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Title: Ecohydrological consequences of grasses invading shrublands: A comparison of cold and warm deserts

Author
item WILCOX, BRADFORD - Texas A&M University
item TURNBULL, L - Arizona State University
item YOUNG, MICHAEL - University Of Texas
item Williams, Christopher - Jason
item RAVI, SUJITH - University Of Arizona
item Seyfried, Mark
item BOWLING, DAVID - University Of Utah
item Scott, Russell - Russ
item CALDWELL, TODD - Desert Research Institute
item WAINWRIGHT, JOHN - University Of Sheffield
item GERMINO, MATTHEW - Idaho State University

Submitted to: Trans American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 10/16/2010
Publication Date: 12/13/2010
Citation: Wilcox, B.P., Turnbull, L., Young, M., Williams, C.J., Ravi, S., Seyfried, M.S., Bowling, D.R., Scott, R.L., Caldwell, T.G., Wainwright, J., and Germino, M.J. 2010. Ecohydrological consequences of grasses invading shrublands: A comparison of cold and warm deserts. Presented at 2010 Fall Meeting, American Geophysical Meeting, San Francisco, California, 13-17 December 2010, Abstract H32B-08.

Interpretive Summary: Exotic grasses are altering native savannas and woodlands across the globe. We summarize the current state of knowledge concerning the ecohydrological consequences of native-shrubland-to-grassland conversion. Our objectives are to understand ecohydrological changes at the local scale, such as soil-water content or hillslope erosion; and whether these small-scale changes have consequences for larger-scale phenomena such as flooding, sedimentation in rivers, groundwater recharge, energy budgets, and weather patterns. In addition, we are interested in identifying gaps in our knowledge and research priorities. Our analysis is based on a synthesis of relevant literature complemented by simulation modeling using HYDRUS-1D and MAHLERAN. In terms of runoff and erosion, we find that the influence of grass invasion on surface runoff and erosion is different for the cold and warm deserts. For cold deserts, runoff and erosion will increase while for the warm deserts the opposite is likely to occur. In particular, the erosion hazard will be greatly amplified on steep slopes (>20%) following burning. In warm deserts, grass invasion may actually reduce runoff and erosion. In terms of the vertical fluxes of evaporation and soil water recharge we find that grass invasion will likely lead to higher soil water recharge in cold deserts but not to the extent that groundwater will be affected for many, many decades and then likely not very much. In warm deserts grass invasion likely has little affect on evapotranspiration fluxes or soil water.

Technical Abstract: Exotic grasses are altering native savannas and woodlands across the globe. We summarize the current state of knowledge concerning the ecohydrological consequences of native-shrubland-to-grassland conversion. Our objectives are to understand ecohydrological changes at the local scale, such as soil-water content or hillslope erosion; and whether these small-scale changes have consequences for larger-scale phenomena such as flooding, sedimentation in rivers, groundwater recharge, energy budgets, and weather patterns. In addition, we are interested in identifying gaps in our knowledge and research priorities. Our analysis is based on a synthesis of relevant literature complemented by simulation modeling using HYDRUS-1D and MAHLERAN. In terms of runoff and erosion, we find that the influence of grass invasion on surface runoff and erosion is different for the cold and warm deserts. For cold deserts, runoff and erosion will increase while for the warm deserts the opposite is likely to occur. In particular, the erosion hazard will be greatly amplified on steep slopes (>20%) following burning. In warm deserts, grass invasion may actually reduce runoff and erosion. In terms of the vertical fluxes of evaporation and soil water recharge we find that grass invasion will likely lead to higher soil water recharge in cold deserts but not to the extent that groundwater will be affected for many, many decades and then likely not very much. In warm deserts grass invasion likely has little affect on evapotranspiration fluxes or soil water.