Ecological Restoration

Effects of Land Management Disturbances on Headwater Riparian Ecosystems.
Walter J. Edelen, Graduate Research Assistant, Department of Range Resources.
Funded in part through the University of Idaho Experimental Forest.

Project summary

Riparian habitats in forest and meadow zones were examined on six northern Idaho headwater streams within the University of Idaho Experimental Forest. Timber harvesting, domestic livestock grazing, and transportation systems have influenced these watersheds for nearly a century. Representative cross-sectional transects were established to characterize morphological, floristic, and edaphic features for comparisons of reference and disturbed riparian ecosystems. Assessments of current riparian conditions and management alternatives were formulated through riparian-wetland guides designed by the United States Bureau of Land Management and the Forest Service. Grazed meadow and forest streams were 32% wider than ungrazed reaches. Mean bank angles for grazed streams were 15 degrees wider than undisturbed streams, exhibited poor bank stability, and had greater potential for erosion. High concentrations of fine sediments were found throughout, or immediately below, all grazed sections. Grazed meadow streams averaged nearly 80% fine sediments. In contrast, undisturbed forested reaches had 10% more bank undercuts, less fine sediments, stable banks, significantly greater shorewater depth, and longer seasonal flow. Evaluations of current stream conditions suggest that continuously disturbed riparian ecosystems may obstruct natural abilities for normal functional processes such as sediment filtration and streambank aggradation. Ecosystem-based strategies are needed to restore riparian areas to stable and self-regulating ecosystems.

Abstract. 38th annual meeting of the Idaho Academy of Science, April 4-6, 1996.