Tuesday, November 6, 2007
217-1

Soil Morphology and Organic Matter Beneath Cheatgrass-, Sagebrush-, and Bunchgrass-Dominated Shrub-Steppe Vegetation.

Jay B. Norton1, Robert R. Blank2, Thomas A. Monaco3, and Thomas A. Jones3. (1) Dept of Renewable Resources, Univ of Wyoming, 1000 E. University Ave., Laramie, WY 82071-3354, (2) Exotic and Invasive Weeds Research Unit, USDA-ARS, 920 Valley Road, Reno, NV 89512, (3) Forage and Range Research Laboratory, USDA-ARS, 695 N. 1100 E., Logan, UT 84322-6300

Cheatgrass (Bromus tectorum) is an invasive annual grass that increases wildfire frequency, degrades native ecosystems, and threatens agriculture across vast areas of the western U.S. Our research examines how cheatgrass may resist reversion to native shrub-steppe vegetation by altering physical and biological properties of soils. The degree of such alteration may impact success of rangeland restoration. We compared morphology and soil organic matter characteristics in soil profiles and replicated 0- to 10- and 10- to 20-cm surface samples at sixteen cheatgrass-dominated sites and geomorphically paired adjacent sites dominated by native sagebrush-steppe vegetation in Utah, Idaho, Nevada, and Oregon. Sagebrush-steppe vegetation ranged from native bunchgrass-dominated sites to degraded sites with dense shrub cover and little herbaceous cover. Results show differences between sites in soil structure, pH, and the distribution and quality of soil nutrients and organic matter pools. The magnitude of these differences varies with the quality of the native plant community. We suspect that this variation may result from a combination of past site disturbance (e.g., fire frequency, grazing management), the length of time cheatgrass has dominated the site, and basic soil properties that control ecological resistance to change. These factors also likely impact the success of restoration treatments on Great Basin Rangelands.