Monday, August 4, 2008 - 2:50 PM

OOS 2-5: Paired, competing dryland ecohydrological processes in plants, soils, and water: Woody and herbaceous plants, evaporation and transpiration, and wind and water-driven erosion

David D. Breshears, The University of Arizona

Background/Question/Methods Many patterns, processes and dynamics in dryland ecosystems center around interactions between plants soils and water. The recent emphasis on areas such as ecohydrology and hydropedology highlights the growing recognition of the need to adopt a more interdisciplinary approach to addressing these interfaces. Ecology has focused to a large extent on competition between species or between plant functional types. But abiotic components of ecosystems can also be subject to competing processes. Here I provide an overview of two predominant components for the plants, soils, and water attributes of ecosystems and highlight competing interactions within each attribute, as well as interactions among attributes.

Results/Conclusions For plants, the mosaic of canopy patches associated with woody plants and the intercanopy locations that separate them represent two key components. The major pathways of water loss from dryland systems are related to evaporation and transpiration, which are competing processes. Similarly, soil erosion is driven by both wind and water, and even though these processes are usually treated separately, they are actually competing. Woody plants influence shading patterns, thereby affecting evaporation rates indirectly in addition to directly affecting transpiration. Similarly, woody and herbaceous plants are central drivers of rates of wind and water erosion. These examples highlight how focusing on paired, competing abiotic as well as biotic processes is needed to address ecohydrological challenges in drylands.