WATER-STRESS AND USE OF SUMMER PRECIPITATION IN A GREAT-BASIN SHRUB COMMUNITY

1. Seasonal patterns of water stress (determined from predawn xylem pressure potentials) and relative use of summer precipitation (determined from hydrogen isotope composition) varied intraspecifically and interspecifically in a Great Basin shrub community. 2. The development of water stress during the dry season from June to July was positively correlated with the use of summer precipitation in August. The smallest plants generally developed the greatest water stress and took up the most summer precipitation, presumably due to being more dependent on shallow roots. 3. Among mature shrubs examined, moisture from summer precipitation was taken up by Chrysothamnus viscidiflorus and Artemisia tridentata, but not by C nauseosus, Juniperus osteosperma and Tetradymia canescens. 4. For shrub species that are deeply rooted at maturity, such as C nauseosus, the quantity and timing of available soil moisture is different for small establishing plants as compared to large reproductively mature plants.