@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}, 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}, 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}, abstractNote={Wildland fires in the contiguous United States (CONUS) have increased in size and severity, but much remains unclear about the impact of fire size and burn severity on water supplies used for drinking, irrigation, industry, and hydropower. While some have investigated large-scale fire patterns, long-term effects on runoff, and the simultaneous effect of fire and climate trends on surface water yield, no studies account for all these factors and their interactions at the same time. In this report, we present critical new information for the National Cohesive Wildland Fire Management Strategy—a first-time CONUS-wide assessment of observed and potential wildland fire impacts on surface water yield. First, we analyzed data from 168 fire-affected locations, collected between 1984 and 2013, with machine learning and used climate elasticity models to correct for the local climate baseline impact. Stream gage data show that annual river flow increased most in the Lower Mississippi and Lower and Upper Colorado water resource regions, however they do not show which portion of this increase is caused by fire and which portion results from local climate trends. Our machine learning model identified local climate trends as the main driver of water yield change and determined wildland fires must affect at least 19 percent of a watershed >10 km2 to change its annual water yield. A closer look at 32 locations with fires covering at least 19 percent of a watershed >10 km2 revealed that wildfire generally enhanced annual river flow. Fires increased river flow relatively the most in the Lower Colorado, Pacific Northwest, and California regions. In the Lower Colorado and Pacific Northwest regions, flow increased despite post-fire drought conditions. In southern California, post-fire drought effects masked the flow enhancement attributed to wildfire, meaning that annual water yield declined but not as much as expected based on the decline in precipitation. Prescribed burns in the Southeastern United States did not produce a widespread effect on river flow, because the area affected was typically too small and characterized by only low burn severity. In the second stage of the assessment, we performed full-coverage simulations of the CONUS with the Water Supply Stress Index (WaSSI) hydrologic model (88,000 HUC-12-level watersheds) for the period between 2001 and 2010. This enables us to fill in the gaps of areas with scarce data and to identify regions with large potential increases in post-fire annual water yield (+10 to +50 percent): midto high-elevation forests in northeastern Washington, northwestern Montana, central Minnesota, southern Utah, Colorado, and South Dakota, and coastal forests in Georgia and northern Florida. A hypothetical 20-percent forest burn impact scenario for the CONUS suggests that surface yield can increase up to +10 percent in most watersheds, and even more in some watersheds depending on climate, soils, and vegetation. The insights gained from this quantitative analysis have major implications for flood mitigation and watershed restoration, and are vital to forest management policies aimed at reducing fire impact risk and improving water supply under a changing climate.}, institution={U.S. Department of Agriculture, Forest Service, Southern Research Station}, author={Hallema, Dennis and Sun, Ge and Caldwell, Peter and Robinne, Francois-Nicolas and Bladon, Kevin D. and Norman, Steve and Liu, Yongqiang and Cohen, Erika C. and McNulty, Steve}, year={2019} }
 @article{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 cm 3 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}, abstractNote={Wetland restoration projects attempt to recreate the hydrology found in natural wetlands, but little is known of the water budgets associated with wetlands in their natural state. The objective of this study was to compute the water budgets of three natural Carolina bay wetlands in Bladen County, North Carolina, USA. DRAINMOD models of various locations in the bays were calibrated with measured water table depths over a 2-yr period using inputs of rainfall, air temperature, and soil physical properties. The models were successful in simulating water table depths at all well locations during the calibration period with average absolute deviations between simulated and measured water table depths of approximately 4 cm. Measured and simulated data revealed very shallow (< 0.1 m) water table depths at all of the bays. Groundwater inflow was a significant component of the water balance at locations near the perimeters of the bays, ranging from 3%–26% of the total water input for these sites during the study period. A semi-confined aquifer below one of the bays was likely the source of groundwater inflow for that bay. Meanwhile, locations near the centers of the bays did not have groundwater inflow as an input to their water budgets. Groundwater outflow for the centers of the bays ranged from 2%–21% of rainfall. Areas near the perimeters of the bays were recharge, discharge, or flow-through wetlands depending on hydrologic conditions at the sites. Areas near the centers of the bays exhibited characteristics of recharge wetlands only. These results were consistent across the three Carolina bays studied, and can be used to better understand the hydrology of natural Carolina bays, improving the success of restoration projects of similar sites.}, 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} }