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United States Department of Agriculture

Agricultural Research Service

Title: The Effect of Herbaceous Species Removal, Fire, and Cheatgrass (Bromus tectorum) on Soil Water Availability in Sagebrush Steppe.

Authors
item Whittaker, Alison - UTAH DIV. WILDLIFE RESOUR
item Roundy, Bruce - BRIGHAM YOUNG UNIVERSITY
item Chambers, Jeanne - USDA-FOREST SERVICE-RMRS
item Meyer, Susan - USDA-FOREST SERVICE-RMRS
item Blank, Robert
item Kitchen, Stanley - USDA-FOREST SERVICE-RMRS
item Korfmacher, John - USDA-FOREST SERVICE-RMRS

Submitted to: Forest Service General Technical Reports
Publication Type: Proceedings
Publication Acceptance Date: June 17, 2008
Publication Date: November 15, 2008
Citation: Whittaker, A., Roundy, B., Chambers, J., Meyer, S., Blank, R.R., Kitchen, S., Korfmacher, J. 2008. The Effect of Herbaceous Species Removal, Fire, and Cheatgrass (Bromus tectorum) on Soil Water Availability in Sagebrush Steppe. Shrublands Under Fire: USDA-FS, Rocky Mountain Research Station RMRS-P-52. Forest Service General Technical Reports.

Interpretive Summary: There is limited research that explains why cheatgrass has been a successful invader in Great Basin sagebrush communities. We quantified the effects of herbaceous vegetation removal and fire on available water for cheatgrass invasion, as well as effects of cheatgrass itself, on nine sites in Nevada and Utah. Vegetation removal plots had 7 days longer subsurface soil water availability than intact plots the first year after removal. Burned plots had 4 to 6 days longer subsurface soil water availability than unburned plots. Cheatgrass establishment was limited, especially at the Utah sites, and did not significantly affect soil water availability. Soil water resources may be increased by disturbance, higher annual precipitation, or both and thereby facilitate weed invasion.

Technical Abstract: Over the past several decades, cheatgrass (Bromus tectorum) has been continually expanding in the sagebrush steppe ecosystem. There has been very little research that examines why cheatgrass is able to invade these communities. To determine the effects of herbaceous vegetation removal and fire on available water for cheatgrass invasion, as well as effects of cheatgrass itself, we measured spring soil moisture and vegetation cover on nine sites in Nevada and Utah. Total time of soil water availability was calculated for 1 April through 30 June in 2002 and 2003 on plots that were left intact, sprayed with an herbicide to kill all herbaceous vegetation, burned, or both burned and sprayed in 2001. Soil water was also measured on subplots either left unseeded or seeded to cheatgrass in fall 2001. The number of days that soil moisture was available increased with site elevation and annual precipitation. Time of surface soil (1 to 3 cm) water availability was increased by 12 days in a wetter year (2003) compared to a drier year (2002) and was not significantly affected by disturbance. Time of subsurface soil water availability (13 to 15 and 28 to 30 cm) was increased more by disturbance than seasonal precipitation. Vegetation removal plots had 7 days longer subsurface soil water availability than intact plots the first year after removal. Burned plots had 4 to 6 days longer subsurface soil water availability than unburned plots. Cheatgrass establishment was limited, especially at the Utah sites, and did not significantly affect soil water availability. Soil water resources may be increased by disturbance, higher annual precipitation, or both and thereby facilitate weed invasion.

Last Modified: 4/18/2014
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