitation events. The drought treatment also increased intrinsic water-use efficiency, but had no effect on growth, suggesting that photosynthesis remained relatively unaffected despite 19% decrease in canopy conductance. In contrast, fertilization increased growth, but had no effect on the isotopic composition of tree ring cellulose, suggesting that the fertilizer gains in biomass were attributable to greater leaf area, and not to changes in leaf-level gas exchange. The multi-dimensional sensitivity analysis explored model behavior under different scenarios, highlighting the importance of explicit consideration of leaf temperature in the oxygen isotope discrimination (Δ18Oc) simulation, and is expected to expand the inference space of the Δ18Oc models for plant ecophysiological studies.}, 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} }
 @article{fischer_kelley_ward_boone_ashley_domec_williamson_king_2017, title={A critical analysis of species selection and high vs. low-input silviculture on establishment success and early productivity of model short-rotation wood-energy cropping systems}, volume={98}, ISSN={["1873-2909"]}, DOI={10.1016/j.biombioe.2017.01.027}, abstractNote={Most research on bioenergy short rotation woody crops (SRWC) has been dedicated to the genera Populus and Salix. These species generally require relatively high-input culture, including intensive weed competition control, which increases costs and environmental externalities. Widespread native early successional species, characterized by high productivity and good coppicing ability, may be better adapted to local environmental stresses and therefore could offer alternative low-input bioenergy production systems. To test this concept, we established a three-year experiment comparing a widely-used hybrid poplar (Populus nigra × P. maximowiczii, clone ‘NM6’) to two native species, American sycamore (Platanus occidentalis L.) and tuliptree (Liriodendron tulipifera L.) grown under contrasting weed and pest control at a coastal plain site in eastern North Carolina, USA. Mean cumulative aboveground wood production was significantly greater in sycamore, with yields of 46.6 Mg ha−1 under high-inputs and 32.7 Mg ha−1 under low-input culture, which rivaled the high-input NM6 yield of 32.9 Mg ha−1. NM6 under low-input management provided noncompetitive yield of 6.2 Mg ha−1. Sycamore also showed superiority in survival, biomass increment, weed resistance, treatment convergence, and within-stand uniformity. All are important characteristics for a bioenergy feedstock crop species, leading to reliable establishment and efficient biomass production. Poor performance in all traits was found for tuliptree, with a maximum yield of 1.2 Mg ha−1, suggesting this native species is a poor choice for SRWC. We conclude that careful species selection beyond the conventionally used genera may enhance reliability and decrease negative environmental impacts of the bioenergy biomass production sector.}, journal={BIOMASS & BIOENERGY}, author={Fischer, M. and Kelley, A. M. and Ward, E. J. and Boone, J. D. and Ashley, E. M. and Domec, J. -C. and Williamson, J. C. and King, J. S.}, year={2017}, month={Mar}, pages={214–227} }
 @article{ward_domec_king_sun_mcnulty_noormets_2017, title={TRACC: an open source software for processing sap flux data from thermal dissipation probes}, volume={31}, ISSN={["1432-2285"]}, DOI={10.1007/s00468-017-1556-0}, abstractNote={TRACC is an open-source software for standardizing the cleaning, conversion, and calibration of sap flux density data from thermal dissipation probes, which addresses issues of nighttime transpiration and water storage. Thermal dissipation probes (TDPs) have become a widely used method of monitoring plant water use in recent years. The use of TDPs requires calibration to a theoretical zero-flow value (∆T 0); usually based upon the assumption that at least some nighttime measurements represent zero-flow conditions. Fully automating the processing of data from TDPs is made exceedingly difficult due to errors arising from many sources. However, it is desirable to minimize variation arising from different researchers’ processing data, and thus, a common platform for processing data, including editing raw data and determination of ∆T 0, is useful and increases the transparency and replicability of TDP-based research. Here, we present the TDP data processing software TRACC (Thermal dissipation Review Assessment Cleaning and Conversion) to serve this purpose. TRACC is an open-source software written in the language R, using graphical presentation of data and on screen prompts with yes/no or simple numerical responses. It allows the user to select several important options, such as calibration coefficients and the exclusion of nights when vapor pressure deficit does not approach zero. Although it is designed for users with no coding experience, the outputs of TRACC could be easily incorporated into more complex models or software.}, number={5}, journal={TREES-STRUCTURE AND FUNCTION}, author={Ward, Eric J. and Domec, Jean-Christophe and King, John and Sun, Ge and McNulty, Steve and Noormets, Asko}, year={2017}, month={Oct}, pages={1737–1742} }
 @article{johnson_wortemann_mcculloh_jordan-meille_ward_warren_palmroth_domec_2016, title={A test of the hydraulic vulnerability segmentation hypothesis in angiosperm and conifer tree species}, volume={36}, ISSN={["1758-4469"]}, DOI={10.1093/treephys/tpw031}, abstractNote={Water transport from soils to the atmosphere is critical for plant growth and survival. However, we have a limited understanding about many portions of the whole-tree hydraulic pathway, because the vast majority of published information is on terminal branches. Our understanding of mature tree trunk hydraulic physiology, in particular, is limited. The hydraulic vulnerability segmentation hypothesis (HVSH) stipulates that distal portions of the plant (leaves, branches and roots) should be more vulnerable to embolism than trunks, which are nonredundant organs that require a massive carbon investment. In the current study, we compared vulnerability to loss of hydraulic function, leaf and xylem water potentials and the resulting hydraulic safety margins (in relation to the water potential causing 50% loss of hydraulic conductivity) in leaves, branches, trunks and roots of four angiosperms and four conifer tree species. Across all species, our results supported strongly the HVSH as leaves and roots were less resistant to embolism than branches or trunks. However, branches were consistently more resistant to embolism than any other portion of the plant, including trunks. Also, calculated whole-tree vulnerability to hydraulic dysfunction was much greater than vulnerability in branches. This was due to hydraulic dysfunction in roots and leaves at less negative water potentials than those causing branch or trunk dysfunction. Leaves and roots had narrow or negative hydraulic safety margins, but trunks and branches maintained positive safety margins. By using branch-based hydraulic information as a proxy for entire plants, much research has potentially overestimated embolism resistance, and possibly drought tolerance, for many species. This study highlights the necessity to reconsider past conclusions made about plant resistance to drought based on branch xylem only. This study also highlights the necessity for more research of whole-plant hydraulic physiology to better understand strategies of plant drought tolerance and the critical control points within the hydraulic pathway.}, number={8}, journal={TREE PHYSIOLOGY}, author={Johnson, Daniel M. and Wortemann, Remi and McCulloh, Katherine A. and Jordan-Meille, Lionel and Ward, Eric and Warren, Jeffrey M. and Palmroth, Sari and Domec, Jean-Christophe}, year={2016}, month={Aug}, pages={983–993} }
 @article{jiao_lu_sun_ward_fu_2016, title={Biophysical controls on canopy transpiration in a black locust (Robinia pseudoacacia) plantation on the semi-arid Loess Plateau, China}, volume={9}, ISSN={["1936-0592"]}, DOI={10.1002/eco.1711}, abstractNote={In the semi‐arid Loess Plateau of China, black locust (Robinia pseudoacacia) was widely planted for soil conservation and afforestation purposes during the past three decades. Investigating biophysical controls on canopy transpiration (Ec) of the plantations is essential to understanding the effects of afforestation on watershed hydrology and regional water resources. In addition to monitoring of micrometeorology and soil water content, sap flux densities (Fd) of six representative trees in a 27‐year stand were continuously measured using thermal dissipation probes during the growing seasons in 2013 and 2014. Ec was derived by multiplying stand total sapwood area (AST) with Fd. The daily mean Ec in the growing season was 0.14 and 0.23 mm day−1 in 2013 and 2014, respectively. The responses of daily Ec to Rs and vapour pressure deficit were explained with an exponential threshold model. The variability of monthly Ec was mainly explained by leaf area index (LAI) (R2 = 0.92). The inter‐annual variability of Ec was influenced by LAI that fluctuated dramatically during 2013 and 2014. We found that the status of soil water content at the beginning of the growing season had large impacts on LAI and Ec during the growing season. Contrary to common beliefs that the plantation uses a large amount of water, we found that the black locust plantation had rather low transpiration rates (5.3% of precipitation and 4.6% of ET0). This study suggests that the black locust plantation has adapted to local soil water condition by reducing transpiration, and the major water loss from the plantation was not transpiration. Copyright © 2015 John Wiley & Sons, Ltd.}, number={6}, journal={ECOHYDROLOGY}, author={Jiao, Lei and Lu, Nan and Sun, Ge and Ward, Eric J. and Fu, Bojie}, year={2016}, month={Sep}, pages={1068–1081} }
 @article{wightman_martin_gonzalez-benecke_jokela_cropper_ward_2016, title={Loblolly pine productivity and water relations in response to throughfall reduction and fertilizer application on a poorly drained site in Northern Florida}, volume={7}, number={10}, journal={Forests}, author={Wightman, M. G. and Martin, T. A. and Gonzalez-Benecke, C. A. and Jokela, E. J. and Cropper, W. P. and Ward, E. J.}, year={2016} }
 @article{ward_2016, title={Measuring water fluxes in forests: the need for integrative platforms of analysis}, volume={36}, ISSN={["1758-4469"]}, DOI={10.1093/treephys/tpw065}, abstractNote={To understand the importance of analytical tools such as those provided by Berdanier et al. (2016) in this issue of Tree Physiology, one must understand both the grand challenges facing Earth system modelers, as well as the minutia of engaging in ecophysiological research in the field. It is between these two extremes of scale that many ecologists struggle to translate empirical research into useful conclusions that guide our understanding of how ecosystems currently function and how they are likely to change in the future. Likewise, modelers struggle to build complexity into their models that match this sophisticated understanding of how ecosystems function, so that necessary simplifications required by large scales do not themselves change the conclusions drawn from these simulations. As both monitoring technology and computational power increase, along with the continual effort in both empirical and modeling research, the gap between the scale of Earth system models and ecological observations continually closes. This creates a need for platforms of model–data interaction that incorporate uncertainties in both simulations and observations when scaling from one to the other, moving beyond simple comparisons of monthly or annual sums and means. Global models of the Earth system are now approaching the complexity and resolution at which the dynamics of vegetation begin to play a crucial role. The next generation of dynamic global vegetation models (DGVMs) will not just include regional representations of typical ecosystems of different plant functional types (PFTs), but will take into account variation in important plant traits within them (Wullschleger et al. 2014), such as carbon allocation, stomatal regulation, xylem hydraulics, photosynthetic potential and respiration. Indeed, trait variability within PFTs has been shown to change projections of future terrestrial carbon sinks by up to 33% or more (Verheijen et al. 2015), while almost 70% of the variance in FLUXNET (a global database of ecosystem eddy-covariance observations) remain unexplained by classical PFT approach (Reichstein et al. 2014). This level of sophistication is understood as a prerequisite for predicting how ecosystems will adapt to a changing climate, including areas whose climate envelope is pushed beyond the range observed in recorded history. To achieve this, models must move beyond using aggregated observations of different PFTs to fully utilizing the complex record of observations acquired over decades of ecological field and laboratory research. Achieving such data–model interaction requires collaborations between empirical scientists and modelers, as well as those conversant in both types of research. Approaches that harness model–data interaction can be useful in multi-model comparisons (McDowell et al. 2013, Walker et al. 2015), in the design of observational and experimental studies (Medlyn et al. 2016, Norby et al. 2016), and even in selecting the most valuable measurements to transmit to dataloggers (Clark et al. 2011). The software that translates ecophysiological measurements from electrical signals (e.g. millivolts measured by a sensor) to state variables found in DGVMs (e.g. millimeters per day of transpiration) forms an often-overlooked part of model–data interaction and represents a key platform for this integration between physiological ecologists and ecological modelers. It is important to realize that the vast majority of researchers lack formal training in software development yet they may devote 30% of their time to developing domainspecific software to address such issues (Wilson et al. 2014). The assumptions inherent within such software forms a crucial}, number={8}, journal={TREE PHYSIOLOGY}, author={Ward, Eric J.}, year={2016}, month={Aug}, pages={929–931} }
 @article{will_fox_akers_domec_gonzalez-benecke_jokela_kane_laviner_lokuta_markewitz_et al._2015, title={A Range-Wide Experiment to Investigate Nutrient and Soil Moisture Interactions in Loblolly Pine Plantations}, volume={6}, ISSN={["1999-4907"]}, DOI={10.3390/f6062014}, abstractNote={The future climate of the southeastern USA is predicted to be warmer, drier and more variable in rainfall, which may increase drought frequency and intensity. Loblolly pine (Pinus taeda) is the most important commercial tree species in the world and is planted on ~11 million ha within its native range in the southeastern USA. A regional study was installed to evaluate effects of decreased rainfall and nutrient additions on loblolly pine plantation productivity and physiology. Four locations were established to capture the range-wide variability of soil and climate. Treatments were initiated in 2012 and consisted of a factorial combination of throughfall reduction (approximate 30% reduction) and fertilization (complete suite of nutrients). Tree and stand growth were measured at each site. Results after two growing seasons indicate a positive but variable response of fertilization on stand volume increment at all four sites and a negative effect of throughfall reduction at two sites. Data will be used to produce robust process model parameterizations useful for simulating loblolly pine growth and function under future, novel climate and management scenarios. The resulting improved models will provide support for developing management strategies to increase pine plantation productivity and carbon sequestration under a changing climate.}, number={6}, journal={FORESTS}, author={Will, Rodney E. and Fox, Thomas and Akers, Madison and Domec, Jean-Christophe and Gonzalez-Benecke, Carlos and Jokela, Eric J. and Kane, Michael and Laviner, Marshall A. and Lokuta, Geoffrey and Markewitz, Daniel and et al.}, year={2015}, month={Jun}, pages={2014–2028} }
 @article{bell_ward_oishi_oren_flikkema_clark_2015, title={A state-space modeling approach to estimating canopy conductance and associated uncertainties from sap flux density data}, volume={35}, ISSN={["1758-4469"]}, DOI={10.1093/treephys/tpv041}, abstractNote={Uncertainties in ecophysiological responses to environment, such as the impact of atmospheric and soil moisture conditions on plant water regulation, limit our ability to estimate key inputs for ecosystem models. Advanced statistical frameworks provide coherent methodologies for relating observed data, such as stem sap flux density, to unobserved processes, such as canopy conductance and transpiration. To address this need, we developed a hierarchical Bayesian State-Space Canopy Conductance (StaCC) model linking canopy conductance and transpiration to tree sap flux density from a 4-year experiment in the North Carolina Piedmont, USA. Our model builds on existing ecophysiological knowledge, but explicitly incorporates uncertainty in canopy conductance, internal tree hydraulics and observation error to improve estimation of canopy conductance responses to atmospheric drought (i.e., vapor pressure deficit), soil drought (i.e., soil moisture) and above canopy light. Our statistical framework not only predicted sap flux observations well, but it also allowed us to simultaneously gap-fill missing data as we made inference on canopy processes, marking a substantial advance over traditional methods. The predicted and observed sap flux data were highly correlated (mean sensor-level Pearson correlation coefficient = 0.88). Variations in canopy conductance and transpiration associated with environmental variation across days to years were many times greater than the variation associated with model uncertainties. Because some variables, such as vapor pressure deficit and soil moisture, were correlated at the scale of days to weeks, canopy conductance responses to individual environmental variables were difficult to interpret in isolation. Still, our results highlight the importance of accounting for uncertainty in models of ecophysiological and ecosystem function where the process of interest, canopy conductance in this case, is not observed directly. The StaCC modeling framework provides a statistically coherent approach to estimating canopy conductance and transpiration and propagating estimation uncertainty into ecosystem models, paving the way for improved prediction of water and carbon uptake responses to environmental change.}, number={7}, journal={TREE PHYSIOLOGY}, author={Bell, David M. and Ward, Eric J. and Oishi, A. Christopher and Oren, Ram and Flikkema, Paul G. and Clark, James S.}, year={2015}, month={Jul}, pages={792–802} }
 @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{ward_domec_laviner_fox_sun_mcnulty_king_noormets_2015, title={Fertilization intensifies drought stress: Water use and stomatal conductance of Pinus taeda in a midrotation fertilization and throughfall reduction experiment}, volume={355}, ISSN={["1872-7042"]}, DOI={10.1016/j.foreco.2015.04.009}, abstractNote={While mid-rotation fertilization increases productivity in many southern pine forests, it remains unclear what impact such management may have on stand water use. We examined the impact of nutrient and water availability on stem volume, leaf area, transpiration per unit ground area (EC) and canopy conductance per unit leaf area (GS) of a pine plantation during its 8th and 9th growing seasons. Treatments consisted of a factorial combination of throughfall reduction (30% reduction in throughfall versus ambient) and fertilization (a complete suite of essential nutrients) beginning in April 2012. Overall, our results indicate that despite unusually high rainfall in the study period and a lack of leaf area index (LAI) response, both EC and GS decreased in response to fertilization and throughfall reduction. Fertilization increased stem volume increment 21% in 2013. Treatment differences were greatest in the growing season of 2013, when EC was on average 19%, 13% and 29% lower in the throughfall reduction (D), fertilization (F) and combined treatment (FD) than the control (C), respectively. The responses of GS to volumetric soil water content (VWC) indicate that lower EC in F was associated with a decrease relative to C in GS at high VWC. Decreases of GS in D relative to C were associated with lower VWC, but little change in the response of GS to VWC. Decreases observed in FD resulted from a combination of these two factors. The pattern of GS responses in the different treatments suggests that structural or physiological changes underlie this fertilization response, possibly in fine root area or hydraulic conductivity. In the short term, this led to large increases in the water use efficiency of stem production, which could suggest greater resiliency to minor water stress. However, impacts on long-term sensitivity to drought remain a concern, as the EC reduction triggered by the fertilization treatment was of comparable magnitude to the 30% throughfall exclusion treatment and the greatest reductions were found in the combined treatment.}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Ward, Eric J. and Domec, Jean-Christophe and Laviner, Marshall A. and Fox, Thomas R. and Sun, Ge and McNulty, Steve and King, John and Noormets, Asko}, year={2015}, month={Nov}, pages={72–82} }
 @article{tor-ngern_oren_ward_palmroth_mccarthy_domec_2015, title={Increases in atmosphericCO(2) have little influence on transpiration of a temperate forest canopy}, volume={205}, ISSN={["1469-8137"]}, DOI={10.1111/nph.13148}, abstractNote={Models of forest energy, water and carbon cycles assume decreased stomatal conductance with elevated atmospheric CO2 concentration ([CO2]) based on leaf-scale measurements, a response not directly translatable to canopies. Where canopy-atmosphere are well-coupled, [CO2 ]-induced structural changes, such as increasing leaf-area index (LD), may cause, or compensate for, reduced mean canopy stomatal conductance (GS), keeping transpiration (EC) and, hence, runoff unaltered. We investigated GS responses to increasing [CO2] of conifer and broadleaved trees in a temperate forest subjected to 17-yr free-air CO2 enrichment (FACE; + 200 μmol mol(-1)). During the final phase of the experiment, we employed step changes of [CO2] in four elevated-[CO2 ] plots, separating direct response to changing [CO2] in the leaf-internal air-space from indirect effects of slow changes via leaf hydraulic adjustments and canopy development. Short-term manipulations caused no direct response up to 1.8 × ambient [CO2], suggesting that the observed long-term 21% reduction of GS was an indirect effect of decreased leaf hydraulic conductance and increased leaf shading. Thus, EC was unaffected by [CO2] because 19% higher canopy LD nullified the effect of leaf hydraulic acclimation on GS . We advocate long-term experiments of duration sufficient for slow responses to manifest, and modifying models predicting forest water, energy and carbon cycles accordingly.}, number={2}, journal={NEW PHYTOLOGIST}, author={Tor-ngern, Pantana and Oren, Ram and Ward, Eric J. and Palmroth, Sari and McCarthy, Heather R. and Domec, Jean-Christophe}, year={2015}, month={Jan}, pages={518–525} }
 @article{novick_oishi_ward_siqueira_juang_stoy_2015, title={On the difference in the net ecosystem exchange of CO2 between deciduous and evergreen forests in the southeastern United States}, volume={21}, ISSN={["1365-2486"]}, DOI={10.1111/gcb.12723}, abstractNote={The southeastern United States is experiencing a rapid regional increase in the ratio of pine to deciduous forest ecosystems at the same time it is experiencing changes in climate. This study is focused on exploring how these shifts will affect the carbon sink capacity of southeastern US forests, which we show here are among the strongest carbon sinks in the continental United States. Using eight‐year‐long eddy covariance records collected above a hardwood deciduous forest (HW) and a pine plantation (PP) co‐located in North Carolina, USA, we show that the net ecosystem exchange of CO2 (NEE) was more variable in PP, contributing to variability in the difference in NEE between the two sites (ΔNEE) at a range of timescales, including the interannual timescale. Because the variability in evapotranspiration (ET) was nearly identical across the two sites over a range of timescales, the factors that determined the variability in ΔNEE were dominated by those that tend to decouple NEE from ET. One such factor was water use efficiency, which changed dramatically in response to drought and also tended to increase monotonically in nondrought years (P < 0.001 in PP). Factors that vary over seasonal timescales were strong determinants of the NEE in the HW site; however, seasonality was less important in the PP site, where significant amounts of carbon were assimilated outside of the active season, representing an important advantage of evergreen trees in warm, temperate climates. Additional variability in the fluxes at long‐time scales may be attributable to slowly evolving factors, including canopy structure and increases in dormant season air temperature. Taken together, study results suggest that the carbon sink in the southeastern United States may become more variable in the future, owing to a predicted increase in drought frequency and an increase in the fractional cover of southern pines.}, number={2}, journal={GLOBAL CHANGE BIOLOGY}, author={Novick, Kimberly A. and Oishi, A. Christopher and Ward, Eric J. and Siqueira, Mario B. S. and Juang, Jehn-Yih and Stoy, Paul C.}, year={2015}, month={Feb}, pages={827–842} }