|Miller, Richard - OREGON STATE UNIV|
|Bailey, Roxanne - OREGON STATE UNIV|
Submitted to: Eastern Oregon Agricultural Research Center
Publication Type: Experiment Station
Publication Acceptance Date: January 15, 1998
Publication Date: June 1, 1998
Citation: BATES,J.D., SVEJCAR,A.J., MILLER,R.F., ANGELL,R.F., BAILEY,R., INFLUENCE OF PRECIPITATION TIMING ON SAGEBRUSH/BUNCHGRASS VEGETATION, EASTERN OREGON AGRICULTURAL RESEARCH CENTER, 1998, SPECIAL REPORT 991. PP. 34-44. Interpretive Summary: The Great Basin region of the western U.S. has experienced large swings in climate over the past 10,000 years. There have been much shorter term cycles that may result in weather changes over 10 - 25 year time periods. These cycles are typical of the region and will occur independently of any larger scale global change. We used rain shelters and a sprinkler system to alter precipitation patterns in a sagebrush steppe community. Our results suggest that this plant community does not change quickly even if precipitation timing is altered. We did find that annual forbs are favored by winter as compared to spring precipitation, and that plant cover is higher with winter (compared to spring) precipitation. This study is ongoing, and the results should help land managers better understand climatic impacts on sagebrush steppe plant communities.
Technical Abstract: The objective of this study has been to monitor the effects of altered precipitation patterns on plant community dynamics in the sagebrush steppe. Plant community response to altered precipitation patterns were assessed by monitoring plant species cover and density, biomass production, phenological development, and root growth. Five rainout shelters, 100 x 40 ft., were used to control season and amount of precipitation. Precipitation treatments under each shelter are labeled ¿winter¿, ¿spring¿, and ¿current¿. Annual forbs were the most responsive to different treatments. Annual forb density and cover have been consistently lower in the spring treatment compared to the other treatments in all years. Bareground tended to be greater in the spring treatment than in winter and control treatments since May, 1996. Sagebrush phenology has been delayed in the spring treatment through floral shoot development. However, by the ephemeral leaf drop stage there have been few differences in sagebrush phenology among the treatments. In all treatments, root activity appears to be correlated to soil moisture conditions particularly in the upper (10-20 cm) soil profile. during periods of higher moisture availability root activity increases. Although there has been a lack of any consistent treatment effects it does appear that the spring treatment may be allocating more resources to below ground structures.