|Miller, Richard - OREGON STATE UNIVERSITY|
Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 8, 1999
Publication Date: N/A
Interpretive Summary: The arid rangelands of the world are known for their extreme year-to-year variation in climate. Rangeland managers are faced with the difficult task of trying to separate the impacts of climate on rangelands from those impacts that are a result of management. Unfortunately, there is relatively little information available for many aspects of climate. In the case of the Great Basin, it has been proposed that global change may influence the timing of precipitation more than the actual amount. Precipitation timing is a very difficult variable to control on a scale necessary for assessment of impacts on rangeland plant communities. In this paper we describe a procedure that allows one to control precipitation timing for intact native plant communities. The approach uses structures to exclude natural rainfall and overhead sprinkles to apply precipitation at specified times.
Technical Abstract: Seasonal distribution of rainfall is thought to be important in structuring arid and semi-arid plant communities. Controlled studies of rainfall distribution have proven difficult, especially at the scale necessary to evaluate plant community changes. Simply comparing years with different rainfall distributions is problematic because rainfall amounts are seldom constant, and there is no way to factor out other climatic variables (such as temperature). We describe an approach for studing rainfall distribution using large (12x30m) fixed-location rain shelters. Rainfall was excluded and water was applied to three zones within each of five individual rain shelters. The treatments applied to the watering zones were: 1) average precipitation distribution from long-term records (50% from November to March, 30% April to June, and 20% divided among July, August, and October), 2) spring distribution (80% from April to July) and 3) winter distribution (80% from November to March). This approach allows for a comparison of treatments where only rainfall distribution is altered. Factors to consider in designing a study of this nature include: cost of structures and plot size necessary, quality of water to be applied to plots, differential animal use of treatments, and management of watering treatments.