Attempts to classify the “health” or “functionality” of riparian systems typically focus on morphology of the stream channel and associated banks, and attempt to relate this information to the potential hydrologic activity of the stream. In this paradigm, riparian vegetation composition is often viewed as a consequence of stream morphology, or, alternatively, a direct result of management actions (i.e. livestock grazing). This view of riparian plant community ecology is incomplete, in that it does not take into consideration other site factors (e.g. soil texture, limiting layers…) which may influence the presence or absence of a given plant community type. At present, there is little empirical information on the site factors required for establishment and persistence of specific plant community types in riparian zones in southeast Oregon. In upland areas, the type of “ecological site” denotes the particular suite of environmental conditions present at a given site and serves as a useful reference for deducing the range of plant community types capable of existing at that site. It is our view that a similar approach applied to riparian areas may increase our understanding of plant community dynamics in these systems. Our overall aim in this project is to delineate environmental factors that influence plant community composition of riparian areas in southeast Oregon. We will simultaneously examine the specific and interactive effects of management actions.
Fieldwork will take place on Rattlesnake Creek, Sawtooth Creek, and Nicoll Creek, in northern Harney County, OR during the 2000 and 2001 growing seasons. We will attempt to sample a set of sites that represents our interpretation of the range of plant community types extant on a given drainage. At each site we will estimate vegetation composition and record soil properties, stream characteristics. Management information will be obtained from the appropriate management agency or landowner. We will attempt to sample a total of 25 sites per creek during the 2000 and 2001 growing seasons, for a total of 150 sites.
In the data analysis phase of this project we will use statistical procedures to group similar plant communities and define important environmental variables which influence plant community type (e.g. soil texture, soil moisture, elevation). Similar procedures will be used to determine what environmental factors most influence plant species composition within a given community type.
The end product of our efforts will be a publication detailing riparian plant community types along with the environmental and management factors influencing plant species composition. Information gained from this effort should allow managers to more accurately separate the influences of management actions and site conditions on plant community dynamics, and should serve as a useful reference for stream rehabilitation/re-vegetation efforts.
If you are interested in this study, contact Chad Boyd.