Simulating small mammal effects on grass-shrub ecotones in arid ecosystems

Title	Simulating small mammal effects on grass-shrub ecotones in arid ecosystems
Publication Type	Conference Paper
Year of Publication	2002
Authors	Hochstrasser T., Peters DC, Bestelmeyer BT
Conference Name	17th Annual Symposium, US-International Association for Landscape Ecology
Date Published	April 23-26, 200
Conference Location	Lincoln, NE
ARIS Log Number	144658
Abstract	Several processes leading to shrub encroachment within semiarid and arid grasslands have been identified. However, the role of small animals in shifting dominance between grasses and shrubs at their ecotones has not been well studied, especially in combination with other factors, such as drought, cattle grazing, and soil properties. These potentially interacting factors may have contributed to contradictory results of studies of animal effects on shrub encroachment. The objective of this study was to evaluate the relative importance of small mammals, climate, and soil properties to shifts in the location and composition of grass-shrub ecotones in the Chihuahuan Desert. We used a simulation model to integrate the effects of these factors on the recruitment, growth, and survival of creosotebush (Larrea tridentata), mesquite (Prosopis glandulosa), and black grama (Bouteloua eriopoda). In particular, we were interested in the positive and negative effects of animals on shrub recruitment and grass survival. Simulated timespans over which shrub encroachment occurred into black grama grassland were different for the two shrub species. Effects of animals varied with the shrub and animal species involved. Using these simulation results, we developed a framework for understanding and predicting the role of small mammals in shrub encroachment.