Influences of Riparian Vegetation on Aquatic Ecosystems with Particular Reference to Salmonid Fishes

--The riparian zone has important influences on the total stream ecosystem including the habitat of salmonids. Shade and organic detritus from the riparian zone control the food base of the stream and large .Toody debris influences channel morphology. Temporal and spatial changes in the riparian zone, the indirect influences of riparian vegetation on salmonids, and the effects of man's activities are discussed. INTRODUCTION lo/HAT IS RIPARIAN VEGETATION? Streamside vegetation strongly influ­ Riparian vegetation is at the interface ences the quality of habitat for anadromous between aquatic and terrestrial environments. and resident coldwater fishes. Riparian veg­ It has, therefore, been defined and examined etation provides shade, preventing adverse from a number of perspectives. Plant ecolo­ water temperature fluctuations. The roots of gists speak in terms of riparian species trees, shrubs, and herbaceous vegetation sta­ and plant communities. The riparian zone bilize streambanksproviding cover in the form may also be defined geographically in terms of overhanging banks. Streamside vegetation of topography, so.ils, and hydrology. We pre­ acts as a "filter" to prevent sediment and fer to take a functional approach; that. is, debris from man's activities from entering to consider riparian vegetation as any extra­ the stream. Riparian vegetation also directly aquatic vegetation that directly influences controls the food chain of the stream eco­ the stream environment. system by shading· the stream and providing organic detritus and insects for the stream Consequently, in defining riparian vege­ organisms. tation we must consider the full scope of its biological and physical influences on the stream. Riparian vegetation regulates the lContributed paper, Symposium on the energy base of the aquatic ecosystem by shading Importance, Preservation and Management of the and supplying plant and animal detritus to the Riparian Habitat, July 9, 1977, Tucson, Arizona. stream. Shading affects both stream temper­ 2 atu~e and light available to drive primary The work reported in this paper was production; therefore, the balance between supported in part by National Science Foun­ autotrophy and heterotrophy is determined by dation Grant No. 7602656 to the Coniferous multiple functions of riparian vegetation. Forest Biome and Grant No. BMS75-07333 to the River Continuum Project. This is con­ Although imperfect, the stream order tribution No. 283 from the Coniferous Forest system(Leopold et al. 1964) is a useful way Biome and No. 5 from the River Continuum to classify elements of a drainage system. Project. In small and intermediate-sized streams (up 3 Research Fishery Biologist, USDA Forto about fourth-order) in the Pacific North­ est Service, Pacific Northwest Forest and west, riparian vegetation exercises important Range Experiment Station, Forestry Sciences controls over physical conditions in the stream Laboratory, Corvallis, Oregon 97331; Research environment. Rooting by herbaceous and woody Associate and Research Assistant Professor, vegetation tends to stabilize streambanks, Oregon State University, Corvallis, 97331. retards erosion, and, in places, creates over­