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At least 1,297 records · Page 72Linked to original sources
USGS2006

Dealing with uncertainty and sensitivity issues in process-based models of carbon and nitrogen cycles in northern forest ecosystems

Many process-based models on carbon (C) and nitrogen (N) cycles have been developed for northern forest ecosystems. These models are widely used to evaluate the long-term decisions in forest management dealing with effects like particulate pollution, productivity and climate change. Regarding climate change, one of the key questions that have sensitive political implications is whether northern forests will sequester atmospheric C or not. Whilst many process-based models have been tested for accuracy by evaluating or validating against observed data, few have dealt with the complexity of the incorporated procedures to estimate uncertainties associated with model predictions or the sensitivity of these predictions to input factors in a systematic, inter-model comparison fashion. In general, models differ in their underlying attempts to match natural complexities with assumed or imposed model structure and process formulations to estimate model parameters, to gather data and to address issues on scope, scale and natural variations. Uncertainties may originate from model structure, estimation of model parameters, data input, representation of natural variation and scaling exercises. Model structure relates to the mathematical representation of the processes modelled and the type of state variables that a model contains. The modelling of partitioning among above- and below-ground C and N pools and the interdependence among these pools remain a major source of uncertainty in model structure and error propagation. Most soil C models use at least three state variables to represent the different types of soil organic matter (SOM). This approach results in creating three artificial SOM pools, assuming that each one contains C compounds with same turnover rate. In reality, SOM consists of many different types of C compounds with widely different turnover rates. Uncertainty in data and parameter estimates are closely linked. Data uncertainties are associated with high variations in estimating forest biomass, productivity and soil organic matter and may be incomplete for model initialization, calibration, validation and sensitivity analysis of generalized predictor models. The scale at which a model is being used also affects the level of uncertainty, as the errors in the prediction of the C and N dynamics differ from the site to the landscape levels and across climatic regions. If the spatial or temporal scale of a model application is changed, additional uncertainty arises from neglecting natural variability in system variables in time and space. Uncertainty issues are also intimately related to model validation and sensitivity analysis. The estimation of uncertainties is needed to inform decision process, in order to detect the possible corridor of development. Uncertainty in this context is an essential measure of quality for stakeholder and decision makers.

Conference Paper↗
USGS2025

A review of abrupt permafrost thaw: Definitions, usage, and a proposed conceptual framework

Purpose of Review We review how ‘abrupt thaw’ has been used in published studies, compare these definitions to abrupt processes in other Earth science disciplines, and provide a definitive framework for how abrupt thaw should be used in the context of permafrost science. Recent Findings We address several aspects of permafrost systems necessary for abrupt thaw to occur and propose a framework for classifying permafrost processes as abrupt thaw in the future. Based on a literature review and our collective expertise, we propose that abrupt thaw refers to thaw processes that lead to a substantial persistent environmental change within a few decades. Abrupt thaw typically occurs in ice-rich permafrost but may be initiated in ice-poor permafrost by external factors such as hydrologic change (i.e., increased streamflow, soil moisture fluctuations, altered groundwater recharge) or wildfire. Summary Permafrost thaw alters greenhouse gas emissions, soil and vegetation properties, and hydrologic flow, threatening infrastructure and the cultures and livelihoods of northern communities. The term ‘abrupt thaw’ has emerged in scientific discourse over the past two decades to differentiate processes that rapidly impact large depths of permafrost, such as thermokarst, from more gradual, top-down thaw processes that impact centimeters of near-surface permafrost over years to decades. However, there has been no formal definition for abrupt thaw and its use in the scientific literature has varied considerably. Our standardized definition of abrupt thaw offers a path forward to better understand drivers and patterns of abrupt thaw and its consequences for global greenhouse gas budgets, impacts to infrastructure and land-use, and Arctic policy- and decision-making.

Current Climate Change Reports↗
USGS2012

Modeling of land use and reservoir effects on nonpoint source pollution in a highly agricultural basin

Nonpoint source (NPS) pollution is tightly linked to land use activities that determine the sources and magnitudes of pollutant loadings to stream water. The pollutant loads may also be alleviated within reservoirs because of the physical interception resulting from changed hydrological regimes and other biochemical processes. It is important but challenging to assess the NPS pollution processes with human effects due to the measurement limitations. The objective of this study is to evaluate the effects of human activities such as land uses and reservoir operation on the hydrological and NPS pollution processes in a highly agricultural area-the Iowa River Basin-using the Soil and Water Assessment Tool (SWAT). The evaluation of model performance at multiple sites reveals that SWAT can consistently simulate the daily streamflow, and monthly/annual sediment and nutrient loads (nitrate nitrogen and mineral phosphorus) in the basin. We also used the calibrated model to estimate the trap efficiencies of sediment (~78%) and nutrients (~30%) in the Coralville Reservoir within the basin. These non-negligible effects emphasize the significance of incorporating the sediment and nutrient removal mechanisms into watershed system studies. The spatial quantification of the critical NPS pollution loads can help identify hot-spot areas that are likely locations for the best management practices.

Iowa↗
USGS2000

Occurrence of organochlorine pesticides in streambed sediment and fish from selected streams on the island of Oahu, Hawaii, 1998

Organochlorine pesticides were heavily used from the mid-1940s to the mid-1980s. The persistence of organochlorine pesticides, their tendency to accumulate in soil, sediment, and biota, and their harmful effects on wildlife brought this class of compounds into disfavor and eventually resulted in restriction or cancellation of most of them in the United States (Nowell and others, 1999). Despite use restrictions, these compounds continue to be detected in sediment and fish tissue samples. This study was undertaken as part of the National Water-Quality Assessment (NAWQA) program of the U.S. Geological Survey (USGS). The NAWQA program assesses watersheds as integrated systems, focusing on chemical concentrations, physical conditions, and biological status in streams. One component of NAWQA is an occurrence survey of organic contaminants and trace elements in stream bed sediment and fish tissue. The goal of the Oahu stream bed sediment and fish tissue occurrence survey was to determine which organochlorine contaminants are present in streams around the island, and with which land uses they are associated. An understanding of relations between land use and organochlorine compounds will allow land management practices to be designed to reduce the loading of contaminants to streams and nearshore waters.

Hawaii↗
USGS2004

Estimated water use in Arkansas, 2000

The water-use program in Arkansas is a cooperative effort between Arkansas Soil and Water Conservation Commission and the U.S. Geological Survey. During 2000, the amount of water withdrawn from ground- and surface-water sources in Arkansas was estimated to be 10,963 million gallons per day (Mgalld). Of this amount, about 6,952 Mgal/d (63 percent) were from ground water and about 4,011 Mgalld (37 percent) were from surface-water sources. Approximately 87 percent of the population (2.3 million people) in Arkansas were served by public supply systems during 2000. These systems withdrew approximately 427 Mgal/d. Most of the water, 69 percent, was from surface-water sources. The statewide average for per-capita residential use from public supply systems was 181 gallons per day and increased about 57 percent between 1965 and 2000.

Arkansas↗
USGS2003

Arctic transitions in the Land - Atmosphere System (ATLAS): Background, objectives, results, and future directions

This paper briefly reviews the background, objectives, and results of the Arctic Transitions in the Land-Atmosphere System (ATLAS) Project to date and provides thoughts on future directions. The key goal of the ATLAS Project is to improve understanding of controls over spatial and temporal variability of terrestrial processes in the Arctic that have potential consequences for the climate system, i.e., processes that affect the exchange of water and energy with the atmosphere, the exchange of radiatively active gases with the atmosphere, and the delivery of freshwater to the Arctic Ocean. Three important conclusions have emerged from research associated with the ATLAS Project. First, associated with the observation that the Alaskan Arctic has warmed significantly in the last 30 years, permafrost is warming, shrubs are expanding, and there has been a temporary release of carbon dioxide from tundra soils. Second, the winter is a more important period of biological activity than previously appreciated. Biotic processes, including shrub expansion and decomposition, affect snow structure and accumulation and affect the annual carbon budget of tundra ecosystems. Third, observed vegetation changes can have a significant positive feedback to regional warming. These vegetation effects are, however, less strong than those exerted by land-ocean heating contrasts and the topographic constraints on air mass movements. The papers of this special section provide additional insights related to these conclusions and to the overall goal of ATLAS.

Journal of Geophysical Research D: Atmospheres↗
USGS1982

Mitigation and enhancement techniques for the Upper Mississippi River system and other large river systems

Extensive information is provided on techniques that can reduce or eliminate the negative impact of man's activities (particularly those related to navigation) on large river systems, with special reference to the Upper Mississippi River. These techniques should help resource managers who are concerned with such river systems to establish sound environmental programs. Discussion of each technique or group of techniques include (1) situation to be mitigated or enhanced; (2) description of technique; (3) impacts on the environment; (4) costs; and (5) evaluation for use on the Upper Mississippi River Systems. The techniques are divided into four primary categories: Bank Stabilization Techniques, Dredging and Disposal of Dredged Material, Fishery Management Techniques, and Wildlife Management Techniques. Because techniques have been grouped by function, rather than by structure, some structures are discussed in several contexts. For example, gabions are discussed for use in revetments, river training structures, and breakwaters. The measures covered under Bank Stabilization Techniques include the use of riprap revetments, other revetments, bulkheads, river training structures, breakwater structures, chemical soil stabilizers, erosion-control mattings, and filter fabrics; the planting of vegetation; the creation of islands; the creation of berms or enrichment of beaches; and the control of water level and boat traffic. The discussions of Dredging and the Disposal of Dredged Material consider dredges, dredging methods, and disposal of dredged material. The following subjects are considered under Fishery Management Techniques: fish attractors; spawning structures; nursery ponds, coves, and marshes; fish screens and barriers; fish passage; water control structures; management of water levels and flows; wing dam modification; side channel modification; aeration techniques; control of nuisance aquatic plants; and manipulated of fish populations. Wildlife Management Techniques include treatments of artificial nest structures, island creation or development, marsh creation or development, greentree reservoirs and mast management, vegetation control, water level control, and revegetation.

Upper Mississippi River↗
USGS2014

Data worth and prediction uncertainty for pesticide transport and fate models in Nebraska and Maryland, United States

BACKGROUND Complex environmental models are frequently extrapolated to overcome data limitations in space and time, but quantifying data worth to such models is rarely attempted. The authors determined which field observations most informed the parameters of agricultural system models applied to field sites in Nebraska (NE) and Maryland (MD), and identified parameters and observations that most influenced prediction uncertainty. RESULTS The standard error of regression of the calibrated models was about the same at both NE (0.59) and MD (0.58), and overall reductions in prediction uncertainties of metolachlor and metolachlor ethane sulfonic acid concentrations were 98.0 and 98.6% respectively. Observation data groups reduced the prediction uncertainty by 55–90% at NE and by 28–96% at MD. Soil hydraulic parameters were well informed by the observed data at both sites, but pesticide and macropore properties had comparatively larger contributions after model calibration. CONCLUSIONS Although the observed data were sparse, they substantially reduced prediction uncertainty in unsampled regions of pesticide breakthrough curves. Nitrate evidently functioned as a surrogate for soil hydraulic data in well-drained loam soils conducive to conservative transport of nitrogen. Pesticide properties and macropore parameters could most benefit from improved characterization further to reduce model misfit and prediction uncertainty. RESULTS: The standard error of regression of the calibrated models was about the same at both NE (0.59) and MD (0.58), and overall reductions in prediction uncertainties of metolachlor and metolachlor ethane sulfonic acid concentrations were 98.0 and 98.6% respectively. Observation data groups reduced the prediction uncertainty by 55–90% at NE and by 28–96% at MD. Soil hydraulic parameters were well informed by the observed data at both sites, but pesticide and macropore properties had comparatively larger contributions after model calibration. CONCLUSIONS: Although the observed data were sparse, they substantially reduced prediction uncertainty in unsampled regions of pesticide breakthrough curves. Nitrate evidently functioned as a surrogate for soil hydraulic data in well-drained loam soils conducive to conservative transport of nitrogen. Pesticide properties and macropore parameters could most benefit from improved characterization further to reduce model misfit and prediction uncertainty.

Maryl;Nebraska↗
USGS2021

Remote sensing-based actual evapotranspiration assessment in a data-scarce area of Brazil: A case study of the Urucuia Aquifer System

The large groundwater reserves of the Urucuia Aquifer System (UAS) enabled agricultural development and economic growth in the western Bahia State, in northeastern Brazil. Over the last several years, concern has grown around the aquifer’s diminishing water levels, and water balance (WB) studies are in demand. Considering the lack of measured actual evapotranspiration (ET a ), a major component of the water cycle, this work uses the Operational Simplified Surface Energy Balance (SSEBop) model to estimate ET a , and compares it to basin-scale estimates from the Soil Moisture Accounting Procedure (SMAP) monthly model and from an annual WB closure method, based on gridded meteorological data and the Gravity Recovery and Climate Experiment (GRACE) product. Additionally, a comparative assessment of different versions of the SSEBop parameterization was performed. Moderate Resolution Imaging Spectroradiometer (MODIS) imagery was used to implement eight different versions of the SSEBop algorithm over the UAS between 2000 and 2013. SSEBop and SMAP ET a yielded similar seasonal patterns, with correlation coefficient (r) up to 0.65, mean difference (MD) of 0.8 mm/month and mean absolute difference (MAD) of 18.5 mm/month. Comparison of SSEBop annual ET a estimates to annual SMAP and WB closure estimates yielded low MD (12.1 and −7.3 mm/year, respectively) and MAD (82.5 and 82.8 mm/year, respectively), but also low r values (0.00 and 0.37, respectively). The comparison of the different SSEBop versions indicated the need to incorporate a calibration step of the aerodynamic heat resistance (r ah ) parameter. SSEBop results were also used for land cover and drought monitoring. Analysis indicates that agriculture, associated with an increasing trend of atmospheric evaporative demand, is responsible for the decrease in groundwater levels and streamflow in the studied time period.

Urucuia Aquifer System↗
USGS2009

Predicting the probability and volume of postwildfire debris flows in the intermountain western United States

Empirical models to estimate the probability of occurrence and volume of postwildfire debris flows can be quickly implemented in a geographic information system (GIS) to generate debris-flow hazard maps either before or immediately following wildfires. Models that can be used to calculate the probability of debris-flow production from individual drainage basins in response to a given storm were developed using logistic regression analyses of a database from 388 basins located in 15 burned areas located throughout the U.S. Intermountain West. The models describe debris-flow probability as a function of readily obtained measures of areal burned extent, soil properties, basin morphology, and rainfall from short-duration and low-recurrence-interval convective rainstorms. A model for estimating the volume of material that may issue from a basin mouth in response to a given storm was developed using multiple linear regression analysis of a database from 56 basins burned by eight fires. This model describes debris-flow volume as a function of the basin gradient, aerial burned extent, and storm rainfall. Applications of a probability model and the volume model for hazard assessments are illustrated using information from the 2003 Hot Creek fire in central Idaho. The predictive strength of the approach in this setting is evaluated using information on the response of this fire to a localized thunderstorm in August 2003. The mapping approach presented here identifies those basins that are most prone to the largest debris-flow events and thus provides information necessary to prioritize areas for postfire erosion mitigation, warnings, and prefire management efforts throughout the Intermountain West.

Geological Society of America Bulletin↗
USGS2007

Natural landscape and stream segment attributes influencing the distribution and relative abundance of riverine smallmouth bass in Missouri

Protecting and restoring fish populations on a regional basis are most effective if the multiscale factors responsible for the relative quality of a fishery are known. We spatially linked Missouri's statewide historical fish collections to environmental features in a geographic information system, which was used as a basis for modeling the importance of landscape and stream segment features in supporting a population of smallmouth bass Micropterus dolomieu. Decision tree analyses were used to develop probability-based models to predict statewide occurrence and within-range relative abundances. We were able to identify the range of smallmouth bass throughout Missouri and the probability of occurrence within that range by using a few broad landscape variables: the percentage of coarse-textured soils in the watershed, watershed relief, and the percentage of soils with low permeability in the watershed. The within-range relative abundance model included both landscape and stream segment variables. As with the statewide probability of occurrence model, soil permeability was particularly significant. The predicted relative abundance of smallmouth bass in stream segments containing low percentages of permeable soils was further influenced by channel gradient, stream size, spring-flow volume, and local slope. Assessment of model accuracy with an independent data set showed good concordance. A conceptual framework involving naturally occurring factors that affect smallmouth bass potential is presented as a comparative model for assessing transferability to other geographic areas and for studying potential land use and biotic effects. We also identify the benefits, caveats, and data requirements necessary to improve predictions and promote ecological understanding. ?? Copyright by the American Fisheries Society 2007.

North American Journal of Fisheries Management↗
USGS2011

Alaska Geochemical Database (AGDB)-Geochemical data for rock, sediment, soil, mineral, and concentrate sample media

The Alaska Geochemical Database (AGDB) was created and designed to compile and integrate geochemical data from Alaska in order to facilitate geologic mapping, petrologic studies, mineral resource assessments, definition of geochemical baseline values and statistics, environmental impact assessments, and studies in medical geology. This Microsoft Access database serves as a data archive in support of present and future Alaskan geologic and geochemical projects, and contains data tables describing historical and new quantitative and qualitative geochemical analyses. The analytical results were determined by 85 laboratory and field analytical methods on 264,095 rock, sediment, soil, mineral and heavy-mineral concentrate samples. Most samples were collected by U.S. Geological Survey (USGS) personnel and analyzed in USGS laboratories or, under contracts, in commercial analytical laboratories. These data represent analyses of samples collected as part of various USGS programs and projects from 1962 to 2009. In addition, mineralogical data from 18,138 nonmagnetic heavy mineral concentrate samples are included in this database. The AGDB includes historical geochemical data originally archived in the USGS Rock Analysis Storage System (RASS) database, used from the mid-1960s through the late 1980s and the USGS PLUTO database used from the mid-1970s through the mid-1990s. All of these data are currently maintained in the Oracle-based National Geochemical Database (NGDB). Retrievals from the NGDB were used to generate most of the AGDB data set. These data were checked for accuracy regarding sample location, sample media type, and analytical methods used. This arduous process of reviewing, verifying and, where necessary, editing all USGS geochemical data resulted in a significantly improved Alaska geochemical dataset. USGS data that were not previously in the NGDB because the data predate the earliest USGS geochemical databases, or were once excluded for programmatic reasons, are included here in the AGDB and will be added to the NGDB. The AGDB data provided here are the most accurate and complete to date, and should be useful for a wide variety of geochemical studies. The AGDB data provided in the linked database may be updated or changed periodically. The data on the DVD and in the data downloads provided with this report are current as of date of publication.

Data Series↗
USGS1984

Restoration of freshwater in the Cano Tiburones area, Puerto Rico

Cano Tiburones on the north coast of Puerto Rico originally was a shallow, coastal lagoon, 9 square miles in area. It accumulated freshwater from adjacent rivers and springs and drained to the ocean through unobserved subterranean conduits. Forced drainage by pumping of Cano Tiburones for agriculture was begun in 1949, and resulted in lowering the water level to below sea level. The reversed hydraulic gradient permitted seawater to enter the Cano through the conduits forming seawater "springs". Seawater flooding caused widespread sodium chloride contamination in the canals and laterals and in the soils. Agricultural expectations of the area were not realized. The present investigation into the freshening potential of Cano Tiburones (1979-1982) determined that ground-water discharge does not contribute to salty conditions. On-site experiments were performed to segregate freshwater from seawater using differences in hydraulic head. Dams were constructed on canals and laterals, forcing accumulated saltwater to the ocean. Ring levees were placed around the discharging seawater conduits until sea level was reached and flow to the system stopped. These efforts have succeeded in reducing the amount of seawater in Cano Tiburones to one-third of its original concentration. Most of the water presently in Cano Tiburones is suitable for irrigation.

Cano Tiburones↗
USGS2011

Hydrologic and geomorphic considerations in restoration of river-floodplain connectivity in a highly altered river system, Lower Missouri River, USA

Planning for restoration of river-floodplain systems requires understanding how often and how much of a floodplain may be inundated, and how likely the floodplain is to retain the water once flooded. These factors depend fundamentally on hydrology and geomorphology of the channel and floodplain. We discuss application of an index of river-floodplain connectivity, the Land Capability Potential Index (LCPI), to regional-scale restoration planning along 600 km of the Lower Missouri River. The LCPI integrates modeled water-surface elevations, floodplain topography, and soils to index relative wetness of floodplain patches. Geomorphic adjustment of the Lower Missouri River to impoundment and channel engineering has altered the natural relations among hydrology, geomorphology, and floodplain soils, and has resulted in a regional upstream to downstream gradient in connectivity potential. As a result, flow-regime management is limited in its capacity to restore floodplain ecosystems. The LCPI provides a tool for identifying and mapping floodplain restoration potential, accounting for the geomorphic adjustment. Using simple criteria, we illustrate the utility of LCPI-like approaches in regional planning for restoration of plains cottonwood ( Populus deltoides ) communities, hydrologically connected floodplain wetlands, and seasonal floodplain wetlands.

Lower Missouri River↗
USGS2010

Use of regression‐based models to map sensitivity of aquatic resources to atmospheric deposition in Yosemite National Park, USA

An abundance of exposed bedrock, sparse soil and vegetation, and fast hydrologic flushing rates make aquatic ecosystems in Yosemite National Park susceptible to nutrient enrichment and episodic acidification due to atmospheric deposition of nitrogen (N) and sulfur (S). In this study, multiple linear regression (MLR) models were created to estimate fall‐season nitrate and acid neutralizing capacity (ANC) in surface water in Yosemite wilderness. Input data included estimated winter N deposition, fall‐season surface‐water chemistry measurements at 52 sites, and basin characteristics derived from geographic information system layers of topography, geology, and vegetation. The MLR models accounted for 84% and 70% of the variance in surface‐water nitrate and ANC, respectively. Explanatory variables (and the sign of their coefficients) for nitrate included elevation (positive) and the abundance of neoglacial and talus deposits (positive), unvegetated terrain (positive), alluvium (negative), and riparian (negative) areas in the basins. Explanatory variables for ANC included basin area (positive) and the abundance of metamorphic rocks (positive), unvegetated terrain (negative), water (negative), and winter N deposition (negative) in the basins. The MLR equations were applied to 1407 stream reaches delineated in the National Hydrography Data Set for Yosemite, and maps of predicted surface‐water nitrate and ANC concentrations were created. Predicted surface‐water nitrate concentrations were highest in small, high‐elevation cirques, and concentrations declined downstream. Predicted ANC concentrations showed the opposite pattern, except in high‐elevation areas underlain by metamorphic rocks along the Sierran Crest, which had relatively high predicted ANC (>200 μ eq L −1 ). Maps were created to show where basin characteristics predispose aquatic resources to nutrient enrichment and acidification effects from N and S deposition. The maps can be used to help guide development of water‐quality programs designed to monitor and protect natural resources in national parks.

Yosemite Nataional Park↗
USGS1994

The relationship between species richness and community biomass: The importance of environmental variables

Several studies have used plant community biomass to predict species richness with varying success. In this study we examined the relationship between species richness and biomass for 36 marsh communities from two different watersheds. In addition, we measured several environmental variables and estimated the potential richness (the total number of species known to be able to occur in a community type) for each community. Above ground living and dead biomass combined was found to be weakly correlated with species richness (R 2 =0.02). Instead, a multiple regression model based on elevation (R 2 =0.47), salinity (R 2 =0.30), soil organic matter (R 2 =0.18), and biomass was able to explain 82% of the variance in species richness. It was found that environmental conditions could explain 89% of the variation in potential richness. Biomass had no relation to potential richness. When used as a predictor variable, potential richness was found to explain 72% of the variation in realized (observed) richness and biomass explained an addition 9% of the variance in realized richness. This finding suggests that realized richness in our system was controlled primarily by environmental regulation of potential richness and secondarily by biomass (as an indicator of competition). Further examination of the data revealed that when sites exposed to extreme environmental conditons were eliminated from the analysis, biomass became the primary predictor of realized richness and potential richness was of secondary importance. We conclude that community biomass has a limited capacity to predict species richness across a broad range of habitat conditions. Of particular importance is the inability of biomass to indicate the effect of environmental factors and evolutionary history on the potential species richness at a site.

Louisiana↗
USGS2013

Estimating ecosystem carbon stocks at Redwood National and State Parks

Accounting for ecosystem carbon is increasingly important for park managers. In this case study we present our efforts to estimate carbon stocks and the effects of management on carbon stocks for Redwood National and State Parks in northern California. Using currently available information, we estimate that on average these parks’ soils contain approximately 89 tons of carbon per acre (200 Mg C per ha), while vegetation contains about 130 tons C per acre (300 Mg C per ha). estoration activities at the parks (logging-road removal, second-growth forest management) were shown to initially reduce ecosystem carbon, but may provide for enhanced ecosystem carbon storage over the long term. We highlight currently available tools that could be used to estimate ecosystem carbon at other units of the National Park System.

California↗
USGS2012

The General Ensemble Biogeochemical Modeling System (GEMS) and its applications to agricultural systems in the United States: Chapter 18

The General Ensemble Biogeochemical Modeling System (GEMS) was es in individual models, it uses multiple site-scale biogeochemical models to perform model simulations. Second, it adopts Monte Carlo ensemble simulations of each simulation unit (one site/pixel or group of sites/pixels with similar biophysical conditions) to incorporate uncertainties and variability (as measured by variances and covariance) of input variables into model simulations. In this chapter, we illustrate the applications of GEMS at the site and regional scales with an emphasis on incorporating agricultural practices. Challenges in modeling soil carbon dynamics and greenhouse emissions are also discussed.

Book chapter↗