@article{greenberg_moorman_elliott_martin_hopey_caldwell_2023, title={Breeding bird abundance and species diversity greatest in high-severity wildfire patches in central hardwood forests}, volume={529}, ISSN={["1872-7042"]}, DOI={10.1016/j.foreco.2022.120715}, abstractNote={In 2016, mixed-severity wildfires in the southern Appalachians created a gradient of forest structures not typical following prescribed burns, providing a unique opportunity to study temporally dynamic conditions and breeding bird response. We measured forest structure and breeding bird communities across a fire-severity gradient in 3 burned and 3 unburned watersheds for 5 years (Y1-Y5). We categorized plots as unburned (NB), low- (L), moderate- (M), or high-severity (H) using a composite fire-severity index. Tree mortality increased with fire-severity category (FSC) and over time; by Y5, 7 % of trees in NB, 11 % in L, 38 % in M, and 71 % in H had died. Shrub recovery was rapid and most pronounced in H, exceeding other FSCs (70 % vs 21 %–44 %) by Y5. Total bird abundance, species richness, and diversity increased over time in H (by Y3) and M (by Y4); by Y5, these metrics were highest in H and twice as high in H as in NB. Low-severity wildfires had no detectable effects on birds. Abundance of 7 species was greatest in higher-severity FSCs; 11 species did not differ among FSC, although ovenbirds (Seiurus aurocapilla) indicated a trend of lower abundance in H. No species was limited to NB, L, or M, whereas disturbance-dependent indigo bunting (Passerina cyanea), chestnut-sided warbler (Setophaga pensylvanica), and eastern towhee (Pipilo erythrophthalmus) were primarily associated with H. Increased richness and diversity were associated with heavy tree mortality and subsequent shrub recovery in H, accompanied by an influx of disturbance-dependent species and positive or neutral responses by most other species. Results highlight the interrelated roles of fire severity and time in driving forest structure and breeding bird response. Breeding birds responded to high-severity burns similarly to silvicultural treatments with heavy canopy reduction documented in other studies, offering possible alternatives when managing for breeding bird diversity in hardwood forests.}, journal={FOREST ECOLOGY AND MANAGEMENT}, publisher={Elsevier BV}, author={Greenberg, Cathryn H. and Moorman, Christopher E. and Elliott, Katherine J. and Martin, Katherine and Hopey, Mark and Caldwell, Peter V}, year={2023}, month={Feb} }
 @article{caldwell_martin_vose_baker_warziniack_costanza_frey_nehra_mihiar_2023, title={Forested watersheds provide the highest water quality among all land cover types, but the benefit of this ecosystem service depends on landscape context}, volume={882}, ISSN={["1879-1026"]}, DOI={10.1016/j.scitotenv.2023.163550}, abstractNote={Conversion of natural land cover can degrade water quality in water supply watersheds and increase treatment costs for Public Water Systems (PWSs), but there are few studies that have fully evaluated land cover and water quality relationships in mixed use watersheds across broad hydroclimatic settings. We related upstream land cover (forest, other natural land covers, development, and agriculture) to observed and modeled water quality across the southeastern US and specifically at 1746 PWS drinking water intake facilities. While there was considerable complexity and variability in the relationship between land cover and water quality, results suggest that Total Nitrogen (TN), Total Phosphorus (TP) and Suspended Sediment (SS) concentrations decrease significantly with increasing forest cover, and increase with increasing developed or agricultural cover. Catchments with dominant (>90 %) agricultural land cover had the greatest export rates for TN, TP, and SS based on SPARROW model estimates, followed by developed-dominant, then forest- and other-natural-dominant catchments. Variability in modeled TN, TP, and SS export rates by land cover type was driven by variability in natural background sources and catchment characteristics that affected water quality even in forest-dominated catchments. Both intake setting (i.e., run-of-river or reservoir) and upstream land cover were important determinants of water quality at PWS intakes. Of all PWS intakes, 15 % had high raw water quality, and 85 % of those were on reservoirs. Of the run-of-river intakes with high raw water quality, 75 % had at least 50 % forest land cover upstream. In addition, PWS intakes obtaining surface water supply from smaller upstream catchments may experience the largest losses of natural land cover based on projections of land cover in 2070. These results illustrate the complexity and variability in the relationship between land cover and water quality at broad scales, but also suggest that forest conservation can enhance the resilience of drinking water supplies.}, journal={SCIENCE OF THE TOTAL ENVIRONMENT}, author={Caldwell, Peter V. and Martin, Katherine L. and Vose, James M. and Baker, Justin S. and Warziniack, Travis W. and Costanza, Jennifer K. and Frey, Gregory E. and Nehra, Arpita and Mihiar, Christopher M.}, year={2023}, 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 Clean water from forests is commonly used to supply drinking water to communities both within and outside basin boundaries through inter‐basin transfers (IBTs). Here, we modified the Water Supply Stress Index (WaSSI) model to provide estimates of mean water yield and the proportion of mean flow originating on forested lands at the 12‐Digit Hydrologic Unit Code scale across the conterminous United States (CONUS). We accounted for the benefits of forests for drinking water supply and receiving populations through IBTs by incorporating a new IBT database, surface intake location information for public drinking water systems, and modeled water yield from forests. We compiled the new database of 594 IBTs ranging from 0.01 million m 3 yr −1 to 8,900 million m 3 yr −1 , for a total transferred volume of 116,894 million m 3 yr −1 . According to our results, forested lands comprised 28.7% of the total land area across CONUS, but contributed 46% of the total surface water yield. Approximately 125.5 million people derived more than 10% of their surface drinking water supply from forested lands, and 83.1 million people received more than 50% of their surface drinking water supply from forested lands. Of those 83.1 million people receiving more than 50% of their surface drinking water supply from forested lands, 19.4 million people obtained some (≥0.01%) of that water through IBTs. We conclude that accounting for IBTs is critical to accurately assess the contribution of forested watersheds for surface drinking water supply. Hydrologic models for assessment and decision making must include IBTs to fully account for the effects of climate change and human population dynamics on water resource availability at watershed to regional scales. Results from this study can aid water resource and forest managers in developing integrated watershed management plans at a time when climate change, population growth, and land use change threaten water supplies.}, 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{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 Forests provide the most stable and highest quality water supplies among all land uses. Quantitatively evaluating the benefits of forest water supply functions is important to effectively mitigate the impacts of land development, climate change, and population growth. Here, by integrating a water balance model and national drinking water data, we determined the amount of surface water yield originating on different forest ownership types at a fine resolution (88,000 watersheds) and tracked that water through the river network to drinking water intakes and the populations they serve. We found that forested lands comprised 36% of the total land area but contributed 50% of the total surface water yield. Of the 23,983 public surface drinking water intakes depending on surface water sources, 89% (serving around 150 million people) received some (>0.01%) surface water from forested lands, and 38% (serving about 60 million people) received more than 50% of their surface drinking water supply from forested lands. Privately-owned forests were the most important water source in the eastern U.S., benefiting 16 million people, followed by federal forests (14.4% of the total water supply). In contrast, federally-owned forested lands were the dominant water source (52% of the total water supply) in the West. Privately-owned forests are the most vulnerable to future land use change and associated water supply impacts. Continuing programs that support private forest landowners with financial and technical assistance through federal and state forest management agencies and potentially developing payment for ecosystem service schemes could maximize benefits for landowners so they may retain their land assets while minimizing forest loss and associated impacts on critical ecosystem services including the provisioning a clean and reliable water supply for the American public.}, 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{vepraskas_skaggs_caldwell_2020, title={Method to Assess Climate Change Impacts on Hydrologic Boundaries of Individual Wetlands}, volume={40}, ISSN={["1943-6246"]}, url={https://doi.org/10.1007/s13157-019-01183-6}, DOI={10.1007/s13157-019-01183-6}, number={2}, journal={WETLANDS}, publisher={Springer Science and Business Media LLC}, author={Vepraskas, M. J. and Skaggs, R. W. and Caldwell, P.}, year={2020}, month={Apr}, pages={365–376} }
 @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{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} }
 @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}, 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{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{vepraskas_caldwell_2008, title={Interpreting morphological features in wetland soils with a hydrologic model}, volume={73}, ISSN={["1872-6887"]}, DOI={10.1016/j.catena.2007.07.005}, abstractNote={Wetlands in the United States are protected by law and are identified by their hydric soils, wetland hydrology, and vegetation. Hydric soils are easily identified by color characteristics termed hydric soil field indicators, that form under saturated and anaerobic conditions, but wetland hydrology is difficult to assess. This study determines how often seven hydric soil field indicators met wetland hydrology requirements which require a water table be within 30 cm of the surface for 14 days or more during the growing season in over half the years. Studies were conducted at five sites in North Carolina in both wetland and upland plots. Soils ranged from Aquic Paleudults to Typic Haplosaprists across all sites. The water-table simulation model DRAINMOD was calibrated to soil conditions in individual plots. Long-term rainfall data were used with the calibrated models to compute 40 years of daily water table data to represent both wet and dry years. It was found that the hydric soils with field indicators composed of organic materials in layers over 20 cm thick (Histosol and Histic epipedon field indicators) met wetland hydrology requirements each year, and in addition were ponded with water for periods between 67 to 139 days on average each year during the growing season. Plots in mineral soils having the Dark Surface (S7) indicator as well as the Sandy Mucky Mineral (S1) indicator also met the saturation requirements for wetland hydrology every year, and were ponded for only 3 days per year on average. Other mineral soils with an Umbric Surface (F13) or a Depleted Matrix (F3) field indicator met wetland hydrology requirements in approximately 95% of the years, and had water tables within 30 cm of the surface for 40 days per year on average. The Redox Depressions (F8) field indicator occurred in a small depression that was saturated for 87% of the year for periods averaging approximately 30 days. These results showed that hydric soil field indicators can be calibrated to long-term water table data that will allow precise assessments of wetland hydrology on-site.}, number={2}, journal={CATENA}, author={Vepraskas, M. J. and Caldwell, P. V.}, year={2008}, month={Apr}, pages={153–165} }
 @article{caldwell_vepraskas_gregory_2007, title={Physical properties of natural organic soils in Carolina Bays of the southeastern United States}, volume={71}, ISSN={["0361-5995"]}, DOI={10.2136/sssaj2006.0108}, abstractNote={Hydrologic models are useful tools for designing wetland restoration projects, but they are difficult to use for sites with natural organic soils because few soil property data are available for these soils. The objective of this study was to measure the physical properties of organic soils needed to calibrate hydrologic models of three natural Carolina Bay wetlands in the southeastern USA. Undisturbed soil cores were collected at each site for laboratory measurement of saturated hydraulic conductivity, soil water characteristic curves, bulk density, particle density, and total porosity. Field measurements of saturated hydraulic conductivity were also made. The Oi, Oe, and Oa horizons in the natural organic soils had similar bulk densities (0.16 g cm−3), total porosities (0.90 cm3 cm−3), and particle densities (1.50 g cm−3). However, field-measured saturated hydraulic conductivities decreased as the level of decomposition increased, going from 45 to 7.1 to 1.5 cm h−1 for the Oi, Oe, and Oa horizons, respectively. Soil water characteristic data revealed an abundance of large pores (>0.3 mm) in the Oi horizons, which likely explains their high saturated hydraulic conductivity relative to the Oe and Oa horizons, which had fewer large pores. Using the data collected in this study, mathematical relationships were developed to predict the total porosity and the saturated hydraulic conductivity of these organic soils based on more easily obtainable data, such as bulk density and the organic horizon type.}, number={3}, journal={SOIL SCIENCE SOCIETY OF AMERICA JOURNAL}, author={Caldwell, P. V. and Vepraskas, M. J. and Gregory, J. D.}, year={2007}, pages={1051–1057} }
 @article{caldwell_vepraskas_skaggs_gregory_2007, title={Simulating the water budgets of natural Carolina bay wetlands}, volume={27}, ISSN={["0277-5212"]}, DOI={10.1672/0277-5212(2007)27[1112:stwbon]2.0.co;2}, number={4}, journal={WETLANDS}, author={Caldwell, Peter V. and Vepraskas, Michael J. and Skaggs, R. Wayne and Gregory, James D.}, year={2007}, month={Dec}, pages={1112–1123} }
 @article{caldwell_adams_niewoehner_vepraskas_gregory_2005, title={Sampling device to extract intact cores in saturated organic soils}, volume={69}, ISSN={["1435-0661"]}, DOI={10.2136/sssaj2005.0150}, abstractNote={Physical property data on organic soils are lacking due to difficulty in collecting undisturbed samples from these frequently saturated and weakly consolidated soils. A sampling device was constructed to extract undisturbed cores from saturated organic soils in a forested setting. The sampler consists of a 100‐cm‐long, 7.6‐cm‐diam. schedule 40 PVC pipe that was fitted with female threaded adapters on either end. A cutting head was constructed to cut through the fibric root mat and other woody debris in the profile by gluing a 7.6‐cm‐diam. hole‐saw to a male threaded adaptor that was attached to the PVC pipe. The sampler was rotated by hand into the organic soil with gentle downward pressure. When the desired depth was reached, the remaining air space in the PVC pipe was filled with water and a threaded cap was used to seal the top of the sampler. A 1.3‐cm‐diam. galvanized pipe was inserted next to the sampler to add water to the bottom of the core, relieving the suction created as the core was pulled from the soil. The sampler and vent pipe were pulled from the soil either by hand or with a tripod–winch arrangement. Before the cutting head was raised above the water table, it was removed and replaced with another threaded PVC cap. The 100‐cm‐long pipe containing the soil core was then cut into 7.6‐cm‐long sections using a wheel‐type PVC pipe cutter. Saturated hydraulic conductivity and soil water characteristics were then measured in the laboratory using the resulting 7.6‐cm‐long samples encased in the PVC cylinders.}, number={6}, journal={SOIL SCIENCE SOCIETY OF AMERICA JOURNAL}, author={Caldwell, PV and Adams, AA and Niewoehner, CP and Vepraskas, MJ and Gregory, JD}, year={2005}, pages={2071–2075} }