Thursday, August 9, 2007

PS 66-127: Impact of drill seeding and herbicide on slickspot soils

Scott E. Shaff1, Mounir Louhaichi2, David A. Pyke1, and Douglas E. Johnson2. (1) USGS, (2) Oregon State University

Slickspot peppergrass (Lepidium papilliferum (L. Henderson) A. Nels and J.F Macbr.) is a rare plant found on the Snake River Plain in southwestern Idaho. It grows on unique microenvironments within the sagebrush steppe ecosystem that are referred to as slickspots because the soil surface is smooth. The overall goal of our project was to determine if herbicide application and/or seeding native vegetation to control cheatgrass would impact slickspots, the habitat of slickspot peppergrass. Our study area is located in western Elmore County, Idaho and contains approximately 11 ha. The experimental design included four treatments (control, herbicide, seeding using a Truax® minimum till rangeland drill, and herbicide with seeding using a Truax®  minimum till rangeland drill) assigned randomly to 12 subplots (36.5 m by 21.3 m).  During the spring of 2004, 2005, 2006 we collected aerial (1:2400) and near-earth (100 ft. and 150 ft.) photography to map the extent of slickspots within each plot. At the same time we took ground measurements of pre-defined slickspot areas. Images were then processed with VegMeasure or other commercial image processing software packages to generate maps of slickspots for each plot.  When we compared the location and surface area of slickspots measured in 2004, 2005 and 2006, changes were less than 1 m2 per subplot and not statistically significant, which implies that there is no treatment effect on slickspot extent and that slickspots are fairly stable over time. Mapping techniques using aerial photography are much faster than traditional sampling and provide comparable results.

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