Grantee Research Project Results
2002 Progress Report: Hierarchical Physical Classification of Western Streams: Predicting Biological Condition in Terms of Key Environmental Processes Bridging Local to Ecoregional Scales
EPA Grant Number: R828636Title: Hierarchical Physical Classification of Western Streams: Predicting Biological Condition in Terms of Key Environmental Processes Bridging Local to Ecoregional Scales
Investigators: Bledsoe, Brian P. , Wohl, Ellen E. , Poff, N. LeRoy
Institution: Colorado State University
EPA Project Officer: Packard, Benjamin H
Project Period: January 15, 2001 through January 14, 2004 (Extended to January 14, 2005)
Project Period Covered by this Report: January 15, 2002 through January 14, 2003
Project Amount: $788,144
RFA: Development of National Aquatic Ecosystem Classifications and Reference Conditions (2000) RFA Text | Recipients Lists
Research Category: Water , Aquatic Ecosystems
Objective:
Existing physical classifications for streams do not explicitly include considerations of how primary environmental drivers such as flow regime, geophysical setting, intermediate-scale geomorphic processes, and anthropogenic impacts interact and vary in importance across spatial scales in controlling stream environments and shaping biotic communities. We are developing a hierarchical classification framework for stream environments in the Western United States that identifies the relative importance of key environmental constraints or "filters" operating across multiple spatial scales. This a priori classification integrates hydrologic regime, geologic context, and critical geomorphic processes with reach classification. Given the current emphasis on ecoregional and local scales in biomonitoring protocols, this approach will provide essential information on how environmental factors measured at intermediate scales (watershed, valley bottom/geomorphic process domain, and reach) can be used to understand and predict biotic condition at individual sites distributed across the landscape. Specific objectives of this research project are to: (1) develop an exhaustive, multiscaled physical habitat classification of Western United States' streams to derive predictive statistical models relating biotic condition to multiscaled environmental variables; (2) demonstrate the explanatory power and flexibility of the classification within and across diverse Western United States' ecoregions; (3) explicitly assess how well a classification that includes intermediate scale processes (at the valley bottom/process-domain scale) can predict biotic condition at localities without requiring extensive local (reach scale) habitat data; and (4) develop a systematic approach for objectively identifying and stratifying reference sites.
Progress Summary:
In Year 2 of the project, the a priori physical classification and the suite of metrics describing the physiochemical environment at multiple scales across OR, WA, and CO Regional Environmental Monitoring and Assessment Program and Environmental Monitoring and Assessment Program (EMAP) sites have been significantly refined. A manuscript describing the a priori hierarchical stream classification has been developed and will be submitted for publication in early 2003. We also are nearing completion of the comprehensive matrix of hydrogeomorphic descriptors at the watershed, process domain/valley, and reach scales and have now begun preliminary testing with biological data (both taxonomic and functional) to assess the explanatory power and robustness of the multiscale physical and chemical variables. The forthcoming analysis of biological data will represent the first time many of the metrics describing valley-scale characteristics and the morphometric/energy structure of the upstream drainage network have been used in explaining biological variation across landscapes.
Relationships among multiscale physical characteristics as well as key physical factors influencing benthic macroinvertebrate assemblages were explored for stream sites sampled in OR and CO in a preliminary regression analysis. Linkages between the scale of environmental descriptors (i.e., watershed vs. local) and the geographic extent of compared sites were examined in models predicting biological condition. A direct gradient statistical analysis technique was used to elucidate the best scale for analyzing variability in macroinvertebrate assemblages, using up to 4 metrics, across three geographic extents: between states, within a state, and within an ecoregion. In the Cascades Ecoregion of OR, up to 71 percent of the variation in macroinvertebrate richness at a site was explained using a total of four local and watershed-scale metrics. A relationship for sensitive species richness at sites throughout the state of OR also performed well (R2 = 0.59) with watershed-scale metrics such as physical basin descriptors and disturbance indicators driving the relationship. An evident trend in the results for sites distributed over a geographic range comparable to the Cascades Ecoregion is that local-scale metrics, such as bed substrate descriptors, are the strongest predictors of macroinvertebrate richness. In contrast, metrics at the watershed scale are the most robust when the geographic range increases to the entire state of OR. Across all geographic extents investigated in this study, the relationships developed to explain variability in macroinvertebrate communities as a function of local habitat and watershed condition generally contained land cover descriptors, watershed-scale disturbance measures, and an indicator of streambed substrate condition.
Associations between environmental variables at both spatial scales were explored to examine whether these variables are hierarchically related. The results to date consistently show stronger relationships metrics from multiple scales are combined to describe macroinvertebrate assemblages as opposed to using one scale independently, regardless of the geographic extent of the sampled sites. Additionally, the results illustrate the importance of accounting for overarching processes when comparing a group of sites. In CO, the strength of the relationship for sensitive species richness (R2 = 0.39) substantially increased when heavy-metal impacts associated with mining were accounted for (R2 = 0.53).
We have held another series of meetings with other Science to Achieve Results (STAR) grant recipients from Colorado State University (Space-Time Aquatic Resources Modeling and Analysis Program, Co-Project Investigators: JA Hoeting, NS Urquhart, DM Theobald) to enhance collaborations.
Future Activities:
Once the matrix of chemical and physical descriptors is finalized at all three spatial scales, we will employ several statistical analyses (multiple regression, Canonical Correlation Analysis, Canonical Discriminant Analysis, Stochastic CART analysis, and other approaches) to elucidate the key physical controls on biological communities and build the hierarchical classification. Estimates of ecologically relevant flow regime statistics at ungauged field sites will be combined with local habitat and substrate attributes in Year 3 to characterize site-specific disturbance regimes.
We will apply the classification in collaboration with the State of Montana to stratify diverse stream environments and systematically identify probable reference sites using multiscale physical and chemical information. We also will examine the predictive utility of the classification by comparing the ecological health of these reference sites versus sites selected using less systematic methods. This application will assist in further generalization of the classification, improving user friendliness, and demonstrating practical applications.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
| Other project views: | All 11 publications | 2 publications in selected types | All 2 journal articles |
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Olden JD, Poff NL. Redundancy and the choice of hydrologic indices for characterizing streamflow regimes. River Research and Applications 2003;19(2):101-121. |
R828636 (2002) |
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Poff NL, Hart DD. How dams vary and why it matters for the emerging science of dam removal. BioScience 2002;52(8):659-668. |
R828636 (2002) |
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Supplemental Keywords:
scaling, aquatic, indicators, EPA Region 8, EPA Region 9, EPA Region 10., RFA, Scientific Discipline, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Aquatic Ecosystems & Estuarine Research, Hydrology, State, Aquatic Ecosystem, Ecology and Ecosystems, Ecological Risk Assessment, biocriteria, EMAP, streams, Oregon, multiple spatial scales, ecoregional scale, Washington (WA), hierarchical physical classification, water quality, biological indicators, ecological classification, predicting biological condition, Colorado (CO)Relevant Websites:
http://www.engr.colostate.edu/~bbledsoe Exit
http://lamar.colostate.edu/~poff/home.html Exit
http://www.cnr.colostate.edu/ER/fac-staff/home/ellenw.html Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.