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At least 217 records · Page 12Linked to original sources

USGS2010

Comparison of Penman-Monteith, Shuttleworth-Wallace, and modified Priestley-Taylor evapotranspiration models for wildland vegetation in semiarid rangeland

Eddy correlation measurements of sensible and latent heat flux are used with measurements of net radiation, soil heat flux, and other micrometeorological variables to develop the Penman-Monteith, Shuttleworth-Wallace, and modified Priestley-Taylor evapotranspiration models for use in a sparsely vegetated, semiarid rangeland. The Penman-Monteith model, a one-component model designed for use with dense crops, is not sufficiently accurate ( r 2 = 0.56 for hourly data and r 2 = 0.60 for daily data). The Shuttleworth-Wallace model, a two-component logical extension of the Penman-Monteith model for use with sparse crops, performs significantly better ( r 2 = 0.78 for hourly data and r 2 = 0.85 for daily data). The modified Priestley-Taylor model, a one-component simplified form of the Penman potential evapotranspiration model, surprisingly performs as well as the Shuttle worth-Wallace model. The rigorous Shuttleworth-Wallace model predicts that about one quarter of the vapor flux to the atmosphere is from bare-soil evaporation. Further, during daylight hours, the small leaves are sinks for sensible heat produced at the hot soil surface.

Water Resources Research↗

USGS1978

Dating Quaternary faults in the southwestern United States by using buried calcic paleosols

Calcareous soils are widespread on upper Pliocene to upper Pleistocene unconsolidated surflcial deposits in semiarid portions of the southwestern United States. Where these soils are related to faults, the soils may provide a means for quantitatively estimating timing and amounts of Quaternary faulting. Soil age estimates are based on the amount of pedogenic CaCO 3 (g/cm 2 -soil column) that has accumulated from soil processes, whereas rates of calcic-soil formation were calibrated by the K-Ar dating method, tephrochronology, vertebrate paleontology, and regional soil studies. The County Dump fault, west of Albuquerque, N. Mex. cuts a 500 000-yearold datum, the Llano de Albuquerque. The downdropped block of this fault contains a sequence of faulted younger deposits and intercalated calcic paleosols. Soil ages, and hence fault ages, can be calculated by measuring the total pedogenic calcium carbonate content in a section of buried paleosols and by using an independently established maximum soil formation rate of 0.35 g CaCO 3 • cm -2 • 10 -3 yr -1 for the Albuquerque area. This particular fault segment has had four discrete episodes of movement in the past 500 000 yr, the most recent of which occurred about 20000 yr B.P. Recurrence intervals on the segment are 90 000-190 000 yr, but the composite recurrence interval for all fault movements in this area may be less by several orders of magnitude. This technique of quantifying soil properties and calculating ages of relict soils can be used to estimate ages of Quaternary deposits and associated surfaces, to correlate such features over broad regions, and to analyze regional trends in calcic-soil formation.

New Mexico↗

USGS2026

Core microbiomes as a potential fingerprinting method of Western USA dust sources

Introduction: Changing frequency and intensity of dust emissions impacts ecosystems and human health. Dust carries microbes, nutrients, heavy metals, and other materials that may change environmental biogeochemistry at deposition sites. Identifying dust sources provides key information on where and when mitigation strategies should be employed. However, commonly used geochemical or isotopic tracers are often not capable of distinguishing between geographic regions. Methods: We explored whether soil bacterial communities may provide distinct fingerprints of dust sources in the western United States. We identified bacterial core communities of dust from ten locations monitored by the National Wind Erosion Research Network (NWERN) with varied land use (cropland, rangeland, and playa), and compared communities to location, soil, and regional characteristics. Samples were collected monthly from Modified Wilson and Cooke (MWAC) samplers, composited by season (spring, summer, and fall), and analyzed using 16S rRNA sequencing. Results: We found distinct bacterial core communities that reflected dust source characteristics. In order of importance, precipitation levels ( p = 0.0001), location ( p = 0.0001), soil texture ( p = 0.0001), seasonality ( p = 0.0001), and elevation (p = 0.0002) were correlated with bacterial community composition. Discussion: Distinct bacterial core communities were associated with site characteristics such as biocrusts, playas, and military base proximity. Our results suggest that the use of core microbiomes may offer a fingerprinting method to identify dust source regions.

Colorado, Nevada, New Mexico, North Dakota, Oklaho↗

USGS2002

Environmental impacts of petroleum production: Fate of inorganic and organic chemicals in produced water from the Osage-Skiatook Petroleum Environmental Research sites, Osage County, Oklahoma

About 15 scientists from the U. S. Geological Survey, other Federal agencies and academia are involved in a multidisciplinary investigation to study the transport, fate, and natural attenuation of inorganic salts, trace metals, radionuclides and organic compounds present in produced water, and their impacts on soil, surface and ground water and the local ecosystem at the Osage-Skiatook Petroleum Environmental Research (OSPER) A and B sites, located in Osage County, OK. The Branstetter lease, OSPER B site, is typical of many aging petroleum fields in Osage County, which ranks among the top oil and gas producing counties in Oklahoma with close to 40,000 wells. Current production in Osage County is mainly from stripper wells (averaging ~2.8 bbls/d oil and >30 bbls/d brine) that are shallow, mostly 300-700 m in depth, and produce from several sandstones of Pennsylvanian age. About one hectare of land at the OSPER B site is affected by salt scarring, soil salinization and brine and petroleum contamination due to the leakage of produced water and associated hydrocarbons from two brine pits and due to accidental releases from active tank batteries. Eventually, the bulk of inorganic salts and some dissolved organic species in the released brine reach, directly or via the two local streams, the adjacent Skiatook Lake, a 4250-hectare reservoir that provides drinking water to the local communities and is a major recreational fishery. About 40 water samples were obtained from several oil wells at the B site and adjoining areas, the two brine pits, several brine pools and seeps in the impacted area, local streams, Skiatook Lake, and from about 20 boreholes (1-71 m deep), recently drilled and completed with slotted PVC tubing. Water level monitoring and additional sampling is continuing. Results to date show that the produced water is a high-salinity (~150,000 mg/L total dissolved solids) Na-Ca-Cl brine, with relatively high concentrations of Sr, Mg and NH4, but low amounts of SO4 and H2S. With the exception of Fe and Mn, the concentrations of trace metals are low, and the values of dissolved organics are relatively low. As the brine flows from the brine pits through the shallow eolian sand, colluvial and alluvial deposits to the streams and Skiatook Lake, it is diluted by infiltrating water from precipitation. Its chemical composition is modified by sorption, mineral precipitation/dissolution, transpiration, volatilization and oxidation/reduction reactions. Bacteria likely play an important role in many of these reactions.

Oklahoma↗

USGS2003

Environmental impacts of petroleum production--Initial results from the Osage-Skiatook Petroleum Environmental Research Sites, Osage County, Oklahoma

Exploration for and production of petroleum have caused major detrimental impacts to soils, surface and ground waters, and the local ecosystems in the United States. These impacts arise primarily from the improper disposal of large volumes of saline water produced with oil and gas, from accidental hydrocarbon and produced water releases, and from abandoned oil wells that were not correctly sealed. It is important to understand the long-term and short-term effects of produced water and hydrocarbon releases from these sites in order to develop risk-based remediation plans. Remediation is particularly needed in aging and depleted fields where land use is changing from petroleum production to residential, agricultural or recreational uses. About 20 scientists from the USGS and other governmental agencies and academia are involved in a multidisciplinary investigation to study the transport, fate, and natural attenuation of inorganic salts, trace metals, organic compounds and radionuclides present in produced water, and their impacts at the Osage-Skiatook Petroleum Environmental Research (OSPER) "A" and "B" sites, located on the Osage Reservation in Osage County, Oklahoma. Stakeholders in the project include the Osage Nation, which holds the mineral rights, the Bureau of Indian Affairs with trust responsibility, and the Army Corps of Engineers, which owns the surface rights at these sites and manages adjacent Skiatook Lake. The 4250-hectare Skiatook Lake provides drinking water to local Tulsa suburban communities and a rural water district, and offers recreational fishing and boating opportunities to tens of thousands of visitors each year. Approximately 1.5 and 1.0 hectare of land at the OSPER "A" (depleted Lester lease) and "B" (active Branstetter lease) sites, respectively, are affected by salt scarring, tree kills, soil salinization and brine and petroleum contamination due to the leakage of produced water and associated hydrocarbons from brine pits and accidental releases from active and inactive pipes and tank batteries. The leases are typical of many depleted and aging petroleum fields in Osage County, which ranks among the top oil and gas producing counties in Oklahoma with about 39,000 wells. Oil and gas production has occurred in Osage county for over one hundred years, but current production is mainly from stripper wells (averaging ~2.8 bbl/d oil and >30 bbl/d brine) that are shallow, mostly 300-700 m in depth, and produce from several sandstones of Pennsylvanian age. Results to date show that the produced water source is a Na-Ca-Cl brine (~150,000 mg/L total dissolved solids), with relatively high concentrations of Mg, Sr, and NH4, but low SO4 and H2S. With the exception of Fe and Mn, the concentrations of trace metals are low. Results also show that some and, eventually, the bulk, of inorganic salts and some dissolved organic species in the released brine from both sites will reach Skiatook Lake. Results at the "A" site show that the salts have essentially been removed from the sandy soil which formed in a surficial layer of eolian sand, but degraded and weathered oil persists on the surface of old oil and brine pits, close to sites of old tanks, on old channels that carried oil from tanks to the oil pits and other impacted areas. Results also show a plume of high salinity water (5,000-30,600 mg/L TDS) is present at intermediate depths that extend from below the old oil and brine pits to Skiatook Lake. No liquid petroleum was found in the contaminated groundwater, but soluble petroleum byproducts, including organic acid anions and other volatile organic compounds (VOCs) are present. Results to date clearly show that significant amounts of salts from produced-water releases and petroleum hydrocarbons still remain in the soils and rocks of the impacted area after more than 60 years of natural attenuation. At the "B" site significant amounts of produced water from the two active brine pits percolate into the surficial rocks and flow towards the Skiatook Reservoir; but only minor amounts of liquid petroleum leave the brine pits and reach the Skiatook Reservoir. At both sites, results show that the chemical composition of released brines is modified further by sorption, mineral precipitation/dissolution, transpiration, volatilization and bacterially mediated oxidation/reduction reactions.

Oklahoma↗

USGS2016

Migratory bird habitat in relation to tile drainage and poorly drained hydrologic soil groups

The Prairie Pothole Region (PPR) is home to more than 50% of the migratory waterfowl in North America. Although the PPR provides an abundance of temporary and permanent wetlands for nesting and feeding, increases in commodity prices and agricultural drainage practices have led to a trend of wetland drainage. The Northern Shoveler is a migratory dabbling duck species that uses wetland habitats and cultivated croplands in the PPR. Richland County in North Dakota and Roberts County in South Dakota have an abundance of wetlands and croplands and were chosen as the study areas for this research to assess the wetland size and cultivated cropland in relation to hydrologic soil groups for the Northern Shoveler habitat. This study used geographic information system data to analyze Northern Shoveler habitats in association with Natural Resource Conservation Service soil data. Habitats, which are spatially associated with certain hydrologic soil groups, may be at risk of artificial drainage installations because of their proximity to cultivated croplands and soil lacking in natural drainage that may become wet or inundated. Findings indicate that most wetlands that are part of Northern Shoveler habitats were within or adjacent to cultivated croplands. The results also revealed soil hydrologic groups with high runoff potential and low water transmission rates account for most of the soil within the Northern Shoveler‘s wetland and cropland habitats. Habitats near agriculture with high runoff potential are likely to be drained and this has the potential of reducing Northern Shoveler habitat.

Conference Paper↗

USGS2024

Establishing quantitative benchmarks for soil erosion and ecological monitoring, assessment, and management

Soil erosion can have a multitude of negative impacts on agroecosystems and society and there remains an urgent need for tools to support its management. Quantitative benchmarks based on holistic understanding of erosion processes, ecosystem function, and land use objectives can be used with monitoring data and models to inform assessments and make objective and actionable decisions about erosion management. However, managers currently lack a framework for establishing benchmarks. Here, we present a framework and evaluation of different approaches to establishing quantitative benchmarks for soil erosion and ecological monitoring and assessment that can inform land management decisions. We use monitoring data collected across Chihuahuan Desert ecosystems in the United States and an aeolian sediment transport model to illustrate how benchmarks can be established. Approaches include establishing benchmarks from relationships between soil erosion indicators, reference states and land potential, including state-and-transition models, and desired conditions from existing monitoring data. We discuss the benefits and caveats of the different approaches and show how combining different benchmarking approaches can help users ensure that benchmarks appropriately reflect thresholds for soil erosion and achievable management outcomes. We finish by identifying future research needs to support establishment and application of erosion benchmarks across agroecosystems and recognize the opportunity to extend the benchmarking approaches to management of other agroecosystem processes and services.

Ecological Indicators↗

USGS2023

Modeling global indices for estimating non-photosynthetic vegetation cover

Non-photosynthetic vegetation (NPV) includes plant litter, senesced leaves, and crop residues. NPV plays an essential role in terrestrial ecosystem processes, and is an important indicator of drought severity, ecosystem disturbance, agricultural resilience, and wildfire danger. Current moderate spatial resolution multispectral satellite systems (e.g., Landsat and Sentinel-2) have only a single band in the 2000–2500 nm shortwave infrared “SWIR2” range where non-pigment biochemical constituents of NPV, including cellulose and lignin, have important spectral absorption features. Thus, these current systems have suboptimal capabilities for characterizing NPV cover. This research used simulated spectral mixtures accounting for variability among NPV and soils to evaluate globally-appropriate hyperspectral and multispectral indices for estimation of fractional NPV cover. The Continuum Interpolated NPV Depth Index (CINDI), a weighted ratio index measuring lignocellulose absorption near 2100 nm, was found to produce the lowest error in estimating NPV cover. CINDI was less sensitive to variability in soil spectra and green vegetation cover than competing indices. While CINDI was sensitive to the relative water content of soil and NPV, this sensitivity allowed for correcting error in estimated NPV cover as water content increased. CINDI bands were less capable than Dual Absorption NPV Index (DANI) bands for maintaining continuity with the heritage Landsat SWIR2 band, but combining multiple CINDI bands demonstrated adequate continuity. Three SWIR2 bands with band centers at 2038, 2108, and 2211 nm can provide superior capabilities for future moderate resolution multispectral/superspectral systems targeting NPV monitoring, including the next generation Landsat mission (Landsat Next). These bands and the associated CINDI index provide potential for global NPV monitoring using a constellation of future superspectral sensors and imaging spectrometers, with applications including improving soil management, preventing land degradation, evaluating impacts of drought, mapping ecosystem disturbance, and assessing wildfire danger.

Remote Sensing of Environment↗

USGS2012

Coal-tar-based pavement sealcoat and PAHs: implications for the environment, human health, and stormwater management

Coal-tar-based sealcoat products, widely used in the central and eastern U.S. on parking lots, driveways, and even playgrounds, are typically 20−35% coal-tar pitch, a known human carcinogen that contains about 200 polycyclic aromatic hydrocarbon (PAH) compounds. Research continues to identify environmental compartments—including stormwater runoff, lake sediment, soil, house dust, and most recently, air—contaminated by PAHs from coal-tar-based sealcoat and to demonstrate potential risks to biological communities and human health. In many cases, the levels of contamination associated with sealed pavement are striking relative to levels near unsealed pavement: PAH concentrations in air over pavement with freshly applied coal-tar-based sealcoat, for example, were hundreds to thousands of times higher than those in air over unsealed pavement. Even a small amount of sealcoated pavement can be the dominant source of PAHs to sediment in stormwater-retention ponds; proper disposal of such PAH-contaminated sediment can be extremely costly. Several local governments, the District of Columbia, and the State of Washington have banned use of these products, and several national and regional hardware and home-improvement retailers have voluntarily ceased selling them.

Environmental Science & Technology↗

USGS2009

Impact of wildfire on levels of mercury in forested watershed systems: Voyageurs National Park, Minnesota

Atmospheric deposition of mercury to remote lakes in mid-continental and eastern North America has increased approximately threefold since the mid-1800s (Swain and others, 1992; Fitzgerald and others, 1998; Engstrom and others, 2007). As a result, concerns for human and wildlife health related to mercury contamination have become widespread. Despite an apparent recent decline in atmospheric deposition of mercury in many areas of the Upper Midwest (Engstrom and Swain, 1997; Engstrom and others, 2007), lakes in which fish contain levels of mercury deemed unacceptable for human consumption and possibly unacceptable for fish-consuming wildlife are being detected with increasing frequency. In northern Minnesota, Voyageurs National Park (VNP) (fig. 1) protects a series of southern boreal lakes and wetlands situated on bedrock of the Precambrian Canadian Shield. Mercury contamination has become a significant resource issue within VNP as high concentrations of mercury in loons, bald eagle eaglets, grebes, northern pike, and other species of wildlife and fish have been found. The two most mercury-contaminated lakes in Minnesota, measured as methylmercury in northern pike ( Esox lucius ), are in VNP. Recent multidisciplinary U.S. Geological Survey (USGS) research demonstrated that the bulk of the mercury in lake waters, soils, and fish in VNP results from atmospheric deposition (Wiener and others, 2006). The study by Wiener and others (2006) showed that the spatial distribution of mercury in watershed soils, lake waters, and age-1 yellow perch ( Perca flavescens ) within the Park was highly variable. The majority of factors correlated for this earlier study suggested that mercury concentrations in lake waters and age-1 yellow perch reflected the influence of ecosystem processes that affected within-lake microbial production and abundance of methylmercury (Wiener and others, 2006), while the distribution of mercury in watershed soils seemed to be partially dependent on forest disturbance, especially the historic forest fire pattern (Woodruff and Cannon, 2002). Forest fire has an essential role in the forest ecosystems of VNP (Heinselman, 1996). Because resource and land managers need to integrate both natural wildfire and prescribed fire in management plans, the potential influence of fire on an element as sensitive to the environment as mercury becomes a critical part of their decisionmaking. A number of recent studies have shown that while fire does have a significant impact on mercury at the landscape level, the observed effects of fire on aquatic environments are highly variable and unpredictable (Caldwell and others, 2000; Garcia and Carrigan, 2000; Kelly and others, 2006; Nelson and others, 2007). Caldwell and others (2000) described an increase in methylmercury in reservoir sediments resulting from mobilization and transport of charred vegetative matter following a fire in New Mexico. Krabbenhoft and Fink (2000) attributed increases in total mercury concentrations in young-of-the-year fish in the Florida Everglades to release of mercury resulting from peat oxidation following fires. A fivefold increase in whole-body mercury accumulation by rainbow trout ( Oncorhynchus mykiss ) following a fire in Alberta, Canada, apparently resulted from increased nutrient concentrations that enhanced productivity and restructured the food web of a lake within the fire’s burn footprint (Kelly and others, 2006). For this study, we determined the short-term effects of forest fire on mercury concentrations in terrestrial and aquatic environments in VNP by comparing and contrasting mercury concentrations in forest soils, lake waters, and age-1 yellow perch for a burned watershed and an adjacent lake, with similar samples from watersheds and lakes with no fire activity (control watersheds and lakes). The concentration of total mercury in whole, 1-year-old yellow perch serves as a good biological indicator for monitoring trends in methylmercury concentrations in food webs of lakes in North America (Wiener and others, 2007). With a limited gape, age-1 yellow perch that hatched the previous year and resided in a lake for 1 year feed largely on zooplankton and small benthic invertebrates. Thus, age-1 yellow perch provide a baseline for methylmercury concentrations for individual lakes that can be compared across spatial areas. The nine appendixes that accompany this report contain the complete datasets for soils, lake waters, and age-1 yellow perch collected for this study. This report uses data from these three media to provide a framework for evaluating short-term effects of fire on mercury in forested soils and possible effects of the mobilization of mercury from soils on lake water quality and aquatic health.

Minnesota↗

USGS2004

Dust storms and their impact on ocean and human health: dust in Earth's atmosphere

Satellite imagery has greatly influenced our understanding of dust activity on a global scale. A number of different satellites such as NASA's Earth-Probe Total Ozone Mapping Spectrometer (TOMS) and Se-viewing Field-of-view Sensor (SeaWiFS) acquire daily global-scale data used to produce imagery for monitoring dust storm formation and movement. This global-scale imagery has documented the frequent transmission of dust storm-derived soils through Earth's atmosphere and the magnitude of many of these events. While various research projects have been undertaken to understand this normal planetary process, little has been done to address its impact on ocean and human health. This review will address the ability of dust storms to influence marine microbial population densities and transport of soil-associated toxins and pathogenic microorganisms to marine environments. The implications of dust on ocean and human health in this emerging scientific field will be discussed.

EcoHealth↗

USGS2010

Are patterns in nutrient limitation belowground consistent with those aboveground: Results from a 4 million year chronosequence

Accurately predicting the effects of global change on net carbon (C) exchange between terrestrial ecosystems and the atmosphere requires a more complete understanding of how nutrient availability regulates both plant growth and heterotrophic soil respiration. Models of soil development suggest that the nature of nutrient limitation changes over the course of ecosystem development, transitioning from nitrogen (N) limitation in ‘young’ sites to phosphorus (P) limitation in ‘old’ sites. However, previous research has focused primarily on plant responses to added nutrients, and the applicability of nutrient limitation-soil development models to belowground processes has not been thoroughly investigated. Here, we assessed the effects of nutrients on soil C cycling in three different forests that occupy a 4 million year substrate age chronosequence where tree growth is N limited at the youngest site, co-limited by N and P at the intermediate-aged site, and P limited at the oldest site. Our goal was to use short-term laboratory soil C manipulations (using 14 C-labeled substrates) and longer-term intact soil core incubations to compare belowground responses to fertilization with aboveground patterns. When nutrients were applied with labile C (sucrose), patterns of microbial nutrient limitation were similar to plant patterns: microbial activity was limited more by N than by P in the young site, and P was more limiting than N in the old site. However, in the absence of C additions, increased respiration of native soil organic matter only occurred with simultaneous additions of N and P. Taken together, these data suggest that altered nutrient inputs into ecosystems could have dissimilar effects on C cycling above- and belowground, that nutrients may differentially affect of the fate of different soil C pools, and that future changes to the net C balance of terrestrial ecosystems will be partially regulated by soil nutrient status.

Biogeochemistry↗

USGS2026

PFAS in our food: From farms and fields to streams and shores

The concern of per- and polyfluoroalkyl substances (PFAS) contamination has historically focused on drinking water, but communities and researchers are increasingly realizing that drinking water may not be the only important exposure pathway. PFAS move through surface water, sediments and soils into groundwater, wildlife and even our agricultural systems. Consequently, they affect the foods that shape daily life, cultural traditions and community health. Research on dietary PFAS exposure has typically been confined to fish consumption despite the potential for broader impacts given the widespread occurrence of PFAS in the environment.

SETAC Globe↗

USGS1998

Base cation concentrations in subsurface flow from a forested hillslope: The role of flushing frequency

A 20-m-wide trench was excavated to bedrock on a hillslope at the Panola Mountain Research Watershed in the Piedmont region of Georgia to determine the effect of upslope drainage area from the soil and bedrock surfaces on the geochemical evolution of base cation concentrations in subsurface flow. Samples were collected from ten 2-m sections and five natural soil pipes during three winter rainstorms in 1996. Base cation concentrations in hillslope subsurface flow were generally highest early and late in the storm response when flow rates were low, but during peak flow, concentrations varied little. Base cation concentrations in matrix flow from the 10 trench sections were unrelated to the soil surface drainage area and weakly inversely related to the bedrock surface drainage area. Base cation concentrations in pipe flow were lower than those in matrix flow and were also consistent with the inverse relation to bedrock surface drainage area found in matrix flow. The left side of the trench, which has the highest bedrock surface drainage area, had consistently lower mean base cation concentrations than the right side of the trench, which has the lowest bedrock surface drainage area. During moderate size rain events of about 20–40 mm, subsurface flow occurred only on the left side of the trench. The greater volume of water that has flowed through the left side of the trench appears to have resulted in greater leaching of base cations from soils and therefore lower base cation concentrations in subsurface flow than in flow from the right side of the trench. Alternatively, a greater proportion of flow that bypasses the soil matrix may have occurred through the hillslope on the left side of the trench than on the right side. Flushing frequency links spatial hillslope water flux with the evolution of groundwater and soil chemistry.

Georgia↗

USGS2016

Toward more realistic projections of soil carbon dynamics by Earth system models

Soil carbon (C) is a critical component of Earth system models (ESMs), and its diverse representations are a major source of the large spread across models in the terrestrial C sink from the third to fifth assessment reports of the Intergovernmental Panel on Climate Change (IPCC). Improving soil C projections is of a high priority for Earth system modeling in the future IPCC and other assessments. To achieve this goal, we suggest that (1) model structures should reflect real-world processes, (2) parameters should be calibrated to match model outputs with observations, and (3) external forcing variables should accurately prescribe the environmental conditions that soils experience. First, most soil C cycle models simulate C input from litter production and C release through decomposition. The latter process has traditionally been represented by first-order decay functions, regulated primarily by temperature, moisture, litter quality, and soil texture. While this formulation well captures macroscopic soil organic C (SOC) dynamics, better understanding is needed of their underlying mechanisms as related to microbial processes, depth-dependent environmental controls, and other processes that strongly affect soil C dynamics. Second, incomplete use of observations in model parameterization is a major cause of bias in soil C projections from ESMs. Optimal parameter calibration with both pool- and flux-based data sets through data assimilation is among the highest priorities for near-term research to reduce biases among ESMs. Third, external variables are represented inconsistently among ESMs, leading to differences in modeled soil C dynamics. We recommend the implementation of traceability analyses to identify how external variables and model parameterizations influence SOC dynamics in different ESMs. Overall, projections of the terrestrial C sink can be substantially improved when reliable data sets are available to select the most representative model structure, constrain parameters, and prescribe forcing fields.

Global Biogeochemical Cycles↗

USGS2009

Preface

Carbon sequestration has emerged as an important option in policies to mitigate the increasing atmospheric concentrations of anthropogenic carbon dioxide (CO 2 ). Significant quantities of anthropogenic CO 2 are sequestered by natural carbon uptake in plants, soils, and the oceans. These uptake processes are objects of intense study by biogeochemists, ecologists, and other researchers who seek to understand the processes that determine the mass balance (“budget”) among global carbon fluxes. At the same time, many scientists and engineers are examining methods for deliberate carbon sequestration through storage in plants, soils, the oceans, and geological formations.

Book chapter↗

USGS2011

Tracking solutes and water from subsurface drip irrigation application of coalbed methane-produced waters, Powder River Basin, Wyoming

One method to beneficially use water produced from coalbed methane (CBM) extraction is subsurface drip irrigation (SDI) of croplands. In SDI systems, treated CBM water (injectate) is supplied to the soil at depth, with the purpose of preventing the buildup of detrimental salts near the surface. The technology is expanding within the Powder River Basin, but little research has been published on its environmental impacts. This article reports on initial results from tracking water and solutes from the injected CBM-produced waters at an SDI system in Johnson County, Wyoming. In the first year of SDI operation, soil moisture significantly increased in the SDI areas, but well water levels increased only modestly, suggesting that most of the water added was stored in the vadose zone or lost to evapotranspiration. The injectate has lower concentrations of most inorganic constituents relative to ambient groundwater at the site but exhibits a high sodium adsorption ratio. Changes in groundwater chemistry during the same period of SDI operation were small; the increase in groundwater-specific conductance relative to pre-SDI conditions was observed in a single well. Conversely, groundwater samples collected beneath another SDI field showed decreased concentrations of several constituents since the SDI operation. Groundwater-specific conductance at the 12 other wells showed no significant changes. Major controls on and compositional variability of groundwater, surface water, and soil water chemistry are discussed in detail. Findings from this research provide an understanding of water and salt dynamics associated with SDI systems using CBM-produced water.

Wyoming↗

USGS2006

Effects of water additions, chemical amendments, and plants on in situ measures of nutrient bioavailability in calcareous soils of southeastern Utah, USA

We used ion-exchange resin bags to investigate effects of water additions, chemical amendments, and plant presence on in situ measures of nutrient bioavailability in conjunction with a study examining soil controls of ecosystem invasion by the exotic annual grass Bromus tectorum L. At five dryland sites in southeastern Utah, USA, resin bags were buried in experimental plots randomly assigned to combinations of two watering treatments (wet and dry), four chemical-amendment treatments (KCl, MgO, CaO, and no amendment), and four plant treatments (B. tectorum alone, the perennial bunchgrass Stipa hymenoides R. & S. alone, B. tectorum and S. hymenoides together, and no plants). Resin bags were initially buried in September 1997; replaced in January, April, and June 1998; and removed at the end of the study in October 1998. When averaged across watering treatments, plots receiving KCl applications had lower resin-bag NO 3- than plots receiving no chemical amendments during three of four measurement periods-probably due to NO 3- displacement from resin bags by Cl- ions. During the January-April period, KCl application in wet plots (but not dry plots) decreased resin-bag NH 4+ and increased resin-bag NO 3- . This interaction effect likely resulted from displacement of NH 4+ from resins by K+ ions, followed by nitrification and enhanced NO 3- capture by resin bags. In plots not receiving KCl applications, resin-bag NH 4+ was higher in wet plots than in dry plots during the same period. During the January-April period, resin-bag measures for carbonate-related ions HPO 42- , Ca2+, and Mn2+ tended to be greater in the presence of B. tectorum than in the absence of B. tectorum. This trend was evident only in wet plots where B. tectorum densities were much higher than in dry plots. We attribute this pattern to the mobilization of carbonate-associated ions by root exudates of B. tectorum. These findings indicate the importance of considering potential indirect effects of soil amendments performed in conjunction with resource-limitation studies, and they suggest the need for further research concerning nutrient acquisition mechanisms of B. tectorum. ?? 2006 Springer Science+Business Media B.V.

Plant and Soil↗