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USFS Classification of Columbia River Basin Riparian Vegetation

Project Type: Collaboration
Project Sponsor: USDA Forest Service PACFISH/INFISH Biological Opinion
Project Location: Washington, Oregon, Idaho, Montana, Utah and Nevada
Status: Ongoing

Project Overview

Purpose of Project

This project identifies relationships between riparian vegetation and environmental filters to elucidate linkages between multi-scale environmental gradients, riparian vegetation communities and stream habitat for endangered fishes.

Significance of Project

The interior Columbia and Missouri River basins are home to two endangered species act protected species, bull trout (Salvelinus confluentus) and steelhead (Oncorhynchus mykiss). As a part of the PACFISH and INFISH Biological Opinions, federal agencies managing land within the interior Columbia and upper Missouri River basins must monitor the status and trend of stream and riparian habitats. This monitoring, conducted by the USDA Forest Service PIBO EMP has provided a rich dataset on the composition of riparian vegetation and structure of instream fish habitat on federal lands of the interior Pacific Northwest. We use this data to ask four questions: 1. Do distinct riparian vegetation communities exist within the Columbia and Missouri River basins? 2. What environmental filters shape community assembly into these communities? 3.  4. Do vegetation communities correspond to distinct differences in stream habitat? 


In riparian ecosystems, multi-scale environmental filters shape the composition and structure of vegetation. Filters are environmental, physical or biotic parameters that restrict the species that can colonize and persist at a given location from within larger regional species pools. Riparian vegetation communities, while a product of environmental filters, may also correspond to distinct differences in stream habitat parameters such as bank stability, instream wood and pool dynamics. There have been few regional-scale classifications of stream networks based on riparian vegetation. In this study we examined how environmental filters at the landscape, watershed-buffer and stream reach scales correspond to riparian plant community composition across the U.S. interior Pacific Northwest. We used ordination to correlate vegetation composition to environmental filters at the landscape, watershed and stream scales and identified unique vegetation communities using cluster analysis and indicator species analysis. We also used partial redundancy analysis to see how environmental filters at multiple scales explained vegetation composition.


Vegetation community composition was strongly correlated to landscape-scale environmental filters including elevation, precipitation and temperature. Watershed scale environmental filters that were correlated to vegetation composition included the proportion of each watershed that were grazed and forested. The stream scale variables, bank angle, percent undercut banks and wood frequency were all correlated to riparian vegetation composition, but less strongly than watershed- and landscape-scale filters. Landscape scale filters explained most of the variability in the vegetation data. We identified ten distinct vegetation communities within three broad classes: forested, shrub-forb and meadow systems. Forested systems generally occurred at higher elevations with moderate to high precipitation. Shrub-forb systems were dominated by Salix species and appeared to be early-successional forested systems or persist through environmental conditions that preclude forest establishment. Meadow systems corresponded to high water tables and/or high grazing activity. Between riparian vegetation communities there were significant differences in stream-scale environmental filters that correspond directly to instream habitat quality: stream hydraulic radius, gradient, sinuosity, percent undercut banks, median particle size and wood frequency.


This study shows that multi-scale environmental filters are directly related to riparian vegetation composition and correspond to distinct riparian plant communities. We conclude that because multi-scale environmental filters directly affect riparian vegetation that in turn affects stream habitat, riparian vegetation can be used as both an indicator of current watershed conditions and potential future trajectories of instream integrity.

Related Links and Future Work

USDA PACFISH/INFISH Biological opinion


Papers and presentations tied to this project are available at N. Hough-Snee's figshare profile.

Project Outputs

Hough-Snee, N., B.B. Roper, J.M. Wheaton, R.L. Lokteff. Submitted. The role of environmental filters in controlling the distribution of riparian plant communities within the Columbia and Missouri River basins. Freshwater Biology.

Presentations from this Project

Society of Wetland Scientists Pacific Northwest Chapter meeting, Boise, ID 2012 

USU Watershed Sciences Graduate Symposium Logan, UT, 2013 

Datasets Associated with this Project

Data will be available as an online supplement to a peer-reviewed manuscript (Hough-Snee et al., submitted Freshwater Biology) through N. Hough-Snee's figshare profile. Raw PIBO EMP data is currently available directly from the USDA PACFISH/INFISH Biological opinion effectiveness monitoring program. 

Project Details

Project PI:  Brett RoperProject Personnel from ET-AL: Nate Hough-SneeJoe Wheaton (Co-PI & NH-S PhD Supervisor)
Project Collaborators: Brett Roper
Funding Source: USDA Forest Service provides salary support to NH-S
Project Start Date: May 2012
Project End Date (anticipated): May 2013