PARENT SESSION
Oral Session #25: River and Riparian Restoration I.
Presiding: M.A. Madej
Tuesday, August 6. 8:00 AM to 11:30 AM. Mohave Meeting Room, TCC.
Restoration of riparian corridors and large woody debris in California's hardwood-dominated watersheds.
Opperman, Jeff*,1, Merenlender, Adina1, 1 Dept. of Environmental Science, Policy and Mgmt, Berkely, CA
ABSTRACT- Strategies to restore anadromous fish habitat often focus on the critical influence of riparian vegetation and large woody debris (LWD) on instream habitat. However, most studies of these interactions have been conducted in the conifer-dominated forests of the Pacific Northwest. In California, anadromous fish, such as Steelhead trout (Oncorhynchus mykiss), also utilize Mediterranean-climate, hardwood-dominated watersheds, but very little is known about the influence of LWD on fish habitat in these systems. We seek to guide riparian restoration in hardwood watersheds by assessing existing restoration projects and studying the relationship between riparian forests, LWD, and fish habitat in protected watersheds. Although LWD loading (volume of wood per unit area of channel) in hardwood watersheds was much lower than loading in conifer watersheds, our results indicate that woody debris still provided a major influence on fish habitat in these streams. Pool frequency was positively correlated with LWD loading and, in streams with high levels of wood, LWD was the primary agent of pool formation. While conifer forests can contribute large single pieces of wood that influence pool formation, the comparatively smaller hardwood debris most effectively influenced channel morphology through complex jams composed of both living and dead wood. In five streams with restored riparian corridors LWD frequency increased relatively rapidly (10-20 years), but the volume of wood, size of debris jams, and interaction between LWD and channel form had not yet reached levels found in protected watersheds. Understanding these relationships will help guide the management efforts of agencies and landowners seeking to restore riparian corridors and threatened fish populations within hardwood watersheds.
KEY WORDS: Riparian restoration, wood debris, hardwoods