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Loren M. Smith - One of the best experts on this subject based on the ideXlab platform.
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effects of sediment removal and surrounding land use on carbon and nitrogen storage in Playas and watersheds in the rainwater basin region of nebraska
Soil & Tillage Research, 2017Co-Authors: Dale W Daniel, Loren M. Smith, Scott T McmurryAbstract:Abstract Eroded soil from cropland watersheds is deposited as sediment into depressional wetlands such as Playas degrading their ability to provide ecosystem services. Sediment removal from these degraded playa wetlands restores water storage volume. However, the effects of this restoration practice on carbon (C) and nitrogen (N) concentrations and C sequestration potential in Playas has not been determined. One of the most important wetland systems and intensively cultivated regions in North America, the Rainwater Basin (RWB) of Nebraska, contained over 4000 Playas but has lost 90% of them due to agricultural activities. Our objective was to examine the effects of sediment removal on wetland C and N concentrations and determine subsequent C sequestration potential. We also were interested in determining the importance of the presence of wetlands on the landscape to C sequestration given the loss of wetlands that has occurred. We hypothesized that sediment removal might decrease C sequestration potential and that the presence of wetlands on the landscape provides important C sequestration sites. To accomplish these objectives we sampled 60 Playas and their immediate watersheds (20 each from reference condition, cropland, and restored through sediment removal) in 2013 and 2014 by coring soil/sediments (mollisols) to a depth of 50 cm. Restored Playas contained 29% lower C and N in the top 5 cm than in reference and cropland land uses. The C in the top 5 cm was also 36% higher in the wetland than in the watershed. There were no differences in C and N among land uses/landscape positions at depths >5 cm. However, because restored Playas had sediment removed, in some cases down to the clay pan of the historic playa soil surface, on an areal basis, restored Playas stored 21% more soil organic carbon (SOC) in deeper horizons (25–50 cm) than reference or cropland conditions. Overall, SOC was similar among restored, cropland and reference wetlands to a 50 cm depth, indicating that sediment removal does not have a negative effect on C sequestration potential. On average, SOC was 15% higher in Playas than in adjacent uplands, demonstrating the importance of playa wetlands on the landscape to C sequestration. Results of this study have widespread applicability because depressional wetlands are the dominant wetland type in temperate agroecosystems.
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soil organic carbon in Playas and adjacent prairies cropland and conservation reserve program land of the high plains usa
Soil & Tillage Research, 2016Co-Authors: Jessica L Oconnell, Scott T Mcmurry, Dale W Daniel, Loren M. SmithAbstract:Abstract Soil organic carbon (SOC) is an important reservoir for atmospheric CO2 associated with climate warming. The High Plains, USA, lacks region-wide SOC estimates within playa wetlands and their adjacent watershed. Croplands often have less SOC than grasslands, and the Conservation Reserve Program (CRP; former croplands planted to grass) may return SOC. Our goals were to estimate SOC within playa wetlands and investigate small scale differences within wetland catchments across a broad agriculturally modified landscape. We estimated SOC (kg m−2) to 50 cm depth from 4 soil cores/catchment (in Playas and 10, 40 and 100 m into uplands) at 56, 52, and 54 sites in native grassland, CRP and cropland, respectively. At a subset of sample locations within each land use type, we estimated SOC to 1 m depth to characterize SOC missed by shallow sampling. In playa wetlands, CRP SOC from 0 to 50 cm was 18% greater than croplands, but native grassland playa SOC did not differ from other land-uses. From 0 to 1 m, SOC in native grassland wetlands and uplands was 20% greater than the same habitats within croplands, while CRP lands were intermediate. Native grassland playa SOC also was 16% greater than in surrounding native short grass prairie. Playas therefore represent an important SOC repository in the High Plains ecoregion. CRP Playas and uplands may require an additional 10–30 years to resemble native grassland SOC. SOC increased with playa area throughout CRP and native grassland catchments, suggesting playa hydrogeomorphology influences adjacent upland SOC. High Plains Playas store 20.8 Tg C and cropland conversion caused a cumulative loss of 2.0 Tg C from 82,000 ha of Playas. Currently, CRP enrollment on over 25,000 ha of Playas has returned 0.2 Tg C (95% CI: 0.1–0.3), only half the historic SOC lost by cropland conversion within CRP Playas. To promote SOC storage, native grasslands and large Playas should be preserved and CRP enrollments should be maintained over long timescales.
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land use effects on sedimentation and water storage volume in Playas of the rainwater basin of nebraska
Land Use Policy, 2015Co-Authors: Dale W Daniel, Loren M. Smith, Scott T McmurryAbstract:A region dominated by cropland, the Rainwater Basin (RWB) of Nebraska, contains playa wetlands of international importance but estimates of historic wetland numbers suggest that approximately 90% of wetlands have been lost through draining and filling. To reverse these losses and restore their ecosystem services, >2000 ha of wetlands in the RWB have been enrolled into the US Department of Agriculture (USDA) Wetlands Reserve Program (WRP). Our goal was to compare water storage volume and sediment loads in RWB Playas in surrounding cropland, reference condition, and restored (WRP) land uses. To do so, we measured characteristics of 48 Playas that dictate water storage capabilities essential to their service provisioning (historic/current playa area, playa volume, and sediment depth to clay pan). Using historic wetland hydric soil footprints, we determined loss of historic area for wetlands in each land use type and using soil cores we estimated sediment depth and volume loss. Reference condition Playas had 380% more functional wetland area and 8 times more volume than cropland Playas, WRP Playas were intermediate between reference and cropland Playas. In addition, reference condition Playas had lost the least amount of historic area (65%) followed by WRP (70%) and cropland (83%). Though cropland Playas lost the greatest extent of historic wetland area, they had sediment depths (to Bt layer) similar to Playas embedded in reference and WRP, indicating that all Playas in the region have been impacted by watershed soil erosion. In order to increase the overall positive impact on wetland services provided by enrolling Playas into the WRP, conservation practitioners should remove sediments down to the Bt layer in enrolled wetlands in the RWB and protect the immediate watershed to prevent further erosion.
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Amphibian community responses to playa restoration in the rainwater basin
Wetlands, 2014Co-Authors: Benjamin J. Beas, Loren M. SmithAbstract:Alterations to wetland hydrology associated with conversion of grassland watersheds to croplands can alter functional components that drive many wetland ecosystem services. Biodiversity provisioning is one of many services that can be negatively impacted by grassland conversions. Our objective was to compare amphibian communities of playa wetlands in native grassland versus cropland watersheds and to determine if restoration of cropland wetlands via sediment removal improved these habitats for amphibians. We collected amphibian species richness, water depth, wetland area, and emergent plant cover data from 34 playa wetlands in 2008 and 32 playa wetlands in 2009. Playas were selected to include those within natural grassland watersheds (i.e., reference Playas), cropland watersheds, and restored watersheds within the Rainwater Basin (RWB) of Nebraska. While we did not detect a difference in amphibian species richness among land-use types in 2008, in 2009 (a dry year within the RWB) amphibian species richness averaged nearly two times greater in restored Playas (3.18) compared to cropland Playas (1.70). Average water depth (2008 and 2009) and playa area (2008 only) were best predictors of amphibian species richness. Restored Playas provided the most reliable water availability for amphibians in the RWB where 90 % of the wetlands have been drained.
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physical loss and modification of southern great plains Playas
Journal of Environmental Management, 2012Co-Authors: Lacrecia A Johnson, Loren M. Smith, David A. Haukos, Scott T McmurryAbstract:Abstract Playas are the primary wetland system in the Southern Great Plains (SGP) of North America providing critical stopover habitats for migratory birds in the Western Hemisphere. Collectively, these wetlands form the keystone ecosystem in this region supporting biodiversity for North America and provide habitat for native plants and animals that are essential for maintenance of international biological diversity along with other local and regional ecological services. Large-scale landscape changes in this region, primarily as a result of agriculturally-based anthropogenic impacts, threaten Playas with functional loss and physical extinction. These impacts are not considered in current estimates of the number of extant functional Playas, leading to biased estimates by groups or agencies extrapolating research or monitoring results, conducting conservation planning, and modeling impacts of future climate change. Using a combination of stochastic and empirical data, we identified impacts to Playas and playa watersheds and quantified the extent and rate of these impacts relative to physical loss. Only 0.2% of Playas had no wetland or watershed modification and we conservatively estimate that 17% of Playas recently existing on the landscape no longer are represented by an apparent depression. With the inclusion of sediment volume estimates where ≥100% of the volume of original differentiated playa soil has been filled, 60% or 16,855 Playas have been physically lost from the SGP despite a continued presence of a depression. Data also show that small Playas are being lost more rapidly than larger ones; the average size (±SE) of extant Playas has increased from 7.5 ± 0.47 to 8.5 ± 0.55 ha. The reduced ecological condition of 95.3% of Playas remaining on the landscape exceeds historical predictions of a maximum 85% of Playas ever being modified. Given the results of this study these changes can now be accounted for, resulting in more informed management and conservation of Playas and bring awareness to the urgency of implementation of effective conservation measures for Playas and the species that depend on this keystone ecosystem.
Scott T Mcmurry - One of the best experts on this subject based on the ideXlab platform.
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effects of sediment removal and surrounding land use on carbon and nitrogen storage in Playas and watersheds in the rainwater basin region of nebraska
Soil & Tillage Research, 2017Co-Authors: Dale W Daniel, Loren M. Smith, Scott T McmurryAbstract:Abstract Eroded soil from cropland watersheds is deposited as sediment into depressional wetlands such as Playas degrading their ability to provide ecosystem services. Sediment removal from these degraded playa wetlands restores water storage volume. However, the effects of this restoration practice on carbon (C) and nitrogen (N) concentrations and C sequestration potential in Playas has not been determined. One of the most important wetland systems and intensively cultivated regions in North America, the Rainwater Basin (RWB) of Nebraska, contained over 4000 Playas but has lost 90% of them due to agricultural activities. Our objective was to examine the effects of sediment removal on wetland C and N concentrations and determine subsequent C sequestration potential. We also were interested in determining the importance of the presence of wetlands on the landscape to C sequestration given the loss of wetlands that has occurred. We hypothesized that sediment removal might decrease C sequestration potential and that the presence of wetlands on the landscape provides important C sequestration sites. To accomplish these objectives we sampled 60 Playas and their immediate watersheds (20 each from reference condition, cropland, and restored through sediment removal) in 2013 and 2014 by coring soil/sediments (mollisols) to a depth of 50 cm. Restored Playas contained 29% lower C and N in the top 5 cm than in reference and cropland land uses. The C in the top 5 cm was also 36% higher in the wetland than in the watershed. There were no differences in C and N among land uses/landscape positions at depths >5 cm. However, because restored Playas had sediment removed, in some cases down to the clay pan of the historic playa soil surface, on an areal basis, restored Playas stored 21% more soil organic carbon (SOC) in deeper horizons (25–50 cm) than reference or cropland conditions. Overall, SOC was similar among restored, cropland and reference wetlands to a 50 cm depth, indicating that sediment removal does not have a negative effect on C sequestration potential. On average, SOC was 15% higher in Playas than in adjacent uplands, demonstrating the importance of playa wetlands on the landscape to C sequestration. Results of this study have widespread applicability because depressional wetlands are the dominant wetland type in temperate agroecosystems.
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soil organic carbon in Playas and adjacent prairies cropland and conservation reserve program land of the high plains usa
Soil & Tillage Research, 2016Co-Authors: Jessica L Oconnell, Scott T Mcmurry, Dale W Daniel, Loren M. SmithAbstract:Abstract Soil organic carbon (SOC) is an important reservoir for atmospheric CO2 associated with climate warming. The High Plains, USA, lacks region-wide SOC estimates within playa wetlands and their adjacent watershed. Croplands often have less SOC than grasslands, and the Conservation Reserve Program (CRP; former croplands planted to grass) may return SOC. Our goals were to estimate SOC within playa wetlands and investigate small scale differences within wetland catchments across a broad agriculturally modified landscape. We estimated SOC (kg m−2) to 50 cm depth from 4 soil cores/catchment (in Playas and 10, 40 and 100 m into uplands) at 56, 52, and 54 sites in native grassland, CRP and cropland, respectively. At a subset of sample locations within each land use type, we estimated SOC to 1 m depth to characterize SOC missed by shallow sampling. In playa wetlands, CRP SOC from 0 to 50 cm was 18% greater than croplands, but native grassland playa SOC did not differ from other land-uses. From 0 to 1 m, SOC in native grassland wetlands and uplands was 20% greater than the same habitats within croplands, while CRP lands were intermediate. Native grassland playa SOC also was 16% greater than in surrounding native short grass prairie. Playas therefore represent an important SOC repository in the High Plains ecoregion. CRP Playas and uplands may require an additional 10–30 years to resemble native grassland SOC. SOC increased with playa area throughout CRP and native grassland catchments, suggesting playa hydrogeomorphology influences adjacent upland SOC. High Plains Playas store 20.8 Tg C and cropland conversion caused a cumulative loss of 2.0 Tg C from 82,000 ha of Playas. Currently, CRP enrollment on over 25,000 ha of Playas has returned 0.2 Tg C (95% CI: 0.1–0.3), only half the historic SOC lost by cropland conversion within CRP Playas. To promote SOC storage, native grasslands and large Playas should be preserved and CRP enrollments should be maintained over long timescales.
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land use effects on sedimentation and water storage volume in Playas of the rainwater basin of nebraska
Land Use Policy, 2015Co-Authors: Dale W Daniel, Loren M. Smith, Scott T McmurryAbstract:A region dominated by cropland, the Rainwater Basin (RWB) of Nebraska, contains playa wetlands of international importance but estimates of historic wetland numbers suggest that approximately 90% of wetlands have been lost through draining and filling. To reverse these losses and restore their ecosystem services, >2000 ha of wetlands in the RWB have been enrolled into the US Department of Agriculture (USDA) Wetlands Reserve Program (WRP). Our goal was to compare water storage volume and sediment loads in RWB Playas in surrounding cropland, reference condition, and restored (WRP) land uses. To do so, we measured characteristics of 48 Playas that dictate water storage capabilities essential to their service provisioning (historic/current playa area, playa volume, and sediment depth to clay pan). Using historic wetland hydric soil footprints, we determined loss of historic area for wetlands in each land use type and using soil cores we estimated sediment depth and volume loss. Reference condition Playas had 380% more functional wetland area and 8 times more volume than cropland Playas, WRP Playas were intermediate between reference and cropland Playas. In addition, reference condition Playas had lost the least amount of historic area (65%) followed by WRP (70%) and cropland (83%). Though cropland Playas lost the greatest extent of historic wetland area, they had sediment depths (to Bt layer) similar to Playas embedded in reference and WRP, indicating that all Playas in the region have been impacted by watershed soil erosion. In order to increase the overall positive impact on wetland services provided by enrolling Playas into the WRP, conservation practitioners should remove sediments down to the Bt layer in enrolled wetlands in the RWB and protect the immediate watershed to prevent further erosion.
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physical loss and modification of southern great plains Playas
Journal of Environmental Management, 2012Co-Authors: Lacrecia A Johnson, Loren M. Smith, David A. Haukos, Scott T McmurryAbstract:Abstract Playas are the primary wetland system in the Southern Great Plains (SGP) of North America providing critical stopover habitats for migratory birds in the Western Hemisphere. Collectively, these wetlands form the keystone ecosystem in this region supporting biodiversity for North America and provide habitat for native plants and animals that are essential for maintenance of international biological diversity along with other local and regional ecological services. Large-scale landscape changes in this region, primarily as a result of agriculturally-based anthropogenic impacts, threaten Playas with functional loss and physical extinction. These impacts are not considered in current estimates of the number of extant functional Playas, leading to biased estimates by groups or agencies extrapolating research or monitoring results, conducting conservation planning, and modeling impacts of future climate change. Using a combination of stochastic and empirical data, we identified impacts to Playas and playa watersheds and quantified the extent and rate of these impacts relative to physical loss. Only 0.2% of Playas had no wetland or watershed modification and we conservatively estimate that 17% of Playas recently existing on the landscape no longer are represented by an apparent depression. With the inclusion of sediment volume estimates where ≥100% of the volume of original differentiated playa soil has been filled, 60% or 16,855 Playas have been physically lost from the SGP despite a continued presence of a depression. Data also show that small Playas are being lost more rapidly than larger ones; the average size (±SE) of extant Playas has increased from 7.5 ± 0.47 to 8.5 ± 0.55 ha. The reduced ecological condition of 95.3% of Playas remaining on the landscape exceeds historical predictions of a maximum 85% of Playas ever being modified. Given the results of this study these changes can now be accounted for, resulting in more informed management and conservation of Playas and bring awareness to the urgency of implementation of effective conservation measures for Playas and the species that depend on this keystone ecosystem.
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Influence of Local and Landscape Characteristics on Avian Richness and Density in Wet Playas of the Southern Great Plains, USA
Wetlands, 2012Co-Authors: Joszu Tsai, Loren M. Smith, Louise S Venne, Scott T Mcmurry, David A. HaukosAbstract:Playa wetlands (shallow, circular, depressional wetlands) in the Southern Great Plains are essential to the maintenance of regional biodiversity. However, the relative importance of habitat characteristics for maintaining avian species richness and density in Playas is unknown. We examined influences of local- and landscape-scale characteristics on avian communities in wet Playas. We conducted biweekly avian surveys on 80 Playas (40 Playas/year) from summer 2003 through spring 2005. Avian species richness was positively related to playa area and hydroperiod. More avian species and greater densities of birds were found at wetlands when water depths were intermediate (30–80 cm) during fall, winter and spring. Increased cultivation in playa watersheds increased total-, native-, and exotic-avian species richness. However, unsustainable sediment accumulation caused by cultivation can fill the playa basin and result in the loss of playa function, which will not benefit future bird populations. Landscape variables generally were less consistent with avian communities among seasons compared to local variables. Playas with greater numbers of other Playas within 1 and 10 km had lower bird densities than those with fewer surrounding Playas, likely due to the increase of habitat availability. Larger Playas within predominantly uncultivated watersheds, that have an intermediate water depth, longer hydroperiod (within a season), and 26–50% vegetation cover are likely to maximize seasonal native avian richness. However, manipulating static water depths and maintaining long hydroperiods over extended periods will not meet avian objectives over the long term because Playas must go through natural wet/dry fluctuations between years to maintain the desired plant community and productivity that supports diverse avian populations.
Jason J. Gurdak - One of the best experts on this subject based on the ideXlab platform.
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Review: Recharge rates and chemistry beneath Playas of the High Plains aquifer, USA
Hydrogeology Journal, 2010Co-Authors: Jason J. Gurdak, Cassia D. RoeAbstract:ResumenLas Playas son efímeras, humedales de cuencas cerradas que son supuestas como una importante fuente de recarga del acuífero de High Plains en el centro de EEUU. La naturaleza efímera de las Playas, los bajos ritmos de recarga regional, y una fuerte dependencia de las aguas subterráneas del acuífero de las High Plains ha impulsado muchas preguntas acerca de la contribución y calidad de la recarga desde las Playas al acuífero de High Plains. Como resultado, ha habido un considerable debate científico acerca del potencial del agua para infiltrar en los lechos relativamente impermeables de la playa, el tránsito a través de los sedimentos de la zona no saturada que tienen decenas de metros de espesor, y la subsecuente recarga del acuífero de High Plains. Esta revisión crítica examina los estudios previamente publicados sobre los procesos que controlan los ritmo de la recarga y química por debajo de las Playas. Los ritmos de recarga informados por debajo de las Playas oscilaron entre menos de 1.0 y más de 500 mm/año y son generalmente de 1 a 2 órdenes de magnitud más altos que el ritmo de la recarga debajo de la localización de la interplaya. La mayoría de los estudios apoyan el modelo conceptual que las Playas son importantes zonas de recarga al acuífero de High Plains y no son depresiones estrictamente evaporativos. Los principales hallazgos de esta revisión proveen implicancias científicas de base para el manejo de las Playas, de los recursos de agua subterránea en el acuífero de High Plains y direcciones para investigaciones futuras.RésuméLes Playas sont des bassins humides fermés éphémères supposés être une source importante de recharge de l’aquifère High Plains au centre des USA. La nature éphémère des Playas, des taux de recharge régionaux lents, et une forte dépendance de l’aquifère High Plains a suscité de nombreuses questions concernant la contribution et la qualité des Playas à la recharge l’aquifère High Plains. Par suite, un débat scientifique important a eu lieu sur le potentiel d’infiltration de l’eau dans les substrats relativement imperméables des Playas, écoulement à travers les sédiments de la zone non saturée épais de dizaines de mètres, et par suite recharge de l’aquifère High Plains. Cette étude critique examine les études antérieurement publiées sur le processus contrôlant les taux de recharge et la chimie sous les Playas. Les taux de recharge sous Playas s’échelonnent de moins de 1.0 à plus de 500 mm/an et sont généralement de 1 à 2 fois plus élevés que les taux de recharge sous les interPlayas. La plupart des études retiennent le modèle conceptuel faisant des Playas des zones importantes de recharge de l’aquifère High Plains et non de strictes surfaces d’évaporation. Les principaux résultats de cette étude sont des recommandations scientifiques concernant la gestion des Playas et des ressources en eau de l’aquifère High Plains et des axes de recherche future.ResumoAs Playas são efémeras, e correspondem a áreas húmidas temporárias associadas a bacias fechadas, que são hipoteticamente uma fonte importante de recarga para o aquífero dos High Plains, no centro dos EUA. A natureza efémera das Playas , as baixas taxas regionais de recarga, e a forte dependência da água subterrânea do aquífero dos High Plains, colocou muitas questões no que concerne à contribuição e qualidade da recarga a partir das Playas para esse aquífero. Como resultado, tem existido um debate científico considerável sobre o potencial de infiltração de água através das bases relativamente impermeáveis das Playas , da circulação através dos sedimentos da zona não saturada, com espessuras de dezenas de metros, e subsequente recarga do aquífero dos High Plains. Esta análise crítica examina estudos previamente publicados sobre o processo que controla as taxas de recarga e a química sob as Playas . Taxas de recarga reportadas sob as Playas variam desde menos de 1.0 a mais de 500 mm/ano e são geralmente 1 a 2 ordens de magnitude mais elevadas do que as taxas de recarga sob ambientes inter- playa . A maioria dos estudos suportam o modelo conceptual de que as zonas de Playas são importantes áreas de recarga para o aquífero dos High Plains e não são estritamente bacias de evaporação. As principais conclusões desta análise fornecem indicações baseadas na ciência para a gestão dos recursos hídricos subterrâneos e Playas do aquífero dos High Plains, e indicam direcções para pesquisas futuras.摘要普雷亚斯 (Playas) 是一种季节性、闭合盆地湿地, 被认为是美国中部高原含水层的重要补给源。该湿地的季节性特点、低区域补给速率, 及对来自于高原含水层中的地下水的强依赖性引发了许多问题, 包括其对补给高原含水层的贡献和水质。结果, 对于水能否通过湿地底部的相对隔水层, 穿过数十米厚的非饱和带沉积物, 最终补给到高原含水层出现了许多的学术争论。本文综述了已发表的有关控制湿地下补给速率和化学的过程的研究。报道的补给速率为不到1.0 至大于 500 mm/yr, 较通常的湿地间地块的补给速率高出1到2个数量级。大部分研究支持湿地为高原含水层的重要补给区, 且非严格的“蒸发皿”这一概念模型。本综述的主要发现为普雷亚斯湿地和高原含水层地下水资源的管理提供了科学依据, 并为未来的研究指明了方向。AbstractPlayas are ephemeral, closed-basin wetlands that are hypothesized as an important source of recharge to the High Plains aquifer in central USA. The ephemeral nature of Playas, low regional recharge rates, and a strong reliance on groundwater from the High Plains aquifer has prompted many questions regarding the contribution and quality of recharge from Playas to the High Plains aquifer. As a result, there has been considerable scientific debate about the potential for water to infiltrate the relatively impermeable playa floors, travel through the unsaturated zone sediments that are tens of meters thick, and subsequently recharge the High Plains aquifer. This critical review examines previously published studies on the processes that control recharge rates and chemistry beneath Playas. Reported recharge rates beneath Playas range from less than 1.0 to more than 500 mm/yr and are generally 1–2 orders of magnitude higher than recharge rates beneath interplaya settings. Most studies support the conceptual model that Playas are important zones of recharge to the High Plains aquifer and are not strictly evaporative pans. The major findings of this review provide science-based implications for management of Playas and groundwater resources of the High Plains aquifer and directions for future research.
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Review: Recharge rates and chemistry beneath Playas of the High Plains aquifer, USA
Hydrogeology Journal, 2010Co-Authors: Jason J. GurdakAbstract:As Playas são efémeras, e correspondem a áreas húmidas temporárias associadas a bacias fechadas, que são hipoteticamente uma fonte importante de recarga para o aquífero dos High Plains, no centro dos EUA. A natureza efémera das Playas , as baixas taxas regionais de recarga, e a forte dependência da água subterrânea do aquífero dos High Plains, colocou muitas questões no que concerne à contribuição e qualidade da recarga a partir das Playas para esse aquífero. Como resultado, tem existido um debate científico considerável sobre o potencial de infiltração de água através das bases relativamente impermeáveis das Playas , da circulação através dos sedimentos da zona não saturada, com espessuras de dezenas de metros, e subsequente recarga do aquífero dos High Plains. Esta análise crítica examina estudos previamente publicados sobre o processo que controla as taxas de recarga e a química sob as Playas . Taxas de recarga reportadas sob as Playas variam desde menos de 1.0 a mais de 500 mm/ano e são geralmente 1 a 2 ordens de magnitude mais elevadas do que as taxas de recarga sob ambientes inter- playa . A maioria dos estudos suportam o modelo conceptual de que as zonas de Playas são importantes áreas de recarga para o aquífero dos High Plains e não são estritamente bacias de evaporação. As principais conclusões desta análise fornecem indicações baseadas na ciência para a gestão dos recursos hídricos subterrâneos e Playas do aquífero dos High Plains, e indicam direcções para pesquisas futuras. 普雷亚斯 (Playas) 是一种季节性、闭合盆地湿地, 被认为是美国中部高原含水层的重要补给源。该湿地的季节性特点、低区域补给速率, 及对来自于高原含水层中的地下水的强依赖性引发了许多问题, 包括其对补给高原含水层的贡献和水质。结果, 对于水能否通过湿地底部的相对隔水层, 穿过数十米厚的非饱和带沉积物, 最终补给到高原含水层出现了许多的学术争论。本文综述了已发表的有关控制湿地下补给速率和化学的过程的研究。报道的补给速率为不到1.0 至大于 500 mm/yr, 较通常的湿地间地块的补给速率高出1到2个数量级。大部分研究支持湿地为高原含水层的重要补给区, 且非严格的“蒸发皿”这一概念模型。本综述的主要发现为普雷亚斯湿地和高原含水层地下水资源的管理提供了科学依据, 并为未来的研究指明了方向。 Las Playas son efímeras, humedales de cuencas cerradas que son supuestas como una importante fuente de recarga del acuífero de High Plains en el centro de EEUU. La naturaleza efímera de las Playas, los bajos ritmos de recarga regional, y una fuerte dependencia de las aguas subterráneas del acuífero de las High Plains ha impulsado muchas preguntas acerca de la contribución y calidad de la recarga desde las Playas al acuífero de High Plains. Como resultado, ha habido un considerable debate científico acerca del potencial del agua para infiltrar en los lechos relativamente impermeables de la playa, el tránsito a través de los sedimentos de la zona no saturada que tienen decenas de metros de espesor, y la subsecuente recarga del acuífero de High Plains. Esta revisión crítica examina los estudios previamente publicados sobre los procesos que controlan los ritmo de la recarga y química por debajo de las Playas. Los ritmos de recarga informados por debajo de las Playas oscilaron entre menos de 1.0 y más de 500 mm/año y son generalmente de 1 a 2 órdenes de magnitud más altos que el ritmo de la recarga debajo de la localización de la interplaya. La mayoría de los estudios apoyan el modelo conceptual que las Playas son importantes zonas de recarga al acuífero de High Plains y no son depresiones estrictamente evaporativos. Los principales hallazgos de esta revisión proveen implicancias científicas de base para el manejo de las Playas, de los recursos de agua subterránea en el acuífero de High Plains y direcciones para investigaciones futuras. Les Playas sont des bassins humides fermés éphémères supposés être une source importante de recharge de l’aquifère High Plains au centre des USA. La nature éphémère des Playas, des taux de recharge régionaux lents, et une forte dépendance de l’aquifère High Plains a suscité de nombreuses questions concernant la contribution et la qualité des Playas à la recharge l’aquifère High Plains. Par suite, un débat scientifique important a eu lieu sur le potentiel d’infiltration de l’eau dans les substrats relativement imperméables des Playas, écoulement à travers les sédiments de la zone non saturée épais de dizaines de mètres, et par suite recharge de l’aquifère High Plains. Cette étude critique examine les études antérieurement publiées sur le processus contrôlant les taux de recharge et la chimie sous les Playas. Les taux de recharge sous Playas s’échelonnent de moins de 1.0 à plus de 500 mm/an et sont généralement de 1 à 2 fois plus élevés que les taux de recharge sous les interPlayas. La plupart des études retiennent le modèle conceptuel faisant des Playas des zones importantes de recharge de l’aquifère High Plains et non de strictes surfaces d’évaporation. Les principaux résultats de cette étude sont des recommandations scientifiques concernant la gestion des Playas et des ressources en eau de l’aquifère High Plains et des axes de recherche future. Playas are ephemeral, closed-basin wetlands that are hypothesized as an important source of recharge to the High Plains aquifer in central USA. The ephemeral nature of Playas, low regional recharge rates, and a strong reliance on groundwater from the High Plains aquifer has prompted many questions regarding the contribution and quality of recharge from Playas to the High Plains aquifer. As a result, there has been considerable scientific debate about the potential for water to infiltrate the relatively impermeable playa floors, travel through the unsaturated zone sediments that are tens of meters thick, and subsequently recharge the High Plains aquifer. This critical review examines previously published studies on the processes that control recharge rates and chemistry beneath Playas. Reported recharge rates beneath Playas range from less than 1.0 to more than 500 mm/yr and are generally 1–2 orders of magnitude higher than recharge rates beneath interplaya settings. Most studies support the conceptual model that Playas are important zones of recharge to the High Plains aquifer and are not strictly evaporative pans. The major findings of this review provide science-based implications for management of Playas and groundwater resources of the High Plains aquifer and directions for future research.
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review recharge rates and chemistry beneath Playas of the high plains aquifer usa
Hydrogeology Journal, 2010Co-Authors: Jason J. GurdakAbstract:Playas are ephemeral, closed-basin wetlands that are hypothesized as an important source of recharge to the High Plains aquifer in central USA. The ephemeral nature of Playas, low regional recharge rates, and a strong reliance on groundwater from the High Plains aquifer has prompted many questions regarding the contribution and quality of recharge from Playas to the High Plains aquifer. As a result, there has been considerable scientific debate about the potential for water to infiltrate the relatively impermeable playa floors, travel through the unsaturated zone sediments that are tens of meters thick, and subsequently recharge the High Plains aquifer. This critical review examines previously published studies on the processes that control recharge rates and chemistry beneath Playas. Reported recharge rates beneath Playas range from less than 1.0 to more than 500 mm/yr and are generally 1–2 orders of magnitude higher than recharge rates beneath interplaya settings. Most studies support the conceptual model that Playas are important zones of recharge to the High Plains aquifer and are not strictly evaporative pans. The major findings of this review provide science-based implications for management of Playas and groundwater resources of the High Plains aquifer and directions for future research.
David A. Haukos - One of the best experts on this subject based on the ideXlab platform.
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physical loss and modification of southern great plains Playas
Journal of Environmental Management, 2012Co-Authors: Lacrecia A Johnson, Loren M. Smith, David A. Haukos, Scott T McmurryAbstract:Abstract Playas are the primary wetland system in the Southern Great Plains (SGP) of North America providing critical stopover habitats for migratory birds in the Western Hemisphere. Collectively, these wetlands form the keystone ecosystem in this region supporting biodiversity for North America and provide habitat for native plants and animals that are essential for maintenance of international biological diversity along with other local and regional ecological services. Large-scale landscape changes in this region, primarily as a result of agriculturally-based anthropogenic impacts, threaten Playas with functional loss and physical extinction. These impacts are not considered in current estimates of the number of extant functional Playas, leading to biased estimates by groups or agencies extrapolating research or monitoring results, conducting conservation planning, and modeling impacts of future climate change. Using a combination of stochastic and empirical data, we identified impacts to Playas and playa watersheds and quantified the extent and rate of these impacts relative to physical loss. Only 0.2% of Playas had no wetland or watershed modification and we conservatively estimate that 17% of Playas recently existing on the landscape no longer are represented by an apparent depression. With the inclusion of sediment volume estimates where ≥100% of the volume of original differentiated playa soil has been filled, 60% or 16,855 Playas have been physically lost from the SGP despite a continued presence of a depression. Data also show that small Playas are being lost more rapidly than larger ones; the average size (±SE) of extant Playas has increased from 7.5 ± 0.47 to 8.5 ± 0.55 ha. The reduced ecological condition of 95.3% of Playas remaining on the landscape exceeds historical predictions of a maximum 85% of Playas ever being modified. Given the results of this study these changes can now be accounted for, resulting in more informed management and conservation of Playas and bring awareness to the urgency of implementation of effective conservation measures for Playas and the species that depend on this keystone ecosystem.
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Influence of Local and Landscape Characteristics on Avian Richness and Density in Wet Playas of the Southern Great Plains, USA
Wetlands, 2012Co-Authors: Joszu Tsai, Loren M. Smith, Louise S Venne, Scott T Mcmurry, David A. HaukosAbstract:Playa wetlands (shallow, circular, depressional wetlands) in the Southern Great Plains are essential to the maintenance of regional biodiversity. However, the relative importance of habitat characteristics for maintaining avian species richness and density in Playas is unknown. We examined influences of local- and landscape-scale characteristics on avian communities in wet Playas. We conducted biweekly avian surveys on 80 Playas (40 Playas/year) from summer 2003 through spring 2005. Avian species richness was positively related to playa area and hydroperiod. More avian species and greater densities of birds were found at wetlands when water depths were intermediate (30–80 cm) during fall, winter and spring. Increased cultivation in playa watersheds increased total-, native-, and exotic-avian species richness. However, unsustainable sediment accumulation caused by cultivation can fill the playa basin and result in the loss of playa function, which will not benefit future bird populations. Landscape variables generally were less consistent with avian communities among seasons compared to local variables. Playas with greater numbers of other Playas within 1 and 10 km had lower bird densities than those with fewer surrounding Playas, likely due to the increase of habitat availability. Larger Playas within predominantly uncultivated watersheds, that have an intermediate water depth, longer hydroperiod (within a season), and 26–50% vegetation cover are likely to maximize seasonal native avian richness. However, manipulating static water depths and maintaining long hydroperiods over extended periods will not meet avian objectives over the long term because Playas must go through natural wet/dry fluctuations between years to maintain the desired plant community and productivity that supports diverse avian populations.
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ecosystem services provided by Playas in the high plains potential influences of usda conservation programs
Ecological Applications, 2011Co-Authors: Loren M. Smith, David A. Haukos, Scott T Mcmurry, Ted Lagrange, David B WillisAbstract:Playas are shallow depressional wetlands and the dominant wetland type in the non-glaciated High Plains of the United States. This region is one of the most intensively cultivated regions in the Western Hemisphere, and Playas are profoundly impacted by a variety of agricultural activities. Conservation practices promoted through Farm Bills by the U.S. Department of Agriculture (USDA) that influence Playas and surrounding catchments impact ecosystem functions and related services provided by wetlands in this region. As part of a national assessment, we review effects of agricultural cultivation and effectiveness of USDA conservation programs and practices on ecosystem functions and associated services of Playas. Services provided by Playas are influenced by hydrological function, and unlike other wetland types in the United States, hydrological function of Playas is impacted more by accumulated sediments than drainage. Most Playas with cultivated catchments have lost greater than 100% of their volume from sedimentation causing reduced hydroperiods. The Conservation Reserve Program (CRP) has the largest influence on playa catchments (the High Plains has >2.8 million ha), and associated sedimentation, of any USDA program. Unfortunately, most practices applied under CRP did not consider restoration of playa ecosystem function as a primary benefit, but rather established dense exotic grass in the watersheds to reduce soil erosion. Although this has reduced soil erosion, few studies have investigated its effects on playa hydrological function and services. Our review demonstrates that the Wetlands Reserve Program (WRP) has seldom been applied in the High Plains outside of south-central Nebraska. However, this is the primary program that exists within the USDA allowing conservation practices that restore wetland hydrology such as sediment removal. In addition to sediment removal, this practice has the greatest potential effect on improving hydrologic function by reducing sedimentation in vegetative buffer strips. We estimate that a 50-m native-grass buffer strip could improve individual playa hydroperiods by up to 90 days annually, enhancing delivery of most natural playa services. The potential for restoration of playa services using USDA programs is extensive, but only if WRP and associated practices are promoted and Playas are considered an integral part of CRP contracts.
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13.3.7. Ecology of Playa Lakes
2008Co-Authors: David A. Haukos, Loren M. SmithAbstract:Between 25,000 and 30,000 playa lakes are in the playa lakes region of the southern high plains (Fig. 1). Most Playas are in west Texas (about 20,000), and fewer, in New Mexico, Oklahoma, Kansas, and Colorado. The playa lakes region is one of the most intensively cultivated areas of North America. Dominant crops range from cotton in southern areas to cereal grains in the north. Therefore, most of the native short-grass prairie is gone, replaced by crops and, recently, grasses of the Conservation Reserve Program. Playas are the predominant wetlands and major wildlife habitat of the region. More than 115 bird species, including 20 species of waterfowl, and 10 mammal species have been documented in Playas. Waterfowl nest in the area, producing up to 250,000 ducklings in wetter years. Dominant breeding and nesting species are mallards and blue-winged teals. During the very protracted breeding season, birds hatch from April through August. Several million shorebirds and waterfowl migrate through the area each spring and fall. More than 400,000 sandhill cranes migrate through and winter in the region, concentrating primarily on the larger saline lakes in the southern portion of the playa lakes region. The primary importance of the playa lakes region to waterfowl is as a wintering area. Wintering waterfowl populations in the playa lakes region range from 1 to 3 million birds, depending on fall precipitation patterns that determine the number of flooded Playas. The most common wintering ducks are mallards, northern pintails, green-winged teals, and American wigeons. About 500,000 Canada geese and 100,000 lesser snow geese winter in the playa lakes region, and numbers of geese have increased annually since the early 1980’s. This chapter describes the physiography and ecology of playa lakes and their attributes that benefit waterfowl.
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Floral Diversity in Relation to Playa Wetland Area and Watershed Disturbance
Conservation Biology, 2002Co-Authors: Loren M. Smith, David A. HaukosAbstract:There are 25,000-30,000 playa wetlands in the intensively cultivated Southern Great Plains of the United States. Knowledge of area and watershed influences on wetland flora are needed to guide their conser- vation. We surveyed plant-community composition in 224 Playas over 360,000 km 2 and examined the rela- tionships of species richness and diversity (Shannon's) to playa area and watershed disturbance. The rela- tionship of increasing species diversity to increasing area is most often hypothesized to be associated with an increasing number of habitats and/or larger populations as area increases. Watershed disturbance ( peren- nial grassland vs. annual cropland) was included to determine its relationship to floral diversity and bioin- vasion by exotic species. For all (terrestrial and wetland) plant species and all Playas, there were only mar- ginal relationships ( r 2 � 0.1) between area and richness and diversity. Analyses supported the hypothesis that the number of habitats affects playa plant diversity because number of habitats changed little as playa area increased. Tests on only wetland plant species suggested stronger ( r 2 � 0.2) relationships between rich- ness and area. This relationship also was not likely related to increased population size, because large Playas remain flooded longer than small Playas, and therefore wetland plant species have a greater opportunity to become established. Finally, Playas with cropland watersheds had more ( p � 0.05) exotic species, higher di- versity, and fewer perennial species than Playas with grassland watersheds. Because watershed cultivation has altered playa hydroperiod and increased frequency of disturbance, Playas are associated with a flora dominated more by annuals and exotics. Conservation efforts aimed at preserving playa wetland plant diver- sity and native communities should focus not only on the area of the wetland but also on the condition of its watershed.
Vance T Holliday - One of the best experts on this subject based on the ideXlab platform.
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late quaternary sedimentology and geochronology of small Playas on the southern high plains texas and new mexico u s a
Quaternary Research, 2008Co-Authors: Vance T Holliday, James H Mayer, Glen G FredlundAbstract:Abstract Playas are small, circular basins forming a ubiquitous component of the southern High Plains landscape. They are filled with carbonaceous mud deposited since the terminal Pleistocene. The stratigraphy and geochronology of 30 Playas was investigated to better understand the paleoenvironmental record of basin filling. At the base of the fill in some Playas is a well sorted eolian sand dated between ~ 13,000 and ~ 11,000 14C yr BP. The beginning of mud deposition, representing aggradation of eolian dust on a moist, vegetated playa floor was largely between ~ 12,000 and ~ 10,500 14C yr BP. Playa filling slowed ~ 9000 to ~ 4000 14C yr BP, probably due to dry conditions, increased ~ 4000 to ~ 2000 14C yr BP, then slowed again. Eolian sand and loam, likely representing regional aridity, accumulated in some basins episodically just prior to ~ 10,700 14C yr BP, between ~ 8600 and ~ 4700 14C yr BP, and at ~ 1300 14C yr BP. Stable C isotopes from one basin indicate that the playa was inundated only seasonally throughout the record beginning ~ 11,500 14C yr BP. The phytolith record in that basin indicates an abrupt shift toward cooling ~ 11,400 to ~ 11,200 14C yr BP and then increasing importance of xeric-adapted C4 grasses through the Holocene.
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Playas and lunettes on the southern high plains morphometric and spatial relationships
Annals of The Association of American Geographers, 1995Co-Authors: Ty J Sabin, Vance T HollidayAbstract:Abstract The surface of the Southern High Plains is dotted with thousands of small (<5 km2), circular, seasonally dry depressions, or Playas, some of which are accompanied by a crescentic dune ridge, or lunette. The plays are inset into the sheets of eolian sediment that blanket the region (Blackwater Draw Formation) and the lunettes rest on the eolian mantle. Approximately 25,000 small Playas, 1,100 of which have a lunette, were counted from all 540 topographic quadrangles covering the region (verified using data from soil surveys). Statistical analyses of the physical and spatial relationships of Playas and lunettes were undertaken to better understand the origins and development of Playas, and their relationship to lunettes. Data were collected from a subset of 40 topographic maps, digitized on a GIS, and analyzed using a nonparametric statistical procedure. Variation in texture of the Blackwater Draw Formation exerts considerable control on the distribution and size of Playas. Playas are most numerous...