PARENT SESSION
Symposium #31: Ecological Restoration in a Future Altered Climate .

Organized by: ME Loik and KD Holl
Thursday, August 8. 1:00 PM to 3:45 PM. Leo Rich Theatre.

Effects of altered precipitation on seedling recruitment in arid ecosystems.

Loik, Michael^*,1, ¹ University of California, Santa Cruz, Santa Cruz, CA

ABSTRACT- Anthropogenic increases in atmospheric carbon dioxide are altering global and regional climate patterns. Climate change is expected to result in increases in annual precipitation for much of the United States, with a 50% increase predicted for portions of the arid west by 2095. For arid and semi-arid ecosystems, such increases are likely to affect plant recruitment, population dynamics, community composition, and various ecosystem processes. Seedling recruitment is vulnerable to stresses within the boundary layer microclimate, which are expected to be altered in a future climate. Because arid ecosystems receive a limited number of precipitation events per year, even single additional precipitation events could have significant effects on recruitment. Establishment is often facilitated by the presence of adult nurse plants, whose canopies modify the abiotic microenvironment for seedlings. Hypotheses regarding the effects of increased summer precipitation on seedling recruitment were tested in the western Great Basin Desert, where future summer rainfall is expected to increase. Responses to experimental water additions were compared for Artemisia tridentata and Purshia tridentata, two widespread species of the Great Basin that comprise a large portion of the above-ground plant cover at this site. Results indicate that increased precipitation may be more important for seedlings of A. tridentata compared to P. tridentata, and that the preferred recruitment niche for P. tridentata (gap microsites) may be subject to encroachment by growth of adult A. tridentata in response to increased summer rain. Comparison of plant recruitment success across manipulative atmospheric and climate change experiments can help to identify important factors and processes for future restoration efforts. Moreover, given the cost of large-scale global change experiments, comparison of results on seed dispersal, germination, and seedling establishment from various extant experiments would be highly useful for informing restoration practices for a future, altered climate.

KEY WORDS: Pulse, Artemisia tridentata, Purshia tridentata, Rainfall