- Environmental statistician with the US Environmental Protection Agency. Research on survey design and analysis for a... moreEnvironmental statistician with the US Environmental Protection Agency. Research on survey design and analysis for aquatic resources. Participate in the National Aquatic Resource Surveys conducted by US EPAedit
ABSTRACT doi: 10.1899/11-075.1
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Forest health monitoring (FHM) focuses on the health of the forest ecosystem. Recognition of the importance of forest health and, especially, the role of monitoring, increased with the acceptance of the Santiago Declaration. The... more
Forest health monitoring (FHM) focuses on the health of the forest ecosystem. Recognition of the importance of forest health and, especially, the role of monitoring, increased with the acceptance of the Santiago Declaration. The declaration was accompanied by a set of criteria and indicators for the conservation and sustainable management of temperate and boreal forests. The criteria focus on conservation of biological diversity, maintenance of productive capacity, maintenance of forest ecosystem health, conservation of soil and water resources within forests, maintenance of forest contribution to global carbon cycles, and enhancement of long-term multiple socio-economic benefits to meet the needs of societies. The declaration calls for quantitative measurements of indicators associated with the criteria. The periodic and systematic measurement of the indicators requires nations to have FHM programs.
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ABSTRACT Land-management agencies need quantitative, statistically rigorous monitoring data, often at large spatial and temporal scales, to support resource-management decisions. Monitoring designs typically must accommodate multiple... more
ABSTRACT Land-management agencies need quantitative, statistically rigorous monitoring data, often at large spatial and temporal scales, to support resource-management decisions. Monitoring designs typically must accommodate multiple ecological, logistical, political, and economic objectives and constraints. We present a long-term bioregional monitoring program to assess the status and change in populations of the federally listed candidate frog species, Yosemite toad (Anaxyrus [Bufo] canorus) and mountain yellow-legged frog (Rana muscosa/sierrae complex), on USDA Forest Service lands in the Sierra Nevada, California. The program takes advantage of advances in survey design and analysis to: 1) collect data at a metapopulation scale (i.e., small basins), 2) provide occupancy data on ≥2 species with overlapping ranges with the same field-monitoring protocols, 3) provide occupancy estimates applicable to the entire range of each species in the study region, 4) incorporate information from historical occupancy records, and 5) link the survey design to an existing survey design. We estimated occupancy assuming imperfect detection by extending existing procedures for maximum likelihood estimation to incorporate the unequal probability of selection used in the survey design. From 2002 to 2009, we estimate that the Yosemite toad used 0.25 ± 0.01 (SE), 0.86 ± 0.04, and 0.86 ± 0.03 of basins over its range, with historical presence, and with presence since 1990, respectively, and the mountain yellow-legged frog used 0.04 ± 0.01, 0.43 ± 0.04, and 0.47 ± 0.04 of basins over its range, with historical presence, and with presence since 1990, respectively. Survey date and snow pack affected detection of the Yosemite toad but not of the mountain yellow-legged frog. Monitoring costs were reduced by using a complex survey design with panels that required generalizing existing methods for estimating occupancy under imperfect detection.
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Research Interests: Mathematics, Computer Science, Econometrics, Statistics, Environmental Pollution, and 15 moreGlobal Warming, Sampling methods, Environmental Issues, Sampling design, United States, Monitoring, Key words, Survey design, Sample Survey, Systematic, Natural Resource, Sampling Technique, Large Scale, Basal Area, and Sample space
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ABSTRACT This report summarizes the results of a much larger document that discusses methods to monitor wet, dry, and droplet deposition in the United States and Canada and provides temporal and spatial analyses. The introduction here... more
ABSTRACT This report summarizes the results of a much larger document that discusses methods to monitor wet, dry, and droplet deposition in the United States and Canada and provides temporal and spatial analyses. The introduction here gives the scope of the larger document, while the body of this report summarizes the important findings of wet, dry, and droplet deposition of the larger document. The main purpose of the larger document is to identify the locations of maximum deposition of pollutants and to determine if the spatial and temporal patterns have changed substantially during the period 1979 to 1987. A significant portion of the document addresses the representativeness and completeness of large-scale network deposition data at regional and local scales. 23 refs., 2 figs., 2 tabs.
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Research Interests: Zoology, Environmental Science, Time Series, Fisheries, Ecology, and 15 moreSampling design, Fishery Management, Population Size, Fisheries Sciences, Sample Size, Travel Time, Sampling strategy, Standard Error, Indexation, Simple Random Sampling, Chinook Salmon, Cluster Sampling, Confidence Interval, Oncorhynchus, and Stratified sampling
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Research Interests: Environmental Science, Chemistry, Bioaccumulation, Environmental Monitoring, Medicine, and 15 moreHumans, Mercury, Animals, Fishes, Human health, Great Salt Lake, Environmental monitoring and assessment, Adult, Fresh water, Contaminants, Developing nations, Lac, Environmental Exposure, Cumulant, and contaminant
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Annual 1979 and 1980 sulfate deposition data for 21 NADP monitoring stations with at least 20 weekly samples and with samples from each quarter are used to investigate the magnitude of change that is detectable in a statistical sense with... more
Annual 1979 and 1980 sulfate deposition data for 21 NADP monitoring stations with at least 20 weekly samples and with samples from each quarter are used to investigate the magnitude of change that is detectable in a statistical sense with high confidence. A statistical technique called Kriging is applied to obtain block area estimates and standard errors for average sulfate deposition. The block area covers most of New York, Connecticut, Rhode Island, Pennsylvania, West Virginia and Ohio. The estimates obtained are 35.0 kg/ha (3.5 g/m/sup 2/) and 31.8 kg/ha (3.2 g/m/sup 2/) for 1979 and 1980, respectively. The associated standard errors are 2.1 kg/ha (0.2 g/m/sup 2/) for both 1979 and 1980. Estimates of the minimum magnitude of annual sulfate deposition change detectable with 90% confidence are 8.8, 5.1 and 3.9 kg/ha (0.88, 0.51 and 0.39 g/m/sup 2/) when one, three and five years, respectively, of annual data are available before and after an intervention occurs. These estimates are based on optimum conditions and may be lower than minimum change detectable in practice. For example, the presence of trends or cycles in annual deposition would increase the minimum change detectable. An increase in the number of monitoring stations will providemore » additional information but not directly proportional to the increase. A preliminary estimate of the effect of doubling the number of monitoring stations is that the minimum detectable limit is 60% of the previous estimates. For one year before and after this reduces the value to 5.3 kg/ha compared to 8.8 kg/ha. 1 figure, 3 tables.« less
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The Acid Deposition System (ADS) for statistical reporting of acid precipitation data has been established by the US Environmental Protection Agency. The ADS data base system provides an integrated centralized data bank for atmospheric... more
The Acid Deposition System (ADS) for statistical reporting of acid precipitation data has been established by the US Environmental Protection Agency. The ADS data base system provides an integrated centralized data bank for atmospheric deposition data collected by all monitoring networks in North America. An overview of ADS is given. The underlying structure of the system is described, especially as it impacts potential uses of wet deposition data. North American monitoring networks currently participating in ADS are identified and the geographical coverage of sites are shown. Examples of standard statistical summaries available from ADS are given. Isopleth maps for pH, annual deposition of hydrogen, sulfate, nitrate and ammonium ion species for the period July 1980 to June 1981 are used to illustrate spatial analyses utilizing ADS. Spatial analysis is based on a statistical surface estimation procedure called kriging with the resulting surface then contoured. 20 references, 6 figures, 2 tables.
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Research Interests: Computer Science, Algorithms, Research Design, Environmental Management, Natural Resource Management, and 15 moreInference, Medicine, Multidisciplinary, Probability, Statistical Inference, Computer Simulation, Sampling design, Natural Resource, Conservation of Natural Resources, Long Term Monitoring, Field Data, Environmental, Geographic Information System, Geographic Information Systems, and Lot Quality Assurance Sampling
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Research Interests: Environmental Science, Environmental Monitoring, Medicine, Multidisciplinary, Population, and 15 moreHumans, Reservoir, Sampling design, Animals, Fishes, Surface Water, Data Collection, Reservoirs, Environmental monitoring and assessment, Fresh water, Contaminants, Lac, Environmental Protection Agency, Environmental Exposure, and contaminant
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This article presents three variations on boxplots for use in a spatial context. The three variations are linked mi-cromap boxplots, linked micromap bivariate boxplots, and angular boxplot glyphs. The specific examples
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A geodatabase of 387,237 points statistically chosen from the February 2005 version of the Washington DNR Hydrography layer representing stream site locations. For details, see the Design Documentation created by 3/18/2006 by Tony Olsen... more
A geodatabase of 387,237 points statistically chosen from the February 2005 version of the Washington DNR Hydrography layer representing stream site locations. For details, see the Design Documentation created by 3/18/2006 by Tony Olsen (U.S. EPA) and Janelle Black (NW Indian Fisheries Commission). The design document is available from the Washington State Department of Ecology at https://fortress.wa.gov/ecy/gispublic/DataDownload/documents/EPA_ENV_MasterSampleDesign.pdf.
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U.S. EPA conducted a national statistical survey of fish tissue contamination at 540 river sites (representing 82 954 river km) in 2008-2009, and analyzed samples for 50 persistent organic pollutants (POPs), including 21 PCB congeners, 8... more
U.S. EPA conducted a national statistical survey of fish tissue contamination at 540 river sites (representing 82 954 river km) in 2008-2009, and analyzed samples for 50 persistent organic pollutants (POPs), including 21 PCB congeners, 8 PBDE congeners, and 21 organochlorine pesticides. The survey results were used to provide national estimates of contamination for these POPs. PCBs were the most abundant, being measured in 93.5% of samples. Summed concentrations of the 21 PCB congeners had a national weighted mean of 32.7 μg/kg and a maximum concentration of 857 μg/kg, and exceeded the human health cancer screening value of 12 μg/kg in 48% of the national sampled population of river km, and in 70% of the urban sampled population. PBDEs (92.0%), chlordane (88.5%) and DDT (98.7%) were also detected frequently, although at lower concentrations. Results were examined by subpopulations of rivers, including urban or nonurban and three defined ecoregions. PCBs, PBDEs, and DDT occur at sign...
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???welcome.guest??? Sign In | Register. Search within: This issue. Advanced Search. Volume 27, Issue 4 (December 2008). ...
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In both examples the models used did not include terms for longitudinal and spatial effects because it was strongly felt that there was no prior knowledge of the interaction between the longitudinal/spatial structure and the design... more
In both examples the models used did not include terms for longitudinal and spatial effects because it was strongly felt that there was no prior knowledge of the interaction between the longitudinal/spatial structure and the design factors. By allowing the effects to freely vary over the fiber and over the wafer surface we guarded against most types of misspecification; yet the graphics we used to display the effects and coefficients effectively reveal their longitudinal and spatial dependence.
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This paper discusses the extent of virtual reality technology and raises an example of using a highly immersive environment for exploring and mining multivariate spatial data. The environment used for analysis is a 4 wall projection... more
This paper discusses the extent of virtual reality technology and raises an example of using a highly immersive environment for exploring and mining multivariate spatial data. The environment used for analysis is a 4 wall projection system called the C2 at Iowa State University. We look at water chemistry measurements made on a probability sample of wadeable streams in the mid-Atlantic states of the USA.
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Watershed integrity is the capacity of a watershed to support and maintain the full range of ecological processes and functions essential to sustainability. Using information from EPA's StreamCat dataset, we calculated and mapped an... more
Watershed integrity is the capacity of a watershed to support and maintain the full range of ecological processes and functions essential to sustainability. Using information from EPA's StreamCat dataset, we calculated and mapped an Index of Watershed Integrity (IWI) for 2.6 million watersheds in the conterminous US with first-order approximations of relationships between stressors and six watershed functions: hydrologic regulation, regulation of water chemistry, sediment regulation, hydrologic connectivity, temperature regulation, and habitat provision. Results show high integrity in the western US, intermediate integrity in the southern and eastern US, and the lowest integrity in the temperate plains and lower Mississippi Valley. Correlation between the six functional components was high ( = 0.85-0.98). A related Index of Catchment Integrity (ICI) was developed using local drainages of individual stream segments (i.e., excluding upstream information). We evaluated the ability ...
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Statistical models supporting inferences about species occurrence patterns in relation to environmental gradients are fundamental to ecology and conservation biology. A common implicit assumption is that the sampling design is ignorable... more
Statistical models supporting inferences about species occurrence patterns in relation to environmental gradients are fundamental to ecology and conservation biology. A common implicit assumption is that the sampling design is ignorable and does not need to be formally accounted for in analyses. The analyst assumes data are representative of the desired population and statistical modeling proceeds. However, if datasets from probability and non-probability surveys are combined or unequal selection probabilities are used, the design may be non ignorable. We outline the use of pseudo-maximum likelihood estimation for site-occupancy models to account for such non-ignorable survey designs. This estimation method accounts for the survey design by properly weighting the pseudo-likelihood equation. In our empirical example, legacy and newer randomly selected locations were surveyed for bats to bridge a historic statewide effort with an ongoing nationwide program. We provide a worked example...
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Random forest (RF) modeling has emerged as an important statistical learning method in ecology due to its exceptional predictive performance. However, for large and complex ecological data sets, there is limited guidance on variable... more
Random forest (RF) modeling has emerged as an important statistical learning method in ecology due to its exceptional predictive performance. However, for large and complex ecological data sets, there is limited guidance on variable selection methods for RF modeling. Typically, either a preselected set of predictor variables are used or stepwise procedures are employed which iteratively remove variables according to their importance measures. This paper investigates the application of variable selection methods to RF models for predicting probable biological stream condition. Our motivating data set consists of the good/poor condition of n = 1365 stream survey sites from the 2008/2009 National Rivers and Stream Assessment, and a large set (p = 212) of landscape features from the StreamCat data set as potential predictors. We compare two types of RF models: a full variable set model with all 212 predictors and a reduced variable set model selected using a backward elimination approac...
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Understanding and mapping the spatial variation in stream biological condition could provide an important tool for conservation, assessment, and restoration of stream ecosystems. The USEPA's 2008-2009 National... more
Understanding and mapping the spatial variation in stream biological condition could provide an important tool for conservation, assessment, and restoration of stream ecosystems. The USEPA's 2008-2009 National Rivers and Streams Assessment (NRSA) summarizes the percent of stream lengths within the conterminous US that are in good, fair, or poor biological condition based on a multimetric index of benthic invertebrate assemblages. However, condition is usually summarized at regional or national scales, and these assessments do not provide substantial insight into the spatial distribution of conditions at unsampled locations. We used random forests to model and predict the probable condition of several million kilometers of streams across the conterminous US based on nearby and upstream landscape features, including human-related alterations to watersheds. To do so, we linked NRSA sample sites to the USEPA's StreamCat Dataset; a database of several hundred landscape metrics for all 1:100,000-scale streams and their associated watersheds within the conterminous US. The StreamCat data provided geospatial indicators of nearby and upstream land use, land cover, climate, and other landscape features for modeling. Nationally, the model correctly predicted the biological condition class of 75% of NRSA sites. Although model evaluations suggested good discrimination among condition classes, we present maps as predicted probabilities of good condition, given upstream and nearby landscape settings. Inversely, the maps can be interpreted as the probability of a stream being in poor condition, given human-related watershed alterations. These predictions are available for download from the USEPA's StreamCat website (https://w w w .epa. gov/national-aquatic-resource-surveys/streamcat). Finally, we illustrate how these predictions could be used to prioritize streams for conservation or restoration. This article is protected by copyright. All rights reserved.
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We developed an extensive database of landscape metrics for ~2.65 million stream segments, and their associated catchments, within the conterminous United States (U.S.): The Stream-Catchment (StreamCat) Dataset. These data are publically... more
We developed an extensive database of landscape metrics for ~2.65 million stream segments, and their associated catchments, within the conterminous United States (U.S.): The Stream-Catchment (StreamCat) Dataset. These data are publically available (http://www2.epa.gov/national-aquatic-resource-surveys/streamcat) and greatly reduce the specialized geospatial expertise needed by researchers and managers to acquire landscape information for both catchments (i.e., the nearby landscape flowing directly into streams) and full upstream watersheds of specific stream reaches. When combined with an existing geospatial framework of the Nation's rivers and streams (National Hydrography Dataset Plus Version 2), the distribution of catchment and watershed characteristics can be visualized for the conterminous U.S. In this article, we document the development and main features of this dataset, including the suite of landscape features that were used to develop the data, scripts and algorithms used to accumulate and produce watershed summaries of landscape features, and the quality assurance procedures used to ensure data consistency. The StreamCat Dataset provides an important tool for stream researchers and managers to understand and characterize the Nation's rivers and streams.
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Description: This report describes the logic and design of an effectiveness monitoring program for the Northwest Forest Plan. The program is prospective, providing an early warning of environmental change before irreversible loss has... more
Description: This report describes the logic and design of an effectiveness monitoring program for the Northwest Forest Plan. The program is prospective, providing an early warning of environmental change before irreversible loss has occurred. Monitoring is focused at two resource ...
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Natural and human-related landscape features influence the ecology and water quality of lakes. Summarizing these features in a hydrologically meaningful way is critical to understanding and managing lake ecosystems. Such summaries are... more
Natural and human-related landscape features influence the ecology and water quality of lakes. Summarizing these features in a hydrologically meaningful way is critical to understanding and managing lake ecosystems. Such summaries are often done by delineating watershed boundaries of individual lakes. However, many technical challenges are associated with delineating hundreds or thousands of lake watersheds at broad spatial extents. These challenges can limit the application of analyses and models to new, unsampled locations. We present the Lake-Catchment (LakeCat) Dataset (https://www.epa.gov/national-aquatic-resource-surveys/lakecat) of watershed features for 378,088 lakes within the conterminous USA. We describe the methods we used to: 1) delineate lake catchments, 2) hydrologically connect nested lake catchments, and 3) generate several hundred watershed-level metrics that summarize both natural (e.g., soils, geology, climate, and land cover) and anthropogenic (e.g., urbanizatio...
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ABSTRACT Elevated mercury concentrations in fish are the leading cause of fish consumption advisories. In a continuing effort to characterize the extent of mercury contamination in U.S. waters, EPA’s Office of Water and Office of Research... more
ABSTRACT Elevated mercury concentrations in fish are the leading cause of fish consumption advisories. In a continuing effort to characterize the extent of mercury contamination in U.S. waters, EPA’s Office of Water and Office of Research and Development collaborated to conduct the first statistically-based survey of mercury in fish from U.S. rivers (under the framework of the National Rivers and Streams Assessment). Fish were collected at 542 randomly selected river sites (≥ 5th order) in the lower 48 states during 2008 and 2009. One composite sample of five similarly sized adult fish of the same species was collected at each site, focusing on fishes commonly consumed by humans. Largemouth bass Micropterus salmoides and smallmouth bass M. dolomieu accounted for 34% and 24% of all composites, respectively. Fillets were analyzed for total mercury using a Direct Mercury Analyzer. Mercury was detected at quantifiable levels in all samples. Based on this probabilistic study, the mean and maximum concentrations of mercury in fish fillets from U.S. rivers were 229 ppb and 1,419 ppb, respectively. Probability-based results showed that 25.3% (or 13,071 river miles) of the total 51,663 river miles included in this survey had mercury fish tissue concentrations that exceeded EPA’s 300 ppb human health screening value.