PARENT SESSION
Symposium #18: Understanding and Restoring Riparian Ecosystems at Risk: The Great Basin Ecosystem Management Project.

Organized by: JC Chambers and JR Miller
Wednesday, August 7. 8:00 AM to 11:30 AM. Turquoise Ballroom, TCC.

Riparian vegetation dynamics: Effects of geomorphic processes, flow regimes, and groundwater systems.

Korfmacher, John^*,1, Chambers, Jeanne¹, Miller, Jerry², Tausch, Robin¹, Germanoski, Dru³, ¹ USDA Forest Service, Reno, NV² Department of Geoscience and Natural Resource Management, Cullowhee, NC³ Geology and Environmental Geoscience, Easton, PA

ABSTRACT- The structure and dynamics of riparian ecosystems in upland watersheds of the central Great Basin are influenced by both past and present hydrogeomorphic processes. Vegetation patterning along stream systems is related to valley characteristics and historic landforms. Cross-valley alluvial fans that formed almost 2000 years ago in many of the watersheds have resulted in increased valley widths and finer soil textures in stream reaches immediately above the fans. Where fans are coincident with high water tables, these reaches are also characterized by meadow vegetation and broader riparian zones. Reaches adjacent to, and immediately downstream of the fans have woody riparian vegetation, narrow riparian zones, and steep transitions between riparian and upland vegetation. The vegetation structure of individual stream segments/reaches is related to channel slope, substrate characteristics, and width/depth ratios. Woody riparian vegetation types generally occur along stream channels with steeper slopes, coarser bank textures, greater channel particle D₅₀, and higher width/depth ratios than meadow vegetation types. Individual riparian species and vegetation types are closely related to depth to water table or terrace height above the stream channel. Episodic high flows can result in stream incision, changes in channel form, and lowered water tables. Knowledge of the relationships among vegetation dynamics and the hydrogeomorphic regime can be used to determine recovery potential and select appropriate restoration treatments.

KEY WORDS: riparian ecology, alluvial fans, stream morphology, Great Basin