PARENT SESSION
Poster Session 30: Soil Ecology.
Wednesday, August 4 Presentations from 5:00 PM to 6:30 PM, Exhibit Hall A 1.
Effects of global change on Mojave Desert annual plant communities.
Stacy, Irvin*,1, Zimpfer, Jeff1, Smith, Stanley1, 1 University of Nevada-Las Vegas, Las Vegas, NV
ABSTRACT- Global change has the potential to profoundly affect ecosystems, particularly in arid environments. In the Mojave Desert, some changes that are predicted to occur include increased summer precipitation, increased nitrogen deposition, and continued disturbance of biological soil crusts. At the Mojave Global Change Facility, located in southern Nevada, these changes are simulated in a full factorial design and applied to 14x14-m plots. Treatments include 1) summer irrigation, 2) nitrogen fertilization (10 and 40 kg N/ha/yr), and 3) crust disturbance. To determine the effects of these treatments on annual communities, 25x25-cm subplots were placed in three microsites, including under an evergreen shrub, under a deciduous shrub, and in the interspace between shrubs. Subplots were monitored throughout the growing season for species composition, density, and phenological stage. In addition, plants from the most abundant species were harvested to obtain biomass measurements. All three treatments had significant effects on annual communities, but there were no significant interactions between the treatments. Irrigation treatments decreased plant density from 249 to 224 plants/m2 and biomass from 26.3 to 23.7 g dry mass/m2. Disturbance of the biological soil crust did not affect plant density, but did increase plant biomass from 21.4 to 28.8 g dry mass/m2. Fertilization with 10 and 40 kg N/ha increased density from 209 to 237 and 263 plants/m2, respectively. Biomass was increased from 16.9 to 28.1 and 30.2 g dry mass/m2, respectively. In addition to these community-level responses, species-specific responses will be explored in more detail. These results demonstrate that predicted global changes in the Mojave Desert will likely have pronounced effects on annual plant communities, which in turn will alter ecosystem processes in this arid ecosystem.
Key words: annuals, Mojave Desert, global change, productivity