The 2008 Joint Meeting of the Society for Range Management and the America Forage and Grassland Council. |
Wednesday, January 30, 2008
43
Channel Geomorphologic Changes and Hillslope Soil Movement Following Juniper Treatment on Camp Creek Paired Watershed Study
Michael Fisher, Forest Resources Technology Program, Central Oregon Community College, 2600 NW College Way, Bend, OR 97701, Tim Deboodt, OSU Extension Service, Oregon State University, 498 SE Lynn Blvd, Prineville, OR 97754, and John Buckhouse, Rangeland Ecology and Management, Oregon State University, Corvallis, OR 97331.
Western juniper is encroaching into sagebrush/grass communities in the intermountain west with a correlated reduction in herbaceous ground cover. This potential loss of herbaceous ground cover results in reduced infiltration rates and increased overland flow and soil loss. Increased hillslope erosion and overland flow enter the channel with increased energy and may modifying channel banks and bed. A paired watershed study for the purpose of monitoring effects of juniper treatment on watershed hydrology and geomorphology was established in 1994 in the Camp Creek drainage, a tributary to the Crooked River . In October of 2005, following 10 years of calibration, one of the two watersheds was treated by cutting the western juniper.
Monitoring methods consisted of annual and semiannual measurements of hillslope soil movement and channel morphology (including total cross-sectional area, scour and deposition). Changes in channel morphology were determined using 25 permanent, channel cross-section plots per watershed. Hillslope erosion processes were determined using 12 transects of 3 sediment stakes per watershed, located within gullies of subwatersheds.
Monitoring methods consisted of annual and semiannual measurements of hillslope soil movement and channel morphology (including total cross-sectional area, scour and deposition). Changes in channel morphology were determined using 25 permanent, channel cross-section plots per watershed. Hillslope erosion processes were determined using 12 transects of 3 sediment stakes per watershed, located within gullies of subwatersheds.
Pre-treatment data showed the two study areas to be well correlated with regards to soil movement, both within the main channels and in the subwatersheds (hillslopes). Some of the geomorphometric properties are similar (not statistically different) and differences in other parameters can be explained. Following 2 years of Post-treatment monitoring, data analysis shows how channels and hillslope erosional processes respond to changes in vegetative conditions.