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At least 1,009 records · Page 56Linked to original sources
USGS2019

The long-term effects of Hurricanes Wilma and Irma on soil elevation change in Everglades mangrove forests

Mangrove forests in the Florida Everglades (USA) are frequently affected by hurricanes that produce high-velocity winds, storm surge, and extreme rainfall, but also provide sediment subsidies that help mangroves adjust to sea-level rise. The long-term influence of hurricane sediment inputs on soil elevation dynamics in mangrove forests are not well understood. Here, we assessed the effects of sediment deposition during Hurricanes Wilma (2005) and Irma (2017) on soil elevation change at two mangrove forests located along the Shark and Lostmans Rivers in Everglades National Park. We used surface elevation change data from a sixteen-year period (2002-2018), measured with the surface elevation table-marker horizon (SET-MH) approach. At the Shark River mangrove forest, we used marker horizons and a combination of deep, shallow, and original SETs to quantify the contributions of four soil zones to net soil elevation change. Rates of elevation change were greatly influenced by storm sediments. Abrupt increases in elevation due to sediment inputs and subsurface expansion during Hurricane Wilma were followed by: (1) an initial post-hurricane period of elevation loss due to erosion of hurricane sediments and subsurface contraction; (2) a secondary period of elevation gain due primarily to accretion; and (3) an abrupt elevation gain due to new sediment inputs during Hurricane Irma. Our findings suggest that elevation change in hurricane-affected mangrove forests can be cyclical or include disjunct phases, which is critical information for advancing the understanding of wetland responses to accelerated sea-level rise given the expectation of increasing storm intensity due to climate change.

Florida↗
USGS2011

Effects of soil-engineering properties on the failure mode of shallow landslides

Some landslides mobilize into flows, while others slide and deposit material immediately down slope. An index based on initial dry density and fine-grained content of soil predicted failure mode of 96 landslide initiation sites in Oregon and Colorado with 79% accuracy. These material properties can be used to identify potential sources for debris flows and for slides. Field data suggest that loose soils can evolve from dense soils that dilate upon shearing. The method presented herein to predict failure mode is most applicable for shallow (depth <5 m), well-graded soils (coefficient of uniformity >8), with few to moderate fines (fine-grained content <18%), and with liquid limits <40.

Landslides↗
USGS2012

The effect of increasing salinity and forest mortality on soil nitrogen and phosphorus mineralization in tidal freshwater forested wetlands

Tidal freshwater wetlands are sensitive to sea level rise and increased salinity, although little information is known about the impact of salinification on nutrient biogeochemistry in tidal freshwater forested wetlands. We quantified soil nitrogen (N) and phosphorus (P) mineralization using seasonal in situ incubations of modified resin cores along spatial gradients of chronic salinification (from continuously freshwater tidal forest to salt impacted tidal forest to oligohaline marsh) and in hummocks and hollows of the continuously freshwater tidal forest along the blackwater Waccamaw River and alluvial Savannah River. Salinification increased rates of net N and P mineralization fluxes and turnover in tidal freshwater forested wetland soils, most likely through tree stress and senescence (for N) and conversion to oligohaline marsh (for P). Stimulation of N and P mineralization by chronic salinification was apparently unrelated to inputs of sulfate (for N and P) or direct effects of increased soil conductivity (for N). In addition, the tidal wetland soils of the alluvial river mineralized more P relative to N than the blackwater river. Finally, hummocks had much greater nitrification fluxes than hollows at the continuously freshwater tidal forested wetland sites. These findings add to knowledge of the responses of tidal freshwater ecosystems to sea level rise and salinification that is necessary to predict the consequences of state changes in coastal ecosystem structure and function due to global change, including potential impacts on estuarine eutrophication.

Biogeochemistry↗
USGS2013

Soil criteria to protect terrestrial wildlife and open-range livestock from metal toxicity at mining sites

Thousands of hard rock mines exist in the western USA and in other parts of the world as a result of historic and current gold, silver, lead, and mercury mining. Many of these sites in the USA are on public lands. Typical mine waste associated with these sites are tailings and waste rock dumps that may be used by wildlife and open-range livestock. This report provides wildlife screening criteria levels for metals in soil and mine waste to evaluate risk and to determine the need for site-specific risk assessment, remediation, or a change in management practices. The screening levels are calculated from toxicity reference values based on maximum tolerable levels of metals in feed, on soil and plant ingestion rates, and on soil to plant uptake factors for a variety of receptors. The metals chosen for this report are common toxic metals found at mining sites: arsenic, cadmium, copper, lead, mercury, and zinc. The resulting soil screening values are well above those developed by the US Environmental Protection Agency. The difference in values was mainly a result of using toxicity reference values that were more specific to the receptors addressed rather than the most sensitive receptor.

Environmental Monitoring and Assessment↗
USGS2006

Evaluating the relative contributions of hydroperiod and soil fertility on growth of south Florida mangroves

Low and high water periods create contrasting challenges for trees inhabiting periodically flooded wetlands. Low to moderate flood durations and frequencies may bring nutrient subsidies, while greater hydroperiods can be energetically stressful because of oxygen deficiency. We tested the hypothesis that hydroperiod affects the growth of mangrove seedlings and saplings in a greenhouse experiment by varying flood duration while keeping salinity and soil fertility constant. We measured the growth of mangrove trees along a hydroperiod gradient over a two-year period by tracking fine-scale diameter increment. Greenhouse growth studies indicated that under a full range of annual flood durations (0-8760 h/year), hydroperiod alone exerted a significant influence on growth for one species, Laguncularia racemosa, when flooding was imposed for two growing seasons. Field evaluations, on the other hand, indicated that increased flood duration may provide nutrient subsidies for tree growth. Diameter growth was related curvilinearly to site hydroperiod, including flood duration and frequency, as well as to salinity and soil fertility. An analysis of soil physico-chemical parameters suggests that phosphorus fertility, which was also linked directly to hydroperiod, is likely to influence growth on south Florida mangrove sites. The physical removal of phosphorus by greater flood frequencies from upland sources and/or addition of phosphorus from tidal flooding balanced against increased soil aeration and reduced water deficits may be an extremely important growth determinant for south Florida mangroves. ?? Springer 2006.

Hydrobiologia↗
USGS2011

Development of soil properties and nitrogen cycling in created wetlands

Mitigation wetlands are expected to compensate for the loss of structure and function of natural wetlands within 5–10 years of creation; however, the age-based trajectory of development in wetlands is unclear. This study investigates the development of coupled structural (soil properties) and functional (nitrogen cycling) attributes of created non-tidal freshwater wetlands of varying ages and natural reference wetlands to determine if created wetlands attain the water quality ecosystem service of nitrogen (N) cycling over time. Soil condition component and its constituents, gravimetric soil moisture, total organic carbon, and total N, generally increased and bulk density decreased with age of the created wetland. Nitrogen flux rates demonstrated age-related patterns, with younger created wetlands having lower rates of ammonification, nitrification, nitrogen mineralization, and denitrification potential than older created wetlands and natural reference wetlands. Results show a clear age-related trajectory in coupled soil condition and N cycle development, which is essential for water quality improvement. These findings can be used to enhance N processing in created wetlands and inform the regulatory evaluation of mitigation wetlands by identifying structural indicators of N processing performance.

Wetlands↗
USGS2019

Can multi-element fingerprinting of soils inform assessments of chemical connectivity between depressional wetlands?

The question of wetland connectivity is particularly relevant regarding depressional wetlands because these wetlands often seem to be “isolated” from other wetlands on a landscape. In this study, multi-element fingerprinting of soils was used to assess similarity in element composition of depressional-wetland soils as a measure of wetland connectivity. We determined the concentrations of 63 elements in the surface soil (top 10 cm) for ten sequences, each consisting of at least one recharge, one flow-through and one discharge depressional wetland in the Prairie Pothole Region of North Dakota. Across all wetlands, soil pH, organic matter content, and electrical conductivity were the most important variables explaining variation in element concentrations. Electrical conductivity and pH significantly increased along a recharge to flow-through to discharge gradient, as did concentrations of As, B, Ca, Co, Hf, Li, Mg, Na, S, Sb, and Sr. Concentrations of Ag, Cd, Cu, P, Pb, Rb, and Se showed the reverse pattern. Similarity-tree analysis revealed that recharge and discharge wetlands clustered in different groups, but that flow-through wetlands were distributed across the spectrum. Our study supports the idea that wetlands in the PPR are chemically connected through surface-water and groundwater flows, and erosional processes, but also behave as independent units within a larger hydrologic landscape.

North Dakota↗
USGS2022

From data to interpretable models: Machine learning for soil moisture forecasting

Soil moisture is critical to agricultural business, ecosystem health, and certain hydrologically driven natural disasters. Monitoring data, though, is prone to instrumental noise, wide ranging extrema, and nonstationary response to rainfall where ground conditions change. Furthermore, existing soil moisture models generally forecast poorly for time periods greater than a few hours. To improve such forecasts, we introduce two data-driven models, the Naive Accumulative Representation (NAR) and the Additive Exponential Accumulative Representation (AEAR). Both of these models are rooted in deterministic, physically based hydrology, and we study their capabilities in forecasting soilmoisture over time periods longer than a fewhours. Learned model parameters represent the physically based unsaturated hydrological redistribution processes of gravity and suction. We validate our models using soil moisture and rainfall time series data collected from a steep gradient, post-wildfire site in southern California. Data analysis is complicated by rapid landscape change observed in steep, burned hillslopes in response to even small to moderate rain events. The proposed NAR and AEAR models are, in forecasting experiments, shown to be competitive with several established and state-of-the-art baselines. The AEAR model fits the data well for three distinct soil textures at variable depths below the ground surface (5, 15, and 30 cm). Similar robust results are demonstrated in controlled, laboratory-based experiments. Our AEAR model includes readily interpretable hydrologic parameters and provides more accurate forecasts than existing models for time horizons of 10–24 h. Such extended periods of warning for natural disasters, such as floods and landslides, provide actionable knowledge to reduce loss of life and property.

International Journal of Data Science and Analytic↗
USGS2009

Airborne gamma-ray and magnetic anomaly signatures of serpentinite in relation to soil geochemistry, northern California

Serpentinized ultramafic rocks and associated soils in northern California are characterized by high concentrations of Cr and Ni, low levels of radioelements (K, Th, and U) and high amounts of ferrimagnetic minerals (primarily magnetite). Geophysical attributes over ultramafic rocks, which include airborne gamma-ray and magnetic anomaly data, are quantified and provide indirect measurements on the relative abundance of radioelements and magnetic minerals, respectively. Attributes are defined through a statistical modeling approach and the results are portrayed as probabilities in chart and map form. Two predictive models are presented, including one derived from the aeromagnetic anomaly data and one from a combination of the airborne K, Th and U gamma-ray data. Both models distinguish preferential values within the aerogeophysical data that coincide with mapped and potentially unmapped ultramafic rocks. The magnetic predictive model shows positive probabilities associated with magnetic anomaly highs and, to a lesser degree, anomaly lows, which accurately locate many known ultramafic outcrops, but more interestingly, locate potentially unmapped ultramafic rocks, possible extensions of ultramafic bodies that dip into the shallow subsurface, as well as prospective buried ultramafic rocks. The airborne radiometric model shows positive probabilities in association with anomalously low gamma radiation measurements over ultramafic rock, which is similar to that produced by gabbro, metavolcanic rock, and water bodies. All of these features share the characteristic of being depleted in K, Th and U. Gabbro is the only rock type in the study area that shares similar magnetic properties with the ultramafic rock. The aerogeophysical model results are compared to the distribution of ultramafic outcrops and to Cr, Ni, K, Th and U concentrations and magnetic susceptibility measurements from soil samples. Analysis of the soil data indicates high positive correlation between magnetic susceptibilities and concentration of Cr and Ni. Although the study focused on characterizing the geophysical properties of ultramafic rocks and associated soils, it has also yielded information on other rock types in addition to ultramafic rocks, which can also locally host naturally-occurring asbestos; specifically, gabbro and metavolcanic rocks.

Applied Geochemistry↗
USGS2011

Responses of soil and water chemistry to mountain pine beetle induced tree mortality in Grand County, Colorado, USA

Pine forest in northern Colorado and southern Wyoming, USA, are experiencing the most severe mountain pine beetle epidemic in recorded history, and possible degradation of drinking-water quality is a major concern. The objective of this study was to investigate possible changes in soil and water chemistry in Grand County, Colorado in response to the epidemic, and to identify major controlling influences on stream-water nutrients and C in areas affected by the mountain pine beetle. Soil moisture and soil N increased in soils beneath trees killed by the mountain pine beetle, reflecting reduced evapotranspiration and litter accumulation and decay. No significant changes in stream-water NO 3 - "> NO 3 - or dissolved organic C were observed; however, total N and total P increased, possibly due to litter breakdown or increased productivity related to warming air temperatures. Multiple-regression analyses indicated that % of basin affected by mountain pine beetles had minimal influence on stream-water NO 3 - "> NO 3 - and dissolved organic C; instead, other basin characteristics, such as percent of the basin classified as forest, were much more important.

Colorado↗
USGS2011

Soil-geomorphic significance of land surface characteristics in an arid mountain range, Mojave Desert, USA

Mountains comprise an extensive and visually prominent portion of the landscape in the Mojave Desert, California. Landform surface properties influence the role these mountains have in geomorphic processes such as dust flux and surface hydrology across the region. The primary goal of this study was to describe and quantify land surface properties of arid-mountain landforms as a step toward unraveling the role these properties have in soil-geomorphic processes. As part of a larger soil-geomorphic study, four major landform types were identified within the southern Fry Mountains in the southwestern Mojave Desert on the basis of topography and landscape position: mountaintop, mountainflank, mountainflat (intra-range low-relief surface), and mountainbase. A suite of rock, vegetation, and morphometric land surface characteristic variables was measured at each of 65 locations across the study area, which included an associated piedmont and playa. Our findings show that despite the variation within types, landforms have distinct land surface properties that likely control soil-geomorphic processes. We hypothesize that surface expression influences a feedback process at this site where water transports sediment to low lying areas on the landscape and wind carries dust and soluble salts to the mountains where they are washed between rocks, incorporated into the soil, and retained as relatively long-term storage. Recent land-based video and satellite photographs of the dust cloud emanating from the Sierra Cucapá Mountains in response to the 7.2-magnitude earthquake near Mexicali, Mexico, support the hypothesis that these landforms are massive repositories of dust.

Mojave Desert↗
USGS2011

A mass-balance model to separate and quantify colloidal and solute redistributions in soil

Studies of weathering and pedogenesis have long used calculations based upon low solubility index elements to determine mass gains and losses in open systems. One of the questions currently unanswered in these settings is the degree to which mass is transferred in solution (solutes) versus suspension (colloids). Here we show that differential mobility of the low solubility, high field strength (HFS) elements Ti and Zr can trace colloidal redistribution, and we present a model for distinguishing between mass transfer in suspension and solution. The model is tested on a well-differentiated granitic catena located in Kruger National Park, South Africa. Ti and Zr ratios from parent material, soil and colloidal material are substituted into a mixing equation to quantify colloidal movement. The results show zones of both colloid removal and augmentation along the catena. Colloidal losses of 110kgm-2 (-5% relative to parent material) are calculated for one eluviated soil profile. A downslope illuviated profile has gained 169kgm-2 (10%) colloidal material. Elemental losses by mobilization in true solution are ubiquitous across the catena, even in zones of colloidal accumulation, and range from 1418kgm-2 (-46%) for an eluviated profile to 195kgm-2 (-23%) at the bottom of the catena. Quantification of simultaneous mass transfers in solution and suspension provide greater specificity on processes within soils and across hillslopes. Additionally, because colloids include both HFS and other elements, the ability to quantify their redistribution has implications for standard calculations of soil mass balances using such index elements. ?? 2011.

Chemical Geology↗
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↗
USGS2015

Sea level and turbidity controls on mangrove soil surface elevation change

Increases in sea level are a threat to seaward fringing mangrove forests if levels of inundation exceed the physiological tolerance of the trees; however, tidal wetlands can keep pace with sea level rise if soil surface elevations can increase at the same pace as sea level rise. Sediment accretion on the soil surface and belowground production of roots are proposed to increase with increasing sea level, enabling intertidal habitats to maintain their position relative to mean sea level, but there are few tests of these predictions in mangrove forests. Here we used variation in sea level and the availability of sediments caused by seasonal and inter-annual variation in the intensity of La Nina-El Nino to assess the effects of increasing sea level on surface elevation gains and contributing processes (accretion on the surface, subsidence and root growth) in mangrove forests. We found that soil surface elevation increased with mean sea level (which varied over 250 mm during the study) and with turbidity at sites where fine sediment in the water column is abundant. In contrast, where sediments were sandy, rates of surface elevation gain were high, but not significantly related to variation in turbidity, and were likely to be influenced by other factors that deliver sand to the mangrove forest. Root growth was not linked to soil surface elevation gains, although it was associated with reduced shallow subsidence, and therefore may contribute to the capacity of mangroves to keep pace with sea level rise. Our results indicate both surface (sedimentation) and subsurface (root growth) processes can influence mangrove capacity to keep pace with sea level rise within the same geographic location, and that current models of tidal marsh responses to sea level rise capture the major feature of the response of mangroves where fine, but not coarse, sediments are abundant.

Estuarine, Coastal and Shelf Science↗
USGS2018

Ghost forests of Marco Island: Mangrove mortality driven by belowground soil structural shifts during tidal hydrologic alteration

Land use changes often create in situ stress and eventual mortality in mangroves as unsuitable hydroperiods are created through tidal flow alterations. Here, we document mangrove forest and soil structural changes within transects established in tidally restricted areas on Marco Island (Collier County, Florida, USA), which has broad swaths of dead-standing or unhealthy mangroves (“ghost forests”). Transects (N = 4) were arranged to include full canopy, transitional, and open canopy (dead) forests, and compared to nearby reference forests. Aboveground and belowground carbon (C) stocks (Total C) ranged from 288 to 304 Mg C ha −1 on full canopy, transitional, and reference sites, which did not differ from each other. However, Total C was lower for dead sites (233 Mg C ha −1 ) dictated entirely by differences in aboveground C (live and dead trees, downed wood); no differences were found among forest condition in belowground C stocks. This belowground C has been persistent in the soil for 85 years since initial tidal restriction. Nevertheless, hydrologic rehabilitation has the potential to increase total C stocks on dead sites by 70–110 Mg C ha −1 . Collapse of the soil surface by 6–8 cm just under the active root zone in chronically stressed mangroves was evident within the bulk density profiles from transitional versus dead sites, suggesting that surface elevation loss as root turnover ceases may work correlatively with chronic stressors (anoxia, P limitation) to affect rapid mortality of forests over short periods of time many years after stress initiation. Hydrologic rehabilitation of stressed or denuded mangroves must also include an understanding of how these soil processes might be re-established.

Florida↗
USGS2006

One-day rate measurements for estimating net nitrification potential in humid forest soils

Measurements of net nitrification rates in forest soils have usually been performed by extended sample incubation (2-8 weeks), either in the field or in the lab. Because of disturbance effects, these measurements are only estimates of nitrification potential and shorter incubations may suffice. In three separate studies of northeastern USA forest soil surface horizons, we found that laboratory nitrification rates measured over 1 day related well to those measured over 4 weeks. Soil samples of Oa or A horizons were mixed by hand and the initial extraction of subsamples, using 2 mol L-1 KCl, occurred in the field as soon as feasible after sampling. Soils were kept near field temperature and subsampled again the following day in the laboratory. Rates measured by this method were about three times higher than the 4-week rates. Variability in measured rates was similar over either incubation period. Because NO3- concentrations were usually quite low in the field, average rates from 10 research watersheds could be estimated with only a single, 1-day extraction. Methodological studies showed that the concentration of NH4+ increased slowly during contact time with the KCl extractant and, thus, this contact time should be kept similar during the procedure. This method allows a large number of samples to be rapidly assessed. ?? 2006 Elsevier B.V. All rights reserved.

Forest Ecology and Management↗
USGS2016

POLARIS: A 30-meter probabilistic soil series map of the contiguous United States

A new complete map of soil series probabilities has been produced for the contiguous United States at a 30 m spatial resolution. This innovative database, named POLARIS, is constructed using available high-resolution geospatial environmental data and a state-of-the-art machine learning algorithm (DSMART-HPC) to remap the Soil Survey Geographic (SSURGO) database. This 9 billion grid cell database is possible using available high performance computing resources. POLARIS provides a spatially continuous, internally consistent, quantitative prediction of soil series. It offers potential solutions to the primary weaknesses in SSURGO: 1) unmapped areas are gap-filled using survey data from the surrounding regions, 2) the artificial discontinuities at political boundaries are removed, and 3) the use of high resolution environmental covariate data leads to a spatial disaggregation of the coarse polygons. The geospatial environmental covariates that have the largest role in assembling POLARIS over the contiguous United States (CONUS) are fine-scale (30 m) elevation data and coarse-scale (~ 2 km) estimates of the geographic distribution of uranium, thorium, and potassium. A preliminary validation of POLARIS using the NRCS National Soil Information System (NASIS) database shows variable performance over CONUS. In general, the best performance is obtained at grid cells where DSMART-HPC is most able to reduce the chance of misclassification. The important role of environmental covariates in limiting prediction uncertainty suggests including additional covariates is pivotal to improving POLARIS' accuracy. This database has the potential to improve the modeling of biogeochemical, water, and energy cycles in environmental models; enhance availability of data for precision agriculture; and assist hydrologic monitoring and forecasting to ensure food and water security.

Geoderma↗
USGS2025

Seasonal increases in global dryland gross primary production are modulated by root soil moisture and temperature

Dryland ecosystems, which are highly sensitive to environmental variability across space and through time, play a critical role in the global carbon cycle. To understand the carbon sink role of drylands, this study used different sources of global dryland gross primary productivity (GPP) and evaluated the spatiotemporal variations in seasonal GPP in response to climatic and soil water conditions from 1982 to 2018. Root-zone soil moisture consistently exerted a predominant positive influence on dryland GPP across all seasons, while the effect of surface soil moisture was less influential. Maximum temperature (Tmax) ranked as the second most influential factor on GPP, switching from a notable positive effect during cooler seasons to a negative impact during warmer seasons. Similarly, during cool seasons, vapor pressure deficit exhibited a notable positive effect on GPP, but this influence became negative in warmer seasons. Tmax indirectly regulated GPP by modulating the influence of other meteorological factors. During the warm season, Tmax negatively affected GPP via VPD, while in the cold season, it positively affected GPP through VPD. This study explicitly identifies the pivotal role of root-zone soil moisture in determining GPP and highlights the substantial seasonal differences and regulatory role of temperature in how other environmental variables influence GPP. These findings provide a novel perspective for understanding the responses of dryland ecosystems to climate change.

Global and Planetary Change↗