Invasion of shrublands by exotic grasses: ecohydrological consequences in cold versus warm deserts
Article first published online: 7 AUG 2011
Copyright © 2011 John Wiley & Sons, Ltd.
Special Issue: Ecohydrologic Connections and Complexities in Drylands: New Perspectives for Understanding Transformative Landscape Change
Volume 5, Issue 2, pages 160–173, March 2012
How to Cite
Wilcox, B. P., Turnbull, L., Young, M. H., Williams, C. J., Ravi, S., Seyfried, M. S., Bowling, D. R., Scott, R. L., Germino, M. J., Caldwell, T. G. and Wainwright, J. (2012), Invasion of shrublands by exotic grasses: ecohydrological consequences in cold versus warm deserts. Ecohydrol., 5: 160–173. doi: 10.1002/eco.247
- Issue published online: 2 APR 2012
- Article first published online: 7 AUG 2011
- Manuscript Accepted: 1 JUN 2011
- Manuscript Received: 22 OCT 2010
- water budgets;
- land-cover change;
- invasive species
Across the globe, native savannas and woodlands are undergoing conversion to exotic grasslands. Here we summarize the current state of knowledge concerning the ecohydrological consequences of this conversion for the cold deserts (Great Basin, Colorado Plateau) and the warm deserts (Mojave, Sonoran, Chihuahuan) of North America. Our analysis is based on a synthesis of relevant literature, complemented by simulation modelling with a one-dimensional, soil water redistribution model (HYDRUS-1D) and a hillslope runoff and erosion model (MAHLERAN). When shrublands are invaded by grasses, many changes take place: rooting depths, canopy cover, species heterogeneity, water use, and fire regimes are radically altered. These changes then have the potential to alter key ecohydrological processes. With respect to the processes of runoff and erosion, we find that grass invasion influences cold and warm deserts in different ways. In cold deserts, runoff and erosion will increase following invasion; in particular, erosion on steep slopes (>15%) will be greatly accelerated following burning. In addition, evapotranspiration (ET) will be lower and soil water recharge will be higher—which after several decades could affect groundwater levels. For warm deserts, grass invasion may actually reduce runoff and erosion (except for periods immediately following fire), and is likely to have little effect on either ET fluxes or soil water. Significant gaps in our knowledge do remain, primarily because there have been no comprehensive studies measuring all components of the water and energy budgets at multiple scales. How these changes may affect regional energy budgets, and thus weather patterns, is not yet well understood. Copyright © 2011 John Wiley & Sons, Ltd.