Document: JON-3-34-46

Influence of precipitation timing on sagebrush steppe vegetation.

BATES, J.* ¹, T.SVEJCAR ¹, R.ANGELL ¹ and R.MILLER ^1,2

USDA-Eastern Oregon, USA ¹
Oregon State University, Corvallis, OR 97331 USA ²

Abstract:
Climatic variability has historically influenced plant community dynamics and distribution in the Great Basin of the United States. During the past 2 million years plant communities in the region have been less stable than was previously assumed. Thus, impacts of short and long-term climate shifts are relevant to understanding and managing Great Basin ecosystems. The objective of this study was to assess effects of altered precipitation patterns on plant community dynamics in the sagebrush steppe of the Northern Great Basin. Five rainout shelters were constructed to control season and amount of precipitation at the Eastern Oregon Experimental Range in Burns. Precipitation under the shelters was applied with a sprinkler system. Treatments under the shelter were Winter, Spring, and Current. The Winter treatment received 80% of its moisture between October and March. The Spring treatment received 80% of its moisture between April and July. The Current treatment received moisture conforming to long-term distribution patterns. Shelter treatments received 205 mm of moisture annually. A Control treatment was located outside each shelter and received natural precipitation. Herbaceous cover increased in all treatments between 1994 and 1999. Bareground was greatest in the Control as a result of lower litter cover and/or greater plant cover in the shelter treatments. In the shelters, bareground in the Spring treatment was significantly greater (P< 0.01) than Current and Winter treatments. In 1998 and 1999 herbaceous cover and production were significantly lower (P< 0.01) in the Spring versus other treatments. The Winter treatment was most favorable to annual production and cover indicating the importance of winter and late spring precipitation to this functional group. There was little emergence and growth of annuals in the Spring treatment during the study. Herbaceous reproductive success and seed weights were significantly lower (P< 0.01) in the Spring versus other treatments. Sagebrush cover increased slightly but did not differ among treatments between 1994 and 1999. Sagebrush reproduction success and floret weight were significantly greater in the Spring versus other treatments in 1998 and 1999. The results indicated sagebrush was less influenced by short-term climate shifts than was the herbaceous component.

Keywords: Great Basin, climate change, sagebrush. precipitation

This abstract is being presented at: 8:30 AM in session:
Oral Session #43: Plant Community Responses to Climate Change.