SEARCH · Geology Reports

Results for “Soil Research”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27Linked to original sources

USGS2007

Mechanical properties of sand, silt, and clay containing tetrahydrofuran hydrate

The mechanical behavior of hydrate-bearing sediments subjected to large strains has relevance for the stability of the seafloor and submarine slopes, drilling and coring operations, and the analysis of certain small-strain properties of these sediments (for example, seismic velocities). This study reports on the results of comprehensive axial compression triaxial tests conducted at up to 1 MPa confining pressure on sand, crushed silt, precipitated silt, and clay specimens with closely controlled concentrations of synthetic hydrate. The results show that the stress-strain behavior of hydrate-bearing sediments is a complex function of particle size, confining pressure, and hydrate concentration. The mechanical properties of hydrate-bearing sediments at low hydrate concentration (probably < 40% of pore space) appear to be determined by stress-dependent soil stiffness and strength. At high hydrate concentrations (>50% of pore space), the behavior becomes more independent of stress because the hydrates control both stiffness and strength and possibly the dilative tendency of sediments by effectively increasing interparticle coordination, cementing particles together, and filling the pore space. The cementation contribution to the shear strength of hydrate-bearing sediments decreases with increasing specific surface of soil minerals. The lower the effective confining stress, the greater the impact of hydrate formation on normalized strength.

Journal of Geophysical Research B: Solid Earth↗

USGS2008

Linking soil organic matter dynamics and erosion-induced terrestrial carbon sequestration at different landform positions

Recently, the potential for terrestrial carbon (C) sequestration by soil erosion and deposition has received increased interest. Erosion and deposition constitute a sink for atmospheric carbon dioxide relative to a preerosional state or a noneroding scenario, if the posterosion watershed C balance is increased due to (1) partial replacement of eroded C by new photosynthate in the eroded site; and (2) preservation from decomposition of at least some eroded soil organic carbon (SOC) arriving in depositional settings. Little is known, however, about differences in C dynamics at different erosional and depositional landform positions within the same eroding system. We determined the contribution of different landform positions to erosion-induced terrestrial C sequestration by measuring rates of net primary productivity (NPP), replacement of eroded C, and decomposition of organic matter (OM) at four categorically different landform positions within a naturally eroding toposequence in northern California. We found that eroded C is replaced by NPP 15 times over in the summit of the site studied and 5 times over in the slope. Profile-averaged, long-term rate constant for SOM decomposition was 2 to 14 times slower in the depositional settings compared with that in eroding slopes. As a result, the inventory of C in the depositional settings was 2 to 3 times larger than that of the eroding positions. Owing to both C replacement at eroding sites and reduced rates of OM decomposition in depositional sites, soil erosion constitutes a C sink from the atmosphere at our study site.

California↗

USGS2021

Climatic controls on soil carbon accumulation and loss in a dryland ecosystems

Arid and semiarid ecosystems drive year-to-year variability in the strength of the terrestrial carbon (C) sink, yet there is uncertainty about how soil C gains and losses contribute to this variation. To address this knowledge gap, we embedded C-depleted soil mesocosms, containing litter or biocrust C inputs, within an in situ dryland ecosystem warming experiment. Over the course of one year, changes in microbial biomass and total soil organic C pools were monitored alongside hourly measurements of soil CO 2 flux. We also developed a biogeochemical model to explore the mechanisms that gave rise to observed soil C dynamics. Field data and model simulations demonstrated that water exerted much stronger control on soil biogeochemistry than temperature, with precipitation events triggering large CO 2 pulses and transport of litter- and biocrust-derived C into the soil profile. We expected leaching of organic matter would result in steady accumulation of C within the mineral soil over time. Instead, the size of the total organic C pool fluctuated throughout the year, largely in response to microbial growth: increases in the size of microbial biomass were negatively correlated with the quantity of C residing in the top 2 cm, where most biogeochemical changes were observed. Our data and models suggest that microbial responses to precipitation events trigger rapid metabolism of dissolved organic C inputs, which strongly limit accumulation of autotroph-derived C belowground. Accordingly, changes in the magnitude and/or frequency of precipitation events in this dryland ecosystem could have profound impacts on the strength of the soil C sink.

Utah↗

USGS2012

Reconnaissance techniques for determining soil-gas radon concentrations: an example from Prince Georges County, Maryland

Preliminary field measurements of soil-gas radon (Rn) concentrations can provide an initial assessment of the Rn potential in any location and aid in designing a larger or more detailed sampling program. Radon reconnaissance requires some special considerations because a large area must be covered in a short period of time and analyses must be made soon after collection because of Rn decay. A simple approach to collection and field analysis consists of a small-diameter probe pounded into the ground to a depth of at least 0.75 m. Analysis is by an alpha-scintillometer. Soil-gas samples collected along a traverse in Prince Georges County, Maryland, demonstrate the utility of the technique. Although this region in the Coastal Plain province might be considered to possess the type of geologic setting that would not contribute to significant Rn potential, the reconnaissance sampling revealed Rn soil-gas concentrations of up to 2500 pCi/L (picocuries per liter) indicating that the potential exists for indoor accumulations in excess of 4 pCi/L.

Geophysical Research Letters↗

USGS1976

A portable helium sniffer

A portable helium sniffer has been developed for field use. The instrument is mounted in a four-wheel-drive pickup truck and can detect 50 parts per billion of helium in soil gas. The usefulness of helium sniffing in soil is being investigated as a prospecting tool in gas, oil, uranium, and geothermal prospecting as well as in earthquake prediction.

Journal of Research of the U.S. Geological Survey↗

USGS2017

Mechanisms of nitrogen deposition effects on temperate forest lichens and trees

We review the mechanisms of deleterious nitrogen (N) deposition impacts on temperate forests, with a particular focus on trees and lichens. Elevated anthropogenic N deposition to forests has varied effects on individual organisms depending on characteristics both of the N inputs (form, timing, amount) and of the organisms (ecology, physiology) involved. Improved mechanistic knowledge of these effects can aid in developing robust predictions of how organisms respond to either increases or decreases in N deposition. Rising N levels affect forests in micro- and macroscopic ways from physiological responses at the cellular, tissue, and organism levels to influencing individual species and entire communities and ecosystems. A synthesis of these processes forms the basis for the overarching themes of this paper, which focuses on N effects at different levels of biological organization in temperate forests. For lichens, the mechanisms of direct effects of N are relatively well known at cellular, organismal, and community levels, though interactions of N with other stressors merit further research. For trees, effects of N deposition are better understood for N as an acidifying agent than as a nutrient; in both cases, the impacts can reflect direct effects on short time scales and indirect effects mediated through long-term soil and belowground changes. There are many gaps on fundamental N use and cycling in ecosystems, and we highlight the most critical gaps for understanding potential deleterious effects of N deposition. For lichens, these gaps include both how N affects specific metabolic pathways and how N is metabolized. For trees, these gaps include understanding the direct effects of N deposition onto forest canopies, the sensitivity of different tree species and mycorrhizal symbionts to N, the influence of soil properties, and the reversibility of N and acidification effects on plants and soils. Continued study of how these N response mechanisms interact with one another, and with other dimensions of global change, remains essential for predicting ongoing changes in lichen and tree populations across North American temperate forests.

Ecosphere↗

USGS2019

Contemporary human impacts on alpine ecosystems: the direct and indirect effects of human-induced climate change and land use

Alpine ecosystems account for ca. 3 % of terrestrial habitats yet, along with adjacent mountain systems, provide water resources to nearly half of the world’s human population. Approximately 20 % of humans live in or near mountain areas, making it inherently important to understand current impacts on these systems. Here, I review literature regarding current and projected human impacts on alpine ecosystems, including the direct and indirect impacts of human-induced climate change on alpine plant, animal, and soil communities. I also discuss the influence of recreation and tourism, grazing, and other land use changes including the introduction of non-native and invasive species in alpine systems. I conclude with management implications as well as future areas of research needed to better understand changes to these systems.

Book chapter↗

USGS2007

Monitoring post-fire vegetation rehabilitation projects: A common approach for non-forested ecosystems

Emergency Stabilization and Rehabilitation (ES&R) and Burned Area Emergency Response (BAER) treatments are short-term, high-intensity treatments designed to mitigate the adverse effects of wildfire on public lands. The federal government expends significant resources implementing ES&R and BAER treatments after wildfires; however, recent reviews have found that existing data from monitoring and research are insufficient to evaluate the effects of these activities. The purpose of this report is to: (1) document what monitoring methods are generally used by personnel in the field; (2) describe approaches and methods for post-fire vegetation and soil monitoring documented in agency manuals; (3) determine the common elements of monitoring programs recommended in these manuals; and (4) describe a common monitoring approach to determine the effectiveness of future ES&R and BAER treatments in non-forested regions. Both qualitative and quantitative methods to measure effectiveness of ES&R treatments are used by federal land management agencies. Quantitative methods are used in the field depending on factors such as funding, personnel, and time constraints. There are seven vegetation monitoring manuals produced by the federal government that address monitoring methods for (primarily) vegetation and soil attributes. These methods vary in their objectivity and repeatability. The most repeatable methods are point-intercept, quadrat-based density measurements, gap intercepts, and direct measurement of soil erosion. Additionally, these manuals recommend approaches for designing monitoring programs for the state of ecosystems or the effect of management actions. The elements of a defensible monitoring program applicable to ES&R and BAER projects that most of these manuals have in common are objectives, stratification, control areas, random sampling, data quality, and statistical analysis. The effectiveness of treatments can be determined more accurately if data are gathered using an approach that incorporates these six monitoring program design elements and objectives, as well as repeatable procedures to measure cover, density, gap intercept, and soil erosion within each ecoregion and plant community. Additionally, using a common monitoring program design with comparable methods, consistently documenting results, and creating and maintaining a central database for query and reporting, will ultimately allow a determination of the effectiveness of post-fire rehabilitation activities region-wide.

Scientific Investigations Report↗

USGS2008

Portable chamber measurements of evapotranspiration at the Amargosa Desert Research Site near Beatty, Nye County, Nevada, 2003-06

Portable chamber measurements of evapotranspiration (ET) were made at the U.S. Geological Survey's Amargosa Desert Research Site in southern Nevada to help quantify component- and landscape-scale contributions to ET in an arid environment. Evapotranspiration data were collected approximately every 3 months from 2003 to 2006. Chamber measurements of ET were partitioned into bare-soil evaporation and mixed-species transpiration components. The component-scale ET fluxes from native shrubs typically surpassed those from bare soil by as much as a factor of four. Component-scale ET fluxes were extrapolated to landscape-scale ET using a one-layer, multi-component canopy model. Landscape-scale ET fluxes predominantly were controlled by bare-soil evaporation. Bare soil covered 94 percent of the landscape on average and contributed about 70 percent of the landscape-scale vapor flux. Creosote bush, an evergreen shrub, accounted for about 90 percent of transpiration on average due to its dominance across the landscape (80 percent of the 6 percent shrub cover) and evergreen character.

Nevada↗

USGS2009

Responses of stream nitrate and dissolved organic carbon loadings to hydrological forcing and climate change in an upland forest of the northeast USA

[1] In coming decades, higher annual temperatures, increased growing season length, and increased dormant season precipitation are expected across the northeastern United States in response to anthropogenic forcing of global climate. We synthesized long-term stream hydrochemical data from the Sleepers River Research Watershed in Vermont, United States, to explore the relationship of catchment wetness to stream nitrate and DOC loadings. We modeled changes in growing season length and precipitation patterns to simulate future climate scenarios and to assess how stream nutrient loadings respond to climate change. Model results for the 2070–2099 time period suggest that stream nutrient loadings during both the dormant and growing seasons will respond to climate change. During a warmer climate, growing season stream fluxes (runoff +20%, nitrate +57%, and DOC +58%) increase as more precipitation (+28%) and quick flow (+39%) occur during a longer growing season (+43 days). During the dormant season, stream water and nutrient loadings decrease. Net annual stream runoff (+8%) and DOC loading (+9%) increases are commensurate with the magnitude of the average increase of net annual precipitation (+7%). Net annual stream water and DOC loadings are primarily affected by increased dormant season precipitation. In contrast, decreased annual loading of stream nitrate (−2%) reflects a larger effect of growing season controls on stream nitrate and the effects of lengthened growing seasons in a warmer climate. Our findings suggest that leaching of nitrate and DOC from catchment soils will be affected by anthropogenic climate forcing, thereby affecting the timing and magnitude of annual stream loadings in the northeastern United States.

Vermont↗

USGS1963

Specific Yield--Column drainage and centrifuge moisture content

The specific yield of a rock or soil, with respect to water, is the ratio of (1) the volume of water which, after being saturated, it will yield by gravity to (2) its own volume. Specific retention represents the water retained against gravity drainage. The specific yield and retention when added together are equal to the total interconnected porosity of the rock or soil. Because specific retention is more easily determined than specific yield, most methods for obtaining yield first require the determination of specific retention. Recognizing the great need for developing improved methods of determining the specific yield of water-bearing materials, the U.S. Geological Survey and the California Department of Water Resources initiated a cooperative investigation of this subject. The major objectives of this research are (1) to review pertinent literature on specific yield and related subjects, (2) to increase basic knowledge of specific yield and rate of drainage and to determine the most practical methods of obtaining them, (3) to compare and to attempt to correlate the principal laboratory and field methods now commonly used to obtain specific yield, and (4) to obtain improved estimates of specific yield of water-bearing deposits in California. An open-file report, 'Specific yield of porous media, an annotated bibliography,' by A. I. Johnson, D. A. Morris, and R. C. Prill, was released in 1960 in partial fulfillment of the first objective. This report describes the second phase of the specific-yield study by the U.S. Geological Survey Hydrologic Laboratory at Denver, Colo. Laboratory research on column drainage and centrifuge moisture equivalent, two methods for estimating specific retention of porous media, is summarized. In the column-drainage study, a wide variety of materials was packed into plastic columns of 1- to 8-inch diameter, wetted with Denver tap water, and drained under controlled conditions of temperature and humidity. The effects of cleaning the porous media; of different column diameters; of dye and time on drainage; and of different methods of drainage, wetting, and packing were all determined. To insure repeatability of porosity in duplicate columns, a mechanical technique of packing was developed. In the centrifuge moisture-content study, the centrifuge moisture-equivalent (the moisture content retained by a soil that has been first saturated and then subjected to a force equal to 1,000 times the force of gravity for 1 hour) test was first reviewed and evaluated. It was determined that for reproducible moisture-retention results the temperature and humidity should be controlled by use of a controlled-temperature centrifuge. In addition to refining this standard test, the study determined the effect of length of period of centrifuging and of applied tension on the drainage results. The plans for future work require the continuation of the laboratory standardization study qith emphasis on investigation of soil-moisture tension and unsaturated-permeability techniques. A detailed study in the field then will be followed by correlation and evaluation of laboratory and field methods.

Water Supply Paper↗

USGS2015

Source limitation of carbon gas emissions in high-elevation mountain streams and lakes

Inland waters are an important component of the global carbon cycle through transport, storage, and direct emissions of CO 2 and CH 4 to the atmosphere. Despite predictions of high physical gas exchange rates due to turbulent flows and ubiquitous supersaturation of CO 2 —and perhaps also CH 4 —patterns of gas emissions are essentially undocumented for high mountain ecosystems. Much like other headwater networks around the globe, we found that high-elevation streams in Rocky Mountain National Park, USA, were supersaturated with CO 2 during the growing season and were net sources to the atmosphere. CO 2 concentrations in lakes, on the other hand, tended to be less than atmospheric equilibrium during the open water season. CO 2 and CH 4 emissions from the aquatic conduit were relatively small compared to many parts of the globe. Irrespective of the physical template for high gas exchange (high k ), we found evidence of CO 2 source limitation to mountain streams during the growing season, which limits overall CO 2 emissions. Our results suggest a reduced importance of aquatic ecosystems for carbon cycling in high-elevation landscapes having limited soil development and high CO 2 consumption via mineral weathering.

Journal of Geophysical Research G: Biogeosciences↗

USGS2008

Boreal soil carbon dynamics under a changing climate: A model inversion approach

Several fundamental but important factors controlling the feedback of boreal organic carbon (OC) to climate change were examined using a mechanistic model of soil OC dynamics, including the combined effects of temperature and moisture on the decomposition of OC and the factors controlling carbon quality and decomposition with depth. To estimate decomposition rates and evaluate their variations with depth, the model was inverted using a global optimization algorithm. Three sites with different drainage conditions that represent a broad diversity of boreal black spruce ecosystems were modeled. The comparison among the models with different depth patterns of decomposition rates (i.e., constant, linear, and exponential decrease) revealed that the model with constant inherent decomposition rates through the soil profile was able to fit the observed data in the most efficient way. There were also lower turnover times in the wettest site compared to the drier site even after accounting for moisture and temperature differences. Taken together, these results indicate that decomposition (especially for the wetter site) was not accurately represented with standard moisture and temperature controls and that other important protection mechanisms (e.g., limitation of O 2 , redox conditions, and permafrost) rather than low inherent decomposition rates are responsible for the recalcitrance of deep OC. The simulation results also showed that most of the soil CO 2 efflux is generated from subsurface layers of OC because of the large OC stocks and optimal moisture conditions, suggesting that these deeper soil OC stocks are likely to be critically important to the future carbon dynamics.

Journal of Geophysical Research Biogeosciences↗

USGS2023

Can hydrological models benefit from using global soil moisture, evapotranspiration, and runoff products as calibration targets?

Hydrological models are usually calibrated to in-situ streamflow observations with reasonably long and uninterrupted records. This is challenging for poorly gage or ungaged basins where such information is not available. Even for gaged basins, the single-objective calibration to gaged streamflow cannot guarantee reliable forecasts because, as has been documented elsewhere, the inverse problem is mathematically ill-posed. Therefore, the inclusion of other observations, and the reproduction of other hydrological variables beyond streamflow, become critical components of accurate hydrological forecasting. In this study, six single- and multi-objective model calibration schemes based on different combinations of gaged streamflow, global-scale gridded soil moisture, actual evapotranspiration (ET), and runoff products are used for the calibration of a process-based hydrological model for 20 catchments located within the Lake Michigan watershed, of the Laurentian Great Lakes. Results show that the addition of gridded soil moisture to gaged streamflow in model calibration improves the ET simulation performance for most of the catchments, leading to the overall best-performing models. The monthly streamflow simulation performance for the experiments using gridded runoff products to inform the model is outperformed by those using the gaged streamflow, but the discrepancy is mitigated with increasing catchment scale. A new visualization method that effectively synthesizes model performance for the simulations of streamflow, soil moisture, and ET was also proposed. Based on the method, it is revealed that the streamflow simulation performance is relatively weak for baseflow-dominated catchments; overall, the 20 catchment models simulate streamflow and ET better than soil moisture.

Lake Michigan↗

USGS2025

Experimental warming alters free-living nitrogen fixation in a humid tropical forest

Microbial nitrogen (N) fixation accounts for c. 97% of natural N inputs to terrestrial ecosystems. These microbes can be free-living in the soil and leaf litter (asymbiotic) or in symbiosis with plants. Warming is expected to increase N-fixation rates because warmer temperatures favor the growth and activity of N-fixing microbes. We investigated the effects of warming on asymbiotic components of N fixation at a field warming experiment in Puerto Rico. We analyzed the function and composition of bacterial communities from surface soil and leaf litter samples. Warming significantly increased asymbiotic N-fixation rates in soil by 55% (to 0.002 kg ha −1 yr −1 ) and by 525% in leaf litter (to 14.518 kg ha −1 yr −1 ) . This increase in N fixation was associated with changes in the N-fixing bacterial community composition and soil nutrients. Our findings suggest that warming increases the natural N inputs from the atmosphere into this tropical forest due to changes in microbial function and composition, especially in the leaf litter. Given the importance of leaf litter in nutrient cycling, future research should investigate other aspects of N cycles in the leaf litter under warming conditions.

Luquillo Experimental Forest, northeastern Puerto ↗

USGS2009

Effects of an invasive plant species, celastrus orbiculatus, on soil composition and processes

Celastrus orbiculatus is a non-native, invasive liana that was introduced to the United States in the 1860s and has spread rapidly throughout the Northeast Several attributes contribute to the invasiveness of C. orbiculatus, including tolerance to a wide range of light levels and habitat types. We compared soil characteristics in seven sets of adjacent, paired plots, spanning a range of habitats and soil types, with and without C. orbiculatus. The paired plots were similar other than the presence or absence of Celastrus. Plots with C. orbiculatus had significantly higher soil pH, potassium, calcium and magnesium levels. Furthermore, nitrogen mineralization and litter decomposition rates were higher in plots with C. orbiculatus. Phosphorus levels were not significantly different between the paired plots. The results of this study contribute to the growing body of research of the effects of invasive species on ecosystem processes.

American Midland Naturalist↗

USGS2012

Geologic map of the Great Smoky Mountains National Park region, Tennessee and North Carolina

The geology of the Great Smoky Mountains National Park region of Tennessee and North Carolina was studied from 1993 to 2003 as part of a cooperative investigation by the U.S. Geological Survey with the National Park Service (NPS). This work resulted in a 1:100,000-scale geologic map derived from mapping that was conducted at scales of 1:24,000 and 1:62,500. The geologic data are intended to support cooperative investigations with the NPS, the development of a new soil map by the Natural Resources Conservation Service, and the All Taxa Biodiversity Inventory. In response to a request by the NPS, we mapped previously unstudied areas, revised the geology where problems existed, and developed a map database for use in interdisciplinary research, land management, and interpretive programs for park visitors.

North Carolina, Tennessee↗

USGS1966

Monitoring wildlife for pesticide content

In May 1963, the President's Science Advisory Committee issued a report entitled Use of Pesticides . 17 the President already had requested the responsible federal agencies to implement the recommendations in the report. One of these recommendations was to provide for the development and coordination of a pesticide-monitoring program conducted on a continuing basis, by federal agencies to obtain timely systematic data on pesticide residues in the environment. Many people re engaged in research to learn the quantities of pesticide that may be hazardous. Yet there is concern that hazardous quantities may accumulate before the difficult task of evaluation can be completed. The President's report on environmental pollution 12 expresses the view that the soils and waters of the world cannot indefinitely provide a vast dumping ground to absorb and render harmless all human wastes. Chlorinated hydrocarbon pesticides are only one of these kinds of pollutants, yet they are particularly important because they persist long in the environment and accumulate in the tissues of animals.

National Academy of Sciences NRC Publication↗