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At least 379 records · Page 21Linked to original sources

USGS2018

A review of Bayesian belief network models as decision-support tools for wetland conservation: Are water birds potential umbrella taxa?

Creative approaches to identifying umbrella species hold promise for devising effective surrogates of ecological communities or ecosystems. However, mechanistic niche models that predict range or habitat overlap among species may yet lack development. We reviewed literature on taxon-centered Bayesian belief network (BBN) models to explore a novel approach to identify umbrella taxa identifying taxonomic groups that share the largest proportion of habitat requirements (i.e., states of important habitat variables) with other wetland-dependent taxa. We reviewed and compiled published literature to provide a comprehensive and reproducible account of the current understanding of habitat requirements for freshwater, wetland-dependent taxa using BBNs. We found that wetland birds had the highest degree of shared habitat requirements with other taxa, and consequently may be suitable umbrella taxa in freshwater wetlands. Comparing habitat requirements using a BBN approach to build species distribution models, this review also identified taxa that may not benefit from conservation actions targeted at umbrella taxa by identifying taxa with unique habitat requirements not shared with umbrellas. Using a standard node set that accurately and comprehensively represents the ecosystem in question, BBNs could be designed to improve identification of umbrella taxa. In wetlands, expert knowledge about hydrology, geomorphology and soils could add important information regarding physical landscape characteristics relevant to species. Thus, a systems-oriented framework may improve overarching inferences from BBNs and subsequent utility to conservation planning and management.

Biological Conservation↗

USGS2022

Data sources and methods for digital mapping of eight valley-fill aquifer systems in upstate New York

Digital hydrogeologic maps were developed in eight study areas in upstate New York by the U.S. Geological Survey in cooperation with the New York State Department of Environmental Conservation. The digital maps define the hydrogeologic framework of the valley-fill aquifers and surrounding till-covered uplands in the vicinity of the villages of Ellenville and Wurtsboro and hamlets of Woodbourne and South Fallsburg in Sullivan and Ulster Counties, town of Greene in Chenango County, city of Cortland and town of Cincinnatus in Cortland County, city of Jamestown in Chautauqua County, city of Olean and village of Ellicottville in Cattaraugus County, and villages of Fishkill and Wappinger Falls in Dutchess County. The hydrogeologic framework provided the foundation for groundwater-flow models that were used in the delineation of areas contributing groundwater flow to production wells screened in four of the eight valley-fill aquifers considered in this study. The hydrogeologic framework for the other four study areas was developed for potential future use in groundwater contributing-area studies. Data used in the creation of all digital surfaces and thicknesses included published surficial geology; aquifer maps and hydrogeologic sections; light detection and ranging (lidar) datasets; the Soil Survey Geographic Database; and lithologic well logs from the National Water Information System, New York State Department of Environmental Conservation, New York State Department of Transportation, and Empire State Organized Geologic Information System databases. Digital maps of the surficial geology; thickness of the surficial sand and gravel aquifers; and tops of the confining lacustrine silt and clay units, confined sand and gravel aquifers, and bedrock surfaces were created by using ArcGIS (a geographic information system). All surfaces and thicknesses were generated by using one of the following ArcGIS interpolation tools: Topo to Raster, Natural Neighbors, Kriging, or Empirical Bayesian Kriging. The datasets developed in this study provide a greater understanding of the underlying hydrogeologic framework in glacial valley-fill aquifers and can be applied in the evaluation of groundwater-supply development and protection.

New York↗

USGS2021

Protocol for route restoration in California’s desert renewable energy conservation plan area

In the deserts of the Southwestern United States, increased off-highway vehicle use can lead to widespread vehicular damage to desert ecosystems. As the popularity and intensity of vehicle use on public lands continues, the Bureau of Land Management (BLM) is challenged to manage the routes used by recreationists while minimizing activity beyond designated routes and mitigating environmental impacts. Ecosystem function and habitat quality can be degraded by vehicle activities, especially when the activities are occurring outside authorized routes or authorized open areas. Restoration mitigates damage to soils and vegetation; however, methods vary across the desert, results appear to be inconsistent, and standardized monitoring plans do not exist. The Desert Renewable Energy Conservation Plan Land Use Plan Amendment to the California Desert Conservation Area Land Use Plan identified the need for, and directed implementation of, standardized monitoring of restoration, which includes minimizing surface disturbance to agency prescribed levels in areas of critical environmental concern and on California Desert National Conservation Lands. To assist the BLM in implementing the Desert Renewable Energy Conservation Plan Land Use Plan Amendment, we define ecological restoration as the process of halting or minimizing future degradation while simultaneously assisting the recovery of ecosystem function and community composition in relation to intact reference sites. The monitoring strategies provided in this protocol are used to restore degraded ecosystems after use of non-routes has ceased (non-designated routes or vehicle-caused linear disturbances) by applying techniques to improve edaphic properties, hydrologic function, and biotic community composition. This protocol also provides criteria that can be used to distinguish the status of non-routes and land parcels as “restored” or “disturbed.” This protocol was developed by the U.S. Geological Survey, in collaboration with BLM restoration practitioners, to identify standard restoration methods and establish criteria to determine when restoration is achieved. This protocol also develops new methods to increase restoration rates and successes on public lands in the southern California deserts. BLM’s long-term implementation plan for the evaluation of road restoration described in this report is to transition toward managing the work, including developing the workforce and long-term storage and management of the data during the next several years. This report is intended to be regularly updated as the program develops.

California↗

USGS2018

Crowding affects health, growth, and behavior in headstart pens for Agassiz's desert tortoise

Worldwide, scientists have headstarted threatened and endangered reptiles to augment depleted populations. Not all efforts have been successful. For the threatened Agassiz's desert tortoise ( Gopherus agassizii ), one challenge to recovery is poor recruitment of juveniles into adult populations, and this is being addressed through headstart programs. We evaluated 8 cohorts of juvenile desert tortoises from 1 to 8 yrs old in a headstart program at Edwards Air Force Base, California, for health, behavior, and growth. We also examined capacities of the headstart pens. Of 148 juveniles evaluated for health, 99.3% were below a prime condition index; 14.9% were lethargic and unresponsive; 59.5% had protruding spinal columns and associated concave scutes; 29.1% had evidence of ant bites; and 14.2% had moderate to severe injuries to limbs or shell. Lifetime growth rates for juveniles 1–8 yrs of age were approximately two times less than growth rates reported for wild populations. Tortoises in older cohorts had higher growth rates, and models indicated that high density in pens and burrow sharing negatively affected growth rates. Densities of tortoises in pens (205–2042/ha) were 350–3500 times higher than the average density recorded in the wild (< 1/ha) for tortoises of similar sizes. The predominant forage species available to juveniles were alien annual grasses, which are nutritionally inadequate for growth. We conclude that the headstart pens were of inadequate size, likely contained too few shelters, and lacked the necessary biomass of preferred forbs to sustain the existing population. Additional factors to consider for future reptilian headstart pens include vegetative cover, food sources, soil seed banks, and soil composition.

California↗

USGS2014

Temperature sensitivity of organic-matter decay in tidal marshes

Approximately half of marine carbon sequestration takes place in coastal wetlands, including tidal marshes, where organic matter contributes to soil elevation and ecosystem persistence in the face of sea-level rise. The long-term viability of marshes and their carbon pools depends, in part, on how the balance between productivity and decay responds to climate change. Here, we report the sensitivity of labile soil organic-matter decay in tidal marshes to seasonal and latitudinal variations in temperature measured over a 3-year period. We find a moderate increase in decay rate at warmer temperatures (3-6% per °C, Q 10 = 1.3-1.5). Despite the profound differences between microbial metabolism in wetlands and uplands, our results indicate a strong conservation of temperature sensitivity. Moreover, simple comparisons with organic-matter production suggest that elevated atmospheric CO 2 and warmer temperatures will accelerate carbon accumulation in marsh soils, and potentially enhance their ability to survive sea-level rise.

Biogeosciences↗

USGS2018

Monitoring the water-quality response of agricultural conservation practices in the Bucks Branch watershed, Sussex County, Delaware, 2014–16

The purpose of this study was to evaluate the effects of irrigation and cover crops as conservation practices on water quality in groundwater and streams. Bucks Branch, a stream in the Nanticoke River watershed in southwestern Delaware, was identified as having one of the highest concentrations of nitrate in all surface-water sites sampled by the Delaware Department of Natural Resources and Environmental Control (DNREC). The study site is on two adjacent fields bordering Bucks Branch, one that has used irrigation since 2000 and one with dryland farming; both under conservation tillage and long-term rotation of corn, soybean, and small grain crops. A streamgage was installed near the study site fields to measure streamflow and water quality. The study area is typical of farming practices and environmental conditions throughout much of the intensively farmed agricultural land of the Coastal Plain of Delaware and surrounding parts of Maryland. Monitoring was conducted from January 2014 through June 2016. Corn was grown on both fields during the two growing seasons of the study period, and cover crops were planted before or shortly after harvest on both fields. During the second year of data collection, the effects of radish and rye grass cover crops on nutrient transport were studied. The combined results from data collected for this study show that water and nitrate moved below the root zone year round when soil moisture was high, especially after significant rainfall and frequently after irrigation. Soil water sampled 2 to 3 weeks after nutrients were applied had nitrate concentrations greater than 50 milligrams per liter as nitrogen (mg/L as N) and may be a significant source of nitrate to groundwater. Whereas recharge containing elevated nitrate concentrations also occurred under the dryland field, it was less frequent and of lower concentration than recharge under the irrigated field. Nitrate was present in all groundwater samples from these sites. Groundwater estimated to have recharged within 10 years or less had higher median concentrations of nitrate than in older water samples. The oldest groundwater encountered was over 30 years old, and had traveled along the longest, deep flowpaths from upland fields to the stream. The median nitrate concentration was 18 mg/L as N in younger water (less than 10 years old) beneath the irrigated field, compared to about 10 mg/L as N in younger water beneath the dryland field. Samples from the shallow upland wells in both study fields showed little, if any, evidence of denitrification. Several samples from deeper wells and from wells near forested riparian zone wetlands that border both fields did show partial denitrification. A mixing model estimated that between 12 and 22 percent of the nitrate discharging to the stream was lost through uptake and denitrification upstream of the streamgage on Bucks Branch. Continuous data collected at this site and evidence of denitrification in the surface-water samples showed a greater potential for loss of nitrate during the warmer months than the colder months. This pattern was similar to that seen below the streamgage at the most downstream site in the watershed. A mixed cover crop of radishes and rye was planted prior to removal (radishes) and just after harvest (rye) of the corn crop on the irrigated field. Rye grass was planted shortly after crop harvest on the dryland field. Cover crop biomass samples collected while radishes were growing and after they were killed by freezing temperatures indicates that the early planted radish crop effectively scavenged available nitrogen from the soil. Whereas radish biomass initially held more nitrogen than rye, at 55 to 8 pounds per acre, respectively, leaching of inorganic nitrate following radish die-off was minimal. Soil-water nitrate concentrations during the cover-crop growing period were lower than during the growing season prior to planting of the cover crop. There also was an increase in soil fertility and dissolved organic nitrate in samples of soil water that was likely related to increased soil microbial metabolism. Results indicate that cover crops stored plant nutrients over the winter and did not increase shallow groundwater concentrations of nitrate. Although conservation practices such as cover crops and nutrient management have been applied to these fields, there was still significant leaching of nitrate to groundwater, especially under the irrigated field. This will likely continue to be a challenge in this area and other parts of the Coastal Plain where soil moisture capacity is relatively low and managing irrigation around rainfall is difficult. Cover crops, when planted in standing corn, are one practice that can effectively pull nitrate from below the root zone to the top layer of soil, thus limiting the amount of potential nitrate leaching to groundwater. Irrigation management that would lower average soil moisture conditions during the growing season also could potentially limit nitrogen transport.

Delaware↗

USGS2014

Pedological and geological relationships with soil lichen and moss distribution in the eastern Mojave Desert, CA, USA

Biological soil crusts (biocrusts) are ubiquitous in drylands globally. Lichens and mosses are essential biocrust components and provide a variety of ecosystem services, making their conservation and management of interest. Accordingly, understanding what factors are correlated with their distribution is important to land managers. We hypothesized that cover would be related to geologic and pedologic factors. We sampled 32 sites throughout the eastern Mojave Desert, stratifying by parent material and the age of the geomorphic surfaces. The cover of lichens and mosses on ‘available ground’ (L + M av ; available ground excludes ground covered by rocks or plant stems) was higher on limestone and quartzite-derived soils than granite-derived soils. Cover was also higher on moderately younger-aged geomorphic surfaces (Qya2, Qya3, Qya4) and cutbanks than on very young (Qya1), older-aged surfaces (Qia1, Qia2), or soils associated with coppice mounds or animal burrowing under Larrea tridentata. When all sites and parent materials were combined, soil texture was the most important factor predicting the occurrence of L + M av , with cover positively associated with higher silt, very fine sand, and fine sand fractions and negatively associated with the very coarse sand fraction. When parent materials were examined separately, nutrients such as available potassium, iron, and calcium became the most important predictors of L + M av cover.

California↗

USGS2016

Sediment data collected in 2014 from Barnegat Bay, New Jersey

In response to the 2010 Governor’s Action Plan to clean up the Barnegat Bay–Little Egg Harbor (BBLEH) estuary in New Jersey, the U.S. Geological Survey (USGS) partnered with the New Jersey Department of Environmental Protection in 2011 to begin a multidisciplinary research project to understand the physical controls on water quality in the bay. Between 2011 and 2013, USGS scientists mapped the geological and morphological characteristics of the seafloor of the BBLEH estuary using a suite of geophysical tools. However, this mapping effort included only surficial characterization of bay sediments; to verify the sub-surface geophysical data, sediment cores were required. This report serves as an archive of sedimentologic data from 18 vibracores collected from Barnegat Bay between May and August of 2014 by the U.S. Department of Agriculture Natural Resources Conservation Service (NRCS) on behalf of the USGS. The vibracores were collected in conjunction with an ongoing NRCS subaqueous soil survey for the BBLEH estuary. The data presented in this report, including descriptive core logs, core photographs, processed grain-size data, and Geographic Information System (GIS) data files with accompanying formal Federal Geographic Data Committee metadata, can be viewed or downloaded from the Data Products and Downloads page.

New Jersey↗

USGS2009

The lost micro-deserts of the Patuxent River using landscape history, insect and plant specimens, and field work to detect and define a unique community

Historical and recent records of both plants and insects are synthesized for uplands along the eastern edge of Maryland?s Patuxent River from the edge of the Piedmont south to Jug Bay. This strip is characterized by deep sandy soils found in the Evesboro and Galestown sandy loams soil series. Within this narrow strip there exists a unique flora and fauna adapted to open dry sandy soils and occurring in small remnant patches associated with old sand mining operations and scattered protected areas. We illustrate the uniqueness of these sites using four groups, vascular plants, tenebrionid beetles (Coleoptera: Tenebrionidae), tiger beetles (Coleoptera: Cicindelidae), and bees (Hymenoptera: Apoidea: Anthophila). Within each of these groups, rare species were detected whose populations were locally restricted to this soil type and whose nearest known populations were often hundreds of kilometers away. In addition to documenting the direct conservation importance of these small sandy openings along the Patuxent, we contrast the lack of any indication from vertebrate inventories that this region is unique. The combination of plant and insect inventories appears to be a better means of clarifying a site?s importance than does any survey of a single taxonomic group.

Proceedings of the Entomological Society of Washin↗

USGS2012

Quantification of water-level variability effect on plant species populations using paleoecological and hydrological time series data

Soil cores provide valuable data on historical changes in vegetation and hydrologic conditions. Empirical models were developed to quantify the effect of meteorological and hydrologic forcing on plant species distributions over a 110-year period in Water Conservation Area 1 (WCA1) in the Florida Everglades, also known as the Arthur R. Marshall Loxahatchee National Wildlife Refuge. Empirical models that predict plant species distributions at sites within WCA1 were developed by linking temporally sparse seed bank data from soil cores with continuous multi-decadal daily meteorological and hydrologic time series data. The meteorological data included rainfall and maximum daily temperatures that spanned the entire study period of 110 years. The hydrologic data included stage data from two gages in WCA1 established in 1954. These stage data were hindcasted to be concurrent with the meteorological data by using correlation models that fit measured stages as a function of the meteorological parameters. The historical plant species data came from seven peat cores from WCA1. Different depths from each core were carbon-dated and assayed for relative percentages of 83 plant species using pollen counts. The oldest dates were more than 1,000 years old; however, only core data that overlapped the study period were used, for a total of 67 assays among the seven cores. Twenty-three of the species had ratios of at least 5 percent for one or more of the 67 assays, hereafter referred to as the "top23". Using the assays as input vectors, the top23 were grouped using the k-means clustering into four plant classes that represented the extent to which the various species have historically appeared together. This reduced the modeling problem to one of predicting the relative ratios of the four plant classes from the hindcasted stage time-series data. A separate empirical model was developed for each class using a multi-layer perceptron artificial neural network, which provides multivariate, nonlinear curve fitting. The models predicted the relative ratios of the classes, and the sums of the predictions are near 1. The coefficient of determination (R2) of the models varied from 0.87 to 0.96, indicating that the relative ratios of the plant classes are predictable, and therefore controllable, from stage forcing. Similar soil cores are available for the Coastal Plain of North Carolina and are planned for the Congaree National Park in South Carolina.

Florida↗

USGS2023

Machine-learning model to delineate sub-surface agricultural drainage from satellite imagery

Knowing subsurface drainage (tile-drain) extent is integral to understanding how landscapes respond to precipitation events and subsequent days of drying, as well as how soil characteristics and land management influence stream response. Consequently, a time series of tile-drain extent would inform one aspect of land management that complicates our ability to explain streamflow and water-quality as a function of climate variability or conservation management. We trained a UNet machine-learning model, a convolutional neural network designed to highlight objects of interest within an image, to delineate tile-drain networks in panchromatic satellite imagery without additional data on soils, topography, or historical tile-drain extent. This was done by training the model to match the accuracy of human experts manually tracing the surface representation of tile drains in satellite imagery. Our approach began with a library of images that were used to train and quantify the accuracy of the model, with model performance tested on imagery from two areas that were not used to train the model. Satellite imagery included acquisition dates from 2008 to 2020. Training imagery was from agricultural areas within the US Great Lakes basin. Validation imagery was from the upper Maumee River, tributary to western Lake Erie, and an Indiana, Ohio-River headwater tributary. Our analysis of the satellite imagery paired with meteorological and soil data found that during spring, a combination of relatively high solar radiation, intermediate soil-water content and bare fields enabled the best model performance. Each area of interest was heavily tile-drained, where better understanding the movement of water, nutrients, and sediment from fields to downstream water bodies is key to managing harmful algal blooms and hypoxia. The trained UNet model successfully identified tile drains visible in the validation imagery with an accuracy of 93%–96% and balanced accuracy of 52%–54%, similar to performance for training data (95% and 63%, respectively). Model performance will benefit from ongoing contributions to the training library.

Indiana, Michigan, Ohio, Wisconsin↗

USGS1999

Ground-water quality and susceptibility of ground water to effects from domestic wastewater disposal in eastern Bernalillo County, central New Mexico, 1990-91

Eastern Bernalillo County is a historically rural, mountainous area east of Albuquerque, New Mexico. Historically, the primary economic activity consisted of subsistence farming and ranching and support of these activities from small communities. During the last 40 to 50 years, however, the area increasingly has become the site of residential developments. Homes in these developments typically are on 1- to 2-acre lots and are serviced by individual wells and septic systems. Between 1970 and 1990, the population of the area increased from about 4,000 to more than 12,000, and housing units increased from about 1,500 to more than 5,000. Results of analysis of water samples collected from 121 wells throughout eastern Bernalillo County in 1990 indicated that (1) total-nitrate concentrations in 10 samples exceeded the U.S. Environmental Protection Agency national primary drinking-water regulation maximum contaminant level of 10 milligrams per liter as nitrogen; (2) total-nitrate concentrations may be related to the length of time an area has been undergoing development; and (3) large dissolved-chloride concentrations may result from geologic origins, such as interbedded salt deposits or upward movement of saline ground water along faults and fractures, as well as from domestic wastewater disposal. Ground water throughout eastern Bernalillo County was assessed to be highly susceptible to contamination by overlying domestic wastewater disposal because (1) soils in more than 95 percent of eastern Bernalillo County were determined by the U.S. Department of Agriculture Natural Resources Conservation Service to have severe limitations for use as septic-system absorption fields and (2) a fractured carbonate geologic terrane, which typically has large secondary permeability and limited sorption capacity, is at the surface or underlying unconsolidated material in 73 percent of the area. Ground-water-level rises following an episodal precipitation event during July 22-27, 1991, were large and rapid, particularly in the fractured carbonate terrane. This response indicates a significant hydraulic connection between the land surface and the water table.

Water-Resources Investigations Report↗

USGS2020

Detecting cover crop end-of-season using VENµS and sentinel-2 satellite imagery

Cover crops are planted during the off-season to protect the soil and improve watershed management. The ability to map cover crop termination dates over agricultural landscapes is essential for quantifying conservation practice implementation, and enabling estimation of biomass accumulation during the active cover period. Remote sensing detection of end-of-season (termination) for cover crops has been limited by the lack of high spatial and temporal resolution observations and methods. In this paper, a new within-season termination (WIST) algorithm was developed to map cover crop termination dates using the Vegetation and Environment monitoring New Micro Satellite (VENµS) imagery (5 m, 2 days revisit). The WIST algorithm first detects the downward trend (senescent period) in the Normalized Difference Vegetation Index (NDVI) time-series and then refines the estimate to the two dates with the most rapid rate of decrease in NDVI during the senescent period. The WIST algorithm was assessed using farm operation records for experimental fields at the Beltsville Agricultural Research Center (BARC). The crop termination dates extracted from VENµS and Sentinel-2 time-series in 2019 and 2020 were compared to the recorded termination operation dates. The results show that the termination dates detected from the VENµS time-series (aggregated to 10 m) agree with the recorded harvest dates with a mean absolute difference of 2 days and uncertainty of 4 days. The operational Sentinel-2 time-series (10 m, 4–5 days revisit) also detected termination dates at BARC but had 7% missing and 10% false detections due to less frequent temporal observations. Near-real-time simulation using the VENµS time-series shows that the average lag times of termination detection are about 4 days for VENµS and 8 days for Sentinel-2, not including satellite data latency. The study demonstrates the potential for operational mapping of cover crop termination using high temporal and spatial resolution remote sensing data.

Remote Sensing↗

USGS2011

Assessment of hyporheic zone, flood-plain, soil-gas, soil, and surface-water contamination at the Old Incinerator Area, Fort Gordon, Georgia, 2009-2010

The U.S. Geological Survey, in cooperation with the U.S. Department of the Army Environmental and Natural Resources Management Office of the U.S. Army Signal Center and Fort Gordon, Georgia, assessed the hyporheic zone, flood plain, soil gas, soil, and surface-water for contaminants at the Old Incinerator Area at Fort Gordon, from October 2009 to September 2010. The assessment included the detection of organic contaminants in the hyporheic zone, flood plain, soil gas, and surface water. In addition, the organic contaminant assessment included the analysis of explosives and chemical agents in selected areas. Inorganic contaminants were assessed in soil and surface-water samples. The assessment was conducted to provide environmental contamination data to the U.S. Army at Fort Gordon pursuant to requirements of the Resource Conservation and Recovery Act Part B Hazardous Waste Permit process. Total petroleum hydrocarbons were detected above the method detection level in all 13 samplers deployed in the hyporheic zone and flood plain of an unnamed tributary to Spirit Creek. The combined concentrations of benzene, toluene, ethylbenzene, and total xylene were detected at 3 of the 13 samplers. Other organic compounds detected in one sampler included octane and trichloroethylene. In the passive soil-gas survey, 28 of the 60 samplers detected total petroleum hydrocarbons above the method detection level. Additionally, 11 of the 60 samplers detected the combined masses of benzene, toluene, ethylbenzene, and total xylene above the method detection level. Other compounds detected above the method detection level in the passive soil-gas survey included octane, trimethylbenzene, perchlorethylene, and chloroform. Subsequent to the passive soil-gas survey, six areas determined to have relatively high contaminant mass were selected, and soil-gas samplers were deployed, collected, and analyzed for explosives and chemical agents. No explosives or chemical agents were detected above their method detection levels, but those that were detected were above the nondetection level. The same six locations that were sampled for explosives and chemical agents were selected for the collection of soil samples. No metals that exceeded the Regional Screening Levels for Industrial Soils as classified by the U.S. Environmental Protection Agency were detected at any of the six Old Incinerator Area locations. The soil samples also were compared to values from the ambient, uncontaminated (background) levels for soils in South Carolina. Because South Carolina is adjacent to Georgia and the soils in the coastal plain are similar, these comparisons are valid. No similar values are available for Georgia to use for comparison purposes. The only metal detected above the ambient background levels for South Carolina was barium. A surface-water sample collected from a tributary west and north of the Old Incinerator Area was analyzed for volatile organic compounds, semivolatile organic compounds, and inorganic compounds (metals). The only volatile organic and (or) semivolatile organic compound that was detected above the laboratory reporting level was toluene. The compounds 4-isopropyl-1-methylbenzene and isophorone were detected above the nondetection level but below the laboratory reporting level and were estimated. These compounds were detected at levels below the maximum contaminant levels set by the U.S. Environmental Protection Agency National Primary Drinking Water Standard. Iron was the only inorganic compound detected in the surface-water sample that exceeded the maximum contaminant level set by the U.S. Environmental Protection Agency National Secondary Drinking Water Standard. No other inorganic compounds exceeded the maximum contaminant levels for the U.S. Environmental Protection Agency National Primary Drinking Water Standard, National Secondary Drinking Water Standard, or the Georgia In-Stream Water Quality Standard.

Georgia↗

USGS2024

Unburned habitat essential for amphibian breeding persistence following wildfire

Wildfire regimes are changing rapidly with widespread increase in the intensity, frequency, and duration of fire activity, especially in the western United States. Limited studies explore the impacts of wildfires on aquatic taxa and few focus on lentic habitats that are essential for amphibians, many of which are of conservation concern. We capitalized on existing pre-fire surveys for anuran species and resurveyed a random subset of wetlands across a gradient of soil burn severity to investigate the short-term effects of wildfire on a relict population of wood frogs in the southern Rocky Mountains. We also investigated whether maps created to support rapid post-fire emergency response activities (i.e., United States Forest Service Burned Area Emergency Response program) accurately characterize soil burn severity around small habitat features (i.e., ponds) that serve as important amphibian breeding and rearing habitat. Soil burn severity reflects fire impacts on soil and surface organic layers, including vegetation loss and changes in soil structure and function. We found that wood frog ( Lithobates sylvaticus ) breeding persistence following fires was negatively influenced by the percentage of their terrestrial habitat (100 m buffer surrounding breeding ponds) that was burned. Wood frog colonization probability of previously unoccupied ponds was low (∼ 0.10) and unaffected by soil burn severity. Importantly, we found that remotely sensed data typically produced to predict flooding and erosion at broad (catchment) scales is a poor representation of the amount and variation in soil burn severity surrounding small habitat features, suggesting that additional field sampling is necessary to understand wildfire responses for species that rely on these small habitat features. Understanding short-term geographic- and species-specific variation in response to wildfires provides the basis to explore time to recovery (e.g., when wood frogs return to burned breeding sites) or to determine if declines in breeding distributions intensify over time.

Wyoming↗

USGS2013

Hydrologic controls on the transport and cycling of carbon and nitrogen in a boreal catchment underlain by continuous permafrost

Boreal ecosystems represent a large carbon (C) reservoir and a substantial source of greenhouse gases. Hydrologic conditions dictate whether C leached from boreal soils is processed in catchments or flushed to less productive environments via the stream. This study quantified hydrologic and biogeochemical C loss from a boreal catchment underlain by frozen silt, where flowpaths may deepen as the active layer thaws over the summer. We hypothesized a decrease in the magnitude of C mineralization over the summer associated with changing flowpaths and decreasing hydrologic connectivity, organic matter lability, and nitrogen (N) availability. Conservative tracers were used to partition C and N loss between catchment export and biogeochemical processing. Coupling tracers with tributary and porewater chemistry indicated C and N cycling in soil flowpaths, with an exponential decrease over the summer. Nitrate was primarily reduced in hillslope flowpaths and the lack of N reaching the stream appeared to limit C mineralization. Stream export accounted for the greatest loss of C, removing 247 and 113 mol hr −1 in the early and late summer, respectively. Reactivity was related to hydrologic connectivity between the soils and stream, which was greatest early in the summer and following a large flood. While a warming climate may increase storage potential in thawed soils, the early‐season flush of labile material and late‐season runoff through mineral flowpaths may maintain high C export rates. Therefore, we highlight physical export as a dominant cause of aqueous C loss from silty catchments as the Arctic continues to thaw.

Journal of Geophysical Research G: Biogeosciences↗

USGS2011

Sulfate threshold target to control methylmercury levels in wetland ecosystems

Sulfate contamination has a significant environmental implication through the stimulation of toxic hydrogen sulfide and methylmercury (MeHg) production. High levels of MeHg are a serious problem in many wetland ecosystems worldwide. In the Florida Everglades, it has been demonstrated that increasing MeHg occurrence is due to a sulfate contamination problem. A promising strategy of lowering the MeHg occurrence is to reduce the amount of sulfate entering the ecosystem. High surface water sulfate concentrations in the Everglades are mainly due to discharges from the Everglades Agricultural Area (EAA) canals. Water and total sulfur mass balances indicated that total sulfur released by soil oxidation, Lake Okeechobee and agricultural application were the major sources contributing 49,169, 35,217 and 11,775mtonsyear-1, respectively. Total sulfur loads from groundwater, levees, and atmospheric deposition contributed to a lesser extent: 4055; 5858 and 4229mtonsyear-1, respectively. Total sulfur leaving the EAA into Water Conservation Areas (WCAs) through canal discharge was estimated at 116,360mtonsyear-1, and total sulfur removed by sugarcane harvest accounted for 23,182mtonsyear-1. Furthermore, a rise in the mineral content and pH of the EAA soil over time, suggested that the current rates of sulfur application would increase as the buffer capacity of the soil increases. Therefore, a site specific numeric criterion for sulfate of 1mgL-1 was recommended for the protection of the Everglades; above this level, mercury methylation is enhanced. In parallel, sulfide concentrations in the EAA exceeded the 2??gL-1 criterion for surface water already established by the U.S. Environmental Protection Agency (EPA). ?? 2011 Elsevier B.V.

Science of the Total Environment↗

USGS2023

Techniques for restoring damaged Mojave and western Sonoran ecosystems, including those for threatened desert tortoises and Joshua trees

Ecological restoration has potential for contributing to conservation activities for threatened Mojave desert tortoises ( Gopherus agassizii ) and Joshua trees ( Yucca brevifolia , Y. jaegeriana ) and their broader ecosystems in the Mojave and western Sonoran deserts. To be effective, restoration actions deployed strategically need to halt and reverse habitat degradation, replenish or enhance resources used by both species (e.g., large shrubs for protection of tortoises and nurse plants facilitating recruitment of Joshua tree seedlings), and ideally foster resilience during likely future environmental changes. We synthesized restoration techniques and their effectiveness in the Mojave and western Sonoran deserts, provide estimated costs of candidate techniques, and anticipate future research needs for effective restoration in changing climates and environments. Over 50 published studies in the Mojave and western Sonoran deserts demonstrate that restoration can improve soil features (e.g., biocrusts), increase cover of native perennial and annual plants, enhance native seed retention and seed banks, and reduce risk of fires to conserve mature shrubland habitat. We placed restoration techniques into three categories: restoration of site environments, revegetation, and management actions to limit further disturbance and encourage recovery. Within these categories, 11 major restoration techniques (and their variations) were evaluated by at least one published study and range from geomorphic (e.g., reestablishing natural topographic patterns) and abiotic structural treatments (e.g., vertical mulching) to active revegetation (e.g., outplanting, seeding). For example, 16 outplanting studies assessed performance of 46 species to begin identifying top-performing species, associated treatments (e.g., protection from herbivory) required to aid outplant survival, and potential for outplants to trigger formation of self-sustaining populations. Creosote bush (Larrea tridentata), a shrub that tortoises use for cover and that serves as a nurse plant for Joshua tree recruitment, achieved at least 50% survival in five of eight studies. Estimated costs for restoring desert habitats varied primarily with the severity of the disturbance, site factors including the diversity of vegetation that was lost, logistical factors such as accessibility of sites (influencing transportation costs), and the cost-effectiveness of the restoration techniques chosen. The review highlights six major research and adaptive management needs for advancing desert habitat restoration. These needs include: 1) continued development of innovative techniques and bet-hedging approaches to provide managers with “tool boxes” of candidate treatments to deploy in dynamic environmental and management conditions, 2) identifying how to optimize spatial deployment of limited restoration resources, 3) developing practical techniques for reducing non-native annual grasses across spatial scales, 4) improving linkages between habitat enhancements and short- and long-term indicators of tortoise usage and responses and Joshua tree population sustainability, 5) mitigating multiple, interacting stressors with cumulative impacts, and 6) integrating biotic (e.g., seeding) and abiotic (e.g., fencing, shade structures) treatments to complement each other at site and landscape scales in dynamic climates and environments. It is possible that bet-hedging approaches employing multiple treatment types (or phased treatments across years) and greater incorporation of abiotic treatments, which are less sensitive to timing of precipitation compared with biotic treatments, will become increasingly important under future climates projected to be drier and more variable. Existing research suggests that restoration can be deployed effectively even under adverse climatic conditions, but success requires identifying suitable techniques tailored to dynamic environments.

Arizona, California, Nevada, Sonora↗