Rainwater Basin Research Articles

Combining Multi-View UAV Photogrammetry, Thermal Imaging, and Computer Vision Can Derive Cost-Effective Ecological Indicators for Habitat Assessment

Recent developments in Unmanned Aircraft Vehicles (UAVs), thermal imaging, and Auto-machine learning (AutoML) have shown high potential for precise wildlife surveys but have rarely been studied for habitat assessment. Here, we propose a framework that leverages these advanced techniques to achieve cost-effective habitat quality assessment from the perspective of actual wildlife community usage. The framework exploits vision intelligence hidden in the UAV thermal images and AutoML methods to achieve cost-effective wildlife distribution mapping, and then derives wildlife use indicators to imply habitat quality variance. We conducted UAV-based thermal wildlife surveys at three wetlands in the Rainwater Basin, Nebraska. Experiments were set to examine the optimal protocols, including various flight designs (61 and 122 m), feature types, and AutoML. The results showed that UAV images collected at 61 m with a spatial resolution of 7.5 cm, combined with Faster R-CNN, returned the optimal wildlife mapping (more than 90% accuracy). Results also indicated that the vision intelligence exploited can effectively transfer the redundant AutoML adaptation cycles into a fully automatic process (with around 33 times efficiency improvement for data labeling), facilitating cost-effective AutoML adaptation. Eventually, the derived ecological indicators can explain the wildlife use status well, reflecting potential within- and between-habitat quality variance.

Relating weather radar data to migrating waterfowl abundance in the Rainwater Basin of Nebraska

AbstractWaterfowl migrations are large‐scale events that involve millions of birds moving over broad geographic extents, which make them difficult to quantify and study. Historically, wildlife managers have relied mostly on field surveys, such as visual counts from the ground or air that sample at small spatial or temporal extents, or both. Combining field surveys with remote sensing data comprehensively collected over large spatial extents at high temporal frequency may improve the study of migrating waterfowl distributions. We tested the strength of the relationship between broad‐scale weather surveillance radar data and fine‐scale field surveys of waterfowl abundance at wetlands within the Rainwater Basin of Nebraska, USA, from 2017–2019. Radar reflectivity of waterfowl at the peak exodus of evening flights was positively correlated with diurnal waterfowl count data, although there was unexplained variation in the relationship. The association was also very similar across various time scales ranging from daily to monthly averages of waterfowl abundance. We suggest that human‐based ground surveys can calibrate and leverage more comprehensive remote sensing data to get a broad understanding of waterfowl distributions during migration. Several confounding factors, such as spatial displacement between radar and survey observation, individual variation in orientation and body size, and identification of avian species sampled by radar, remain on the path to improving radar‐based waterfowl estimates.

Khargia gen. nov., a new genus of simple trichal Cyanobacteria from the Persian Gulf

Information regarding the diversity of Cyanobacteria in many parts of the world is still minimal. One example of a region that has not yet been widely studied is south-western Asia, including the region of the Persian Gulf. A culture-dependent study of cyanobacterial diversity in a rainwater basin on Kharg Island enabled the isolation of a novel taxon, previously unnamed, from a simple trichal cyanobacterium. Further comparisons showed the existence of closely related strains/taxa from other parts of the world, namely the strains CCALA 945 isolated from South Italy and "<i>Leptolyngbya india" </i>from India. Herein, we have thus described the new genus <i>Khargia</i> and the new species <i>Khargia iranica. </i>Other strains, isolated by other authors, were included in the <i>Khargia</i> genus as additional species: <i>Khargia italica</i> and <i>Khargia indica</i>. The recognition of the new genus was based on morphological evaluations (identification by both light and electron microscopy), the phylogenetic analyses based on the 16S rRNA gene, and species delimitation based on Automatic Barcode Gap Definition (ABGD), Generalized Mixed Yule Coalescent (GMYC), bayesian version of Poisson Tree Processes (bPTP), and the secondary structure of 16S-23S rRNA ITS region of the studied strains.

A Tale of Two Complexes: Secretive Marsh Bird Abundance Differs in the Sandhills and Rainwater Basin, Nebraska

A Tale of Two Complexes: Secretive Marsh Bird Abundance Differs in the Sandhills and Rainwater Basin, Nebraska

Utilizing unsupervised learning, multi-view imaging, and CNN-based attention facilitates cost-effective wetland mapping

The combination of Unmanned/Unoccupied Aerial Vehicle (UAV) data and deep learning, especially convolutional neural networks (CNNs), offers robust new tools for precision land cover mapping. However, its successful application is highly dependent on local experiences that are rarely documented, resulting in practical limitations during implementation. Cost-effective deep learning frameworks for fast deployment are required. This study presents a deep learning adaptation framework, named Auto-UNet++, trying to streamline wetland mapping tasks (including training data labeling and organizing). The framework treats mapping tasks as an intact semantic segmentation pipeline and then integrates automatic strategies into each step to reduce human intervention. These automatic strategies are achieved by standard computer vision techniques, including multi-view (MV) imaging—highly overlapped UAV images over an area (for labeling/voting), unsupervised clustering (for labeling), multi-scale CNN (for feature extraction), and attention mechanism—a CNN design used to select informative features from input (for feature exploration/selection). The framework was tested on playa wetland mapping in the Rainwater Basin, Nebraska, USA, with multispectral UAV datasets. Generally, the multi-scale CNN mapping task achieved a high of 87% overall accuracy and over 90% accuracy in water delineation. The results indicate that the multi-view and attention strategies have the potential to improve segmentation performance, and together with unsupervised learning, save considerable labor/expertise. Interestingly, evidence shows that the band/scale attention (weight) is adaptively associated with the land cover percentages per input image, indicating spatial contexts captured. This finding highlights the potential usages of the attention rule in automatic feature exploration, selection, and model interpretation. The framework illustrating a highly automated deep learning deployment on small MV datasets facilitates cost-effective wetland cover mapping. Although limitations exist, the study demonstrated the possibility of where/how conventional segmentation pipelines can be improved in typical UAV wetland mapping tasks. The framework and findings are useful for similar applications (including non-UAV studies) that only have limited time, labor, and expertise to implement sophisticated semantic segmentation models.

A grain-size correction for metal pollution indexes in river sediments

According to the List of Hazardous Substances of the Agency of the Toxic Substances and Disease Registry (ATSDR 2017), some metallic elements such as Pb or Cd are still considered as the most polluting elements in the world. These elements accumulate in sediments, and there are various methods available that differentiate lithogenic sources from anthropogenic sources. For that, the natural geochemical background is required, however, its definition is far from unanimous: it can be a global or local value, single or statistically estimated value, depending on the studies. Our study is focused on the Subaé River in the state of Bahia, Northeastern Brazil, which was historically contaminated by lead metallurgy. The river sediments were sampled at 21 locations: one at the discharge point of the plant's rainwater basin, ten upstream, and ten downstream. The total contents of Fe, Ti, Mn, Pb, Zn, Cu, Cr, particle-size distribution, and organic matter were analyzed. The conventional geochemical indexes, i.e., the pollution degree (mCd), pollution load index, and enrichment factor indicated contamination by Zn, Pb, Cr, and Cu. Then, a new enrichment factor is introduced, assuming that the sediments come from erosion of soils in the watershed. After obtaining the natural concentrations of metals in the clay, silt, and sand fractions of uncontaminated reference soils, we corrected the pollution indexes by calculating a new individual background in each sediment sample, according to its grain size distribution. This new approach provided more precise indexes in the assessment of sediment pollution, by highlighting higher contamination of Zn and Pb (around 50%) and at the same time the absence of Cr and Cu contamination, two metals not involved with the metallurgical activity.

Effects of Wetland Presence and Upland Land Use on Wild Hymenopteran and Dipteran Pollinators in the Rainwater Basin of Nebraska, USA

Pollination is an ecosystem service that is in jeopardy globally. Decreasing trends in wild pollinator populations are primarily attributed to habitat loss and degradation. These concerns are especially apparent in the Rainwater Basin of Nebraska, USA where more than 90% of the land has been cultivated and 90% of the wetlands have been lost. We compared hymenopteran and dipteran pollinator abundance, richness, and diversity in 28 wetlands and their adjacent uplands within 3 dominant land-condition types: cropped, restored, and reference state. We used vane traps to capture local pollinator insects and sweep nets to collect insect pollinators on flowers. Vane-trap captures revealed a greater abundance, richness, and diversity of hymenopteran pollinators in uplands as compared to wetlands over the entire growing season in all land-condition types. However, net collections showed that hymenopterans foraged more in wetlands than in uplands, especially in restored wetlands. The exception was September when hymenopterans were captured in uplands more than wetlands while feeding on late season forbs. Dipteran vane-trap and sweep-net captures primarily consisted of hoverflies (Syrphidae). Hoverflies were more abundant in wetlands than uplands. All pollinators used both wetlands and uplands for resources. Thus, insect-pollinator conservation can be enhanced by promoting native forb communities and pollinator habitat through wetland restoration and the planting of buffer strips.

Future losses of playa wetlands decrease network structure and connectivity of the Rainwater Basin, Nebraska

The Rainwater Basin in south-central Nebraska once supported a complex network of ~ 12,000 spatially-isolated playa wetlands, but ~ 90% have been lost since European settlement. Future losses are likely and expected reductions in connectivity could further isolate populations, increasing local extinction rates of many wetland species. However, to what extent future losses will affect wildlife likely depends on the role of lost wetlands in maintaining connectivity. We compared the current Rainwater Basin network to future wetland loss scenarios to assess minimum, mean, and maximum effects of losses on network connectivity for a range of wildlife taxa. We used network models to rank wetlands by their functionality and relative importance in maintaining connectivity. We then removed 10–50% of high-ranked, low-ranked, or random subsets of wetlands and assessed connectivity of the remaining network. A 10% loss of highly-ranked wetlands substantially decreased connectivity for species with dispersal capabilities < 5.5 km, while a 40–50% loss reduced connectivity for all tested dispersal distances (0.5–12.0 km). When large proportions of highly-ranked wetlands were lost, the eastern and western halves of the Rainwater Basin network were no longer connected for any dispersal distance. Loss of low-ranked wetlands had minimal effects on network connectivity, until at least the lowest-ranked 50% were removed. Many highly-ranked playa wetlands in the Rainwater Basin are currently unprotected and might disappear from the landscape. Protecting wetlands that are key in maintaining connectivity especially benefits species with limited dispersal capabilities (< 5.5 km) for which consequences of future habitat losses might be worst.

Conservation significantly improves wetland conditions: evaluation of playa wetlands in different conservation status

This study assessed the conditions of wetland hydrology, hydrophyte and soil under different state and federal conservation programs, and then identified the restorable potential of conserved playas. The distribution of hydrology and hydrophyte were geospatially examined through annual tracking the quantity and quality of wetlands on historical hydric soil footprints under different conservation programs in the Rainwater Basin in Nebraska, USA during 2004–2015. The results show that the historical hydric soil footprints with the conservation programs had significantly better performance in ponded water and hydrophyte than non-conserved wetlands. The yearly average of ponded water areas within footprints varies at 12.59% for the Waterfowl Production Areas (WPAs), 14.78% for Wildlife Management Areas (WMAs), 27.37% for Wetlands Reserve Program’s conservation easements (WRPs), and 1.86% for non-conserved wetlands, respectively. The yearly average of hydrophyte plant community coverage within footprints reaches at 77.51% for WPAs, 79.28% for WMAs, and 66.53% for WRPs, and 8.82% for non-conserved hydric footprints. Within conserved lands, Massie/Water soil series demonstrated the prominent ability to hold ponding water, especially in the ponded footprints with higher ponding frequency. Nevertheless, the proportion of Fillmore, Rusco or Butler soil series roughly decreased when the ponding water frequency increased. The areas, with high likelihood to be restored, are the places between annual ponding/hydrophyte covered areas and 11 years’ maximized ponding/hydrophyte areas.

Neonicotinoid insecticide concentrations in agricultural wetlands and associations with aquatic invertebrate communities

Neonicotinoids are considered a superior insecticide for agricultural pest management, although their impacts on non-target insects is a rising concern. Aside from laboratory and mesocosm studies, limited research has been directed towards the role neonicotinoids may have in structuring aquatic invertebrate communities in field settings. Therefore, we simultaneously collected aquatic invertebrate and surface water samples from 26 wetlands within a highly modified agricultural landscape of Nebraska’s Rainwater Basin during spring 2015. Water samples were tested for six different neonicotinoids, nutrients, and physical properties. Trace levels of clothianidin and imidacloprid were the only neonicotinoids detected, occurring in 85% and 15%, respectively, of wetlands sampled. All measurements for clothianidin and imidacloprid were below chronic toxicity benchmarks set by the United States Environmental Protection Agency. Neonicotinoid concentrations were significantly lower (W26, 0.05 = 42.5) at wetlands with vegetative buffer strips >50 m wide compared to wetlands with vegetative buffers strips <50 m. Although neonicotinoids were below benchmark concentrations proposed by government regulations, a significant negative association between neonicotinoid concentrations and aquatic invertebrate biomass was observed across all wetlands studied (Parameter Estimate = -0.031; SE = 0.014).

Using the electromagnetic induction survey method to examine the depth to clay soil layer (Bt horizon) in playa wetlands

PurposeSediment accumulation has been and continues to be a significant threat to the integrity of the playa wetland ecosystem. The purpose of this study was to determine the vertical depth to the clay soil layer (Bt horizon) and thus to calculate the thickness of sediments accumulated in playa wetlands.Materials and methodsThis study used the electromagnetic induction (EMI) survey method, specifically EM38-MK2 equipment, to measure the vertical depth to the clay soil layer at the publicly managed wetlands in the Rainwater Basin, Nebraska, USA.Results and discussionThe results indicated that the depth to the clay soil layer ranges from 21 to 78 cm (n = 279) with a mean sediment thickness of 39 cm. The annual sediment deposition rate since human settlement in the 1860s was calculated to be 0.26 cm year−1. The results provided science-based data to support future wetland restoration planning and the development of decision support tools that prioritize conservation delivery efforts.ConclusionsOur research confirmed that the EMI technique is effective and efficient at determining the depth to the Bt horizon for playa wetlands. Additionally, these results supported previous studies and continue to indicate that a large amount of sediment has accrued in these playa wetlands within the Rainwater Basin area since settlement. Wetland restoration ecologists can use this information to prioritize future wetland restoration work that intends to remove culturally accumulated sediments above the clay soil layer. These findings provided a contemporary summary of wetland soil profile information that is typically used to develop restoration plans. This research also filled the critical knowledge gap about the thickness of the upper soils and the depth to Bt in publicly managed wetlands.

Effects of Land Use on Greenhouse Gas Flux in Playa Wetlands and Associated Watersheds in the High Plains, USA

In the High Plains, U.S., native prairie conversion to cropland agriculture has resulted in a loss of service delivery capabilities from most depressional wetlands as a result of sedimentation. Restoring historic hydrological conditions to affected wetlands may rejuvenate some services, however, there may be tradeoffs due to emissions of CH4 and N2O. We evaluated the influence of two predominant conservation programs (Wetlands Reserve Program, WRP and Conservation Reserve Program, CRP) on gas emissions (CO2, CH4, N2O) from 42 playas and uplands in the High Plains of Nebraska. Because playa restoration through the WRP is most prevalent in the Rainwater Basin (RWB), we studied 27 playas/uplands among reference condition, cropland, and WRP land uses. We studied 15 playas/uplands within native grassland, cropland, and CRP land uses in the Western High Plains (WHP) of Nebraska. Emissions were collected bi-weekly from April-October of 2012 and 2013 from four landscape positions extending outward from the wetland center into upland. In RWB playas, CH4 and N2O emissions were similar among land uses but CO2 was 28% higher in cropland than WRP wetlands. Cropland uplands emitted 648% more N2O than reference and WRP uplands. Overall, net CO2-equiv emissions were lower in playas/uplands in WRP, suggesting that benefits of playa restoration may include climate mitigation services as well as increased water storage capacity and biodiversity provisioning. In the WHP, cropland and grassland playas emitted 46 and 23 times more CH4, respectively, than CRP in 2013. Playas in CRP emitted 43% less N2O than cropland playas. In 2013, net emissions for cropland and native grassland playas were 75% and 39% greater, respectively, than CRP playas. In the WHP, the benefits of lower gas emissions must be appropriately weighted against tradeoffs of ecosystem services related to shorter hydroperiods as a result of reduced runoff into playas in CRP.

Impacts of cattle grazing on seed production in Rainwater Basin Wetlands

The Rainwater Basin region of Nebraska is a critical stopover area for spring migrating waterfowl. Management concerns focus on producing sufficient wetland seed to meet the needs of these waterfowl. Cattle grazing is commonly used both alone and in combination with other management techniques to reduce invasive species such reed canarygrass that suppress seed production, but it was unknown what effect the grazing has on seed production, and how that effect might differ by vegetation type. This project examined the impact that different durations of grazing had on seed production in three sites containing both moist-soil and reed canarygrass dominated areas. We also examined the magnitude of the effect that grazing had on reducing reed canarygrass biomass with differing durations of grazing. The results suggest that cattle grazing impacts seed production differently in moist-soil and reed canarygrass dominated areas. Grazing decreases seed production in moist-soil areas, and longer grazing results in a greater decrease. In contrast, the highest seed production in reed canarygrass dominated areas was in areas grazed until July 15, and the lowest seed production was in areas grazed until September 15. The relationship between grazing and seed production in reed canarygrass areas is complex, but seed production in reed canarygrass areas was universally lower than in moist-soil vegetation at all grazing durations.

Effects of large-scale wetland loss on network connectivity of the Rainwater Basin, Nebraska

The Rainwater Basin region in south-central Nebraska supports a complex network of spatially-isolated wetlands that harbor diverse floral and faunal communities. Since European settlement, many wetlands have been lost from the network, which has increased distances among remaining wetlands. As a result, populations of wildlife species with limited dispersal capabilities may have become isolated and face greater local extinction risks. We compared the pre-European settlement and current extent of the Rainwater Basin network to assess the effects of wetland losses on network connectivity for a range of maximum dispersal distances. We constructed network models for a range of maximum dispersal distances and calculated network metrics to assess changes in network connectivity and the relative importance of individual wetlands in regulating flow. Since European settlement, the number of wetlands in the Rainwater Basin has decreased by > 90%. The average distance to the nearest neighboring wetland has increased by 150% to ~ 1.2 km, and the dispersal distance necessary to travel throughout the whole network has increased from 3.5 to 10.0 km. Last, relative importance of individual wetlands depended on the maximum dispersal distance. Which wetlands to preserve to maintain connectivity might therefore depend on the dispersal capabilities of the species or taxa of interest. To preserve a broad range of biodiversity, conservation efforts should focus on preserving dense clusters of wetlands at fine spatial scales to maintain current levels of network connectivity, and restoring connections between clusters to facilitate long-range dispersal of species with limited dispersal capabilities.

Are Waterfowl Food Resources Limited during Spring Migration? A Bioenergetic Assessment of Playas in Nebraska\u2019s Rainwater Basin

Accurate bioenergetic carrying capacity estimates of wetlands on public and private lands, as well as those managed for crop production are important for managing waterfowl populations and habitats. Given the importance of wetlands in the Rainwater Basin region of Nebraska for spring migrating waterfowl, we quantified and compared seed and aquatic invertebrate biomass and true metabolizable energy (TME) at three wetland types; public wetlands, wetlands enrolled in the Wetlands Reserve Program (WRP), and cropped wetlands. Median seed biomass estimates at public, WRP, and cropped wetlands were 593 kg/ha, 561 kg/ha, and 419 kg/ha respectively. Cumulative TME varied among wetland type, with greater TME at cropped wetlands (2431 kcal/kg) than public (1740 kcal/kg) and WRP wetlands (1781 kcal/kg). Seed biomass estimates from this study were statistically greater than those currently used for management planning in the RWB, however, TME estimates were statistically lower than estimates currently assumed for WRP and public wetlands. Our estimates for aquatic invertebrate biomass were approximately 40-fold less than seed biomass estimates. Based on spring ponding frequency at wetlands in Nebraska’s Rainwater Basin, and the caloric estimates derived for each wetland type, we concluded that the regions wetlands meet the energetic demand of spring migrating waterfowl during 10% of years.

Timing and Protocols for Estimating Seed Production in Moist-Soil and Phalaris arundinacea Dominated Areas in Rainwater Basin Wetlands

In the Rainwater Basin region of Nebraska, seeds produced by wetland plants are an important food source for waterfowl. Seed production estimates are used to set habitat management goals and evaluate management efforts. Most seed production estimates focus on one-time sampling during peak seed production, but it is unknown how well this captures the total production of wetland seeds throughout the growing season. We evaluated seed production from throughout the growing season in Rainwater Basin wetlands to describe timing of seed production, compare seed production estimates based on one-time and season-long sampling, and quantify how seed production is affected by the invasive species Phalaris arundinacea. Mature seeds were collected from early June to mid-October. One-time sampling of seed production in moist-soil vegetation estimates were only 27% that of season-long sampling. Estimates were consistently lower in P. arundinacea invaded areas. Season-long estimates in P. arundinacea areas were 19% those in moist-soil vegetation, and one-time sampling estimates were 10% those of moist-soil vegetation. We recommend that future seed production estimates use 2-3 sampling periods to better capture the full production of an area. Sampling periods should be based on the peak seed production of the most productive species in the targeted wetland.

Examining Playa Wetland Contemporary Conditions in the Rainwater Basin, Nebraska

Based on three critical criteria – soil, hydrology, and vegetation, this study examined contemporary playa wetland conditions to determine the extent of wetland degradation in the Rainwater Basin in south-central Nebraska. Geospatial statistics were used to evaluate the changes between historical hydric soil footprints and the most recent wetland survey datasets. The results indicate that the historical hydric soil footprints dominated by the Scott and Fillmore soil series have degraded 31.0% and 79.4% respectively. We also found approximately two-thirds of the footprints no longer pond water during spring migration. In fact, only 16.8% of the historical hydric soil footprints contain hydrophytes in recent surveys. Furthermore, the majority of these footprints (and the associated uplands) have been converted to cropland and no longer pond frequently or support hydrophytes. Additionally, the extensive grid road system supports commodity crop production, but in many instances this infrastructure has significantly altered wetland footprints and the associated watersheds to reduce the total water volume delivered to wetlands. The resulting situation is that conserved lands, including Waterfowl Production Areas (WPAs), Wildlife Management Areas (WMAs), and conservation easements only represent 11.3% of total historical footprints, but contribute to over 40.5% of the current total ponded water and hydrophytes.

The Effect of In-Field Rain Water Harvesting on Orange-Fleshed Sweet Potato Biomass and Yield

Water scarcity affects both food security and human nutrition. In-field rain water harvesting (IRWH) combines the advantages of rainwater harvesting, no-till, basin tillage and mulching on high drought risk clay soils. In this study, the IRWH system was customized to fit the cropping system of orange-fleshed sweet potato (OFSP). Field trials were conducted over two seasons to compare cultivation of OFSP using IRWH versus conventional tillage (CON). Data collection included plant survival, root initiation, marketable root yield, unmarketable root yield classes and biomass. Planting OFSP using the IRWH system resulted in significantly higher total biomass, higher marketable and total root yield per plant, as well as larger number of roots per plant compared to CON. Despite the relatively higher yield, total production (t/ha) was only significantly higher in season two at 4.6 t/ha vs 2.7 t/ha for CON. Subsistence farmers and households in semi-arid areas may grow small plots of orange-fleshed sweet potato in IRWH opposed to only growing maize and in that way add vitamin A to the diet. This is the first study on the application of IRWH to produce OFSP under rainfed conditions, and more research can be conducted to expand the knowledge on application and benefits of IRWH for OFSP production.

Effects of sediment removal and surrounding land use on carbon and nitrogen storage in playas and watersheds in the Rainwater Basin region of Nebraska

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 50cm. Restored playas contained 29% lower C and N in the top 5cm than in reference and cropland land uses. The C in the top 5cm 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 >5cm. 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 (25–50cm) than reference or cropland conditions. Overall, SOC was similar among restored, cropland and reference wetlands to a 50cm 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.

Shorebird stopover habitat decisions in a changing landscape

ABSTRACTTo examine how habitat use by sandpipers (Calidrisspp.; Baird's sandpipers, dunlin, least sandpipers, pectoral sandpipers, semipalmated sandpipers, stilt sandpipers, and white‐rumped sandpipers) varies across a broad suite of environmental conditions, we conducted surveys at wetlands throughout the spring migratory period in 2013 and 2014 in 2 important stopover regions: the Rainwater Basin (RWB) in Nebraska, USA, and the Prairie Pothole Region (PPR) in South Dakota, USA. Because providing adequate energetic resources for migratory birds is a high priority for wetland management, we also measured invertebrate abundance at managed wetlands in the RWB to determine how food abundance influences the occupancy and abundance of sandpipers on wetlands throughout the migratory period. To quantify habitat use, we surveyed wetlands every 7–10 days in both regions and visually estimated wetland attributes. Our results indicate that invertebrate abundance predicted occupancy, but not abundance, of sandpipers at wetlands in the RWB. The wetland vegetation characteristics that predict sandpiper occupancy are similar in both regions, but wetlands in the PPR support a higher abundance of sandpipers than wetlands in the RWB. Our results suggest that sandpipers make stopover decisions that balance local and regional wetland conditions. Managers should maintain the cues (i.e., mudflat) and ecological conditions beyond invertebrate abundance that predict sandpiper habitat use to successfully provide resources for sandpipers during migratory stopover if that is a goal of wetland management. © 2017 The Wildlife Society.