How Will Global Climate Change Affect Shrub-Grass Relationships in Arid Lands?
Global climate models predict regional changes in average seasonal precipitation, but few experimental studies have addressed how changes in the delivery of precipitation within a season affect ecosystem responses in arid lands. Initial findings in our rain modification study during the very dry New Mexico summer of 2003, indicate that changes in the distribution of an additional 60 mm of precipitation had a significant effect on ecosystem function. Mesquite shrubs, which are encroaching on these formerly grass-dominated systems, were able to use water from both small frequent rainfall events and large infrequent rainfall events, with the most positive responses occurring with the latter. By contrast, biological soil crust communities, which colonize surface soil and are essential in these arid regions for minimizing soil erosion, benefited from smaller more frequent events. This study at the Jornada LTER, in collaboration with the USDA-ARS led by Keirith Snyder, will continue over a n
