PARENT SESSION
Thursday, August 10, 1:30-5:00 pm
COS 102 - Arid ecosystem ecology
L-14, Lobby Level, Cook Convention Center
Presiders: J Fehmi
Wind erosion and vegetation interactions in desert grassland ecosystems.
Hartman, Lorelei*,1, Epstein, Howard1, Okin, Gregory1, Li, Junran1, 1 University of Virginia, Charlottesville, VA, USA
ABSTRACT- Desert grassland degradation is common in many arid environments and is related to increasing shrub coverage, declines in grass species and loss of soil nutrients. Wind erosion can contribute to this degradation by eroding the soil surface and depleting soil nutrients. Wind eroded soils are trapped beneath shrub canopies, creating "islands of fertility" beneath shrubs, while grass species are likely abraded or buried as a result of erosion and deposition. We have established three treatment blocks on the Jornada Experiment Range in southeastern New Mexico in a predominantly grassland habitat (interspersed with some shrub cover) to examine interactions among wind erosion, vegetation and soil nutrient distribution in the Chihuahuan desert. Each block includes five 25x50m treatment plots with different levels of vegetation removed (100%, 75%, 50%, 25%, and 0% - control) to stimulate wind erosion. Dust flux, plant community composition and coverage (lateral and fractional), and soil nutrient distribution are being monitored on and immediately downwind of treated areas. To understand direct impacts of abrasion and deposition on plants, individual grasses and shrubs have been selected for monitoring of leaf-level photosynthesis rates. Preliminary results indicate an exponential increase in dust flux with decreasing lateral coverage. We also found a possible threshold level of vegetation coverage necessary to prevent this exponential increase in wind erosion. Leaf level photosynthesis rates were higher for shrubs than grasses, and were lower for grasses downwind of the 100% removal areas. Additionally, a decrease in grass coverage downwind of treated areas suggests that community composition changes are occurring downwind from eroding areas after just two windy seasons. These preliminary results indicate a significant role for wind erosion in grassland degradation and conversion to shrub dominated habitat.
Key words: wind erosion, desert grassland, desert ecology