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AN APPROACH TO ASSESSING THE CONDITION OF RIPARIAN PLANT COMMUNITIES IN THE JOHN DAY AND DESCHUTES RIVER BASINS OF EASTERN OREGON
Citation:
Magee, T. K., P L. Ringold, AND M. Bollman. AN APPROACH TO ASSESSING THE CONDITION OF RIPARIAN PLANT COMMUNITIES IN THE JOHN DAY AND DESCHUTES RIVER BASINS OF EASTERN OREGON. Presented at Reseach Natural Areas Association Conference, Cape Canaveral, FL, October 3-6, 2001.
Description:
Riparian vegetation represents unique plant communities and provides a variety of ecosystem services that influence in-stream condition. This research develops methods and indicators for evaluating vegetation condition. A key indicator of riparian vegetation condition is the degree of invasion by alien plant species. We sampled vegetation along 15 low order streams in eastern Oregon. Data collected at each stream included presence of all species occurring in a 900 m long transect paralleling the stream course, and the abundance of dominant species in several 20 x 30 m plots perpendicular to the stream. Using cluster analysis, indicator-species analysis, ordination, and aerial photo interpretation, we identified and characterized species assemblages. Alien species invasion along each stream reach and within each assemblage was evaluated using: 1) percentage of alien vs. native species, 2) overall abundance of alien compared to native species, 3) perturbations of vegetation structure or composition associated with the influx of alien species, and 4) a preliminary index of invasion integrating frequency and abundance of alien species weighted by rankings for invasiveness of individual alien species. Potential applications of this approach for restoration, assessment, and monitoring in natural areas management are evaluated.