Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: December 9, 2008
Publication Date: December 9, 2008
Citation: Pierson Jr, F.B., Stone, J.J. 2008. Hydrologic and Erosional Impacts of Altered Fire Regimes and Plant Invasions. Wildfire and Invasive Plants in American Deserts, Society for Range Management, Reno, NV, December 9-11, 2008. Technical Abstract: Healthy rangeland ecosystems consist of functional and structural biotic communities that limit soil redistribution and loss by water. Healthy rangelands effectively capture, store, and release water, resist alteration of these functions, and recover these capacities post-disturbance. Rangeland fire is a natural disturbance and its occurrence within consistent return intervals is commonly associated with healthy functioning rangelands. Altered fire regimes can have detrimental effects on vegetative structure and hydrologic function of rangeland communities. Fire or the lack of burning can increase the abundance of invasive species, which in turn may alter fire behavior and fire regimes. Such landscape scale alterations often sustain the presence of invasive species and the fire regimes that propagate them. The hydrologic and erosional responses to these changes vary with pre- and post-fire plant communities, climate, geomorphology, and soil characteristics. Conversion of shrublands and perennial grasslands to annual grass communities commonly facilitates more frequent and intense fires. Conversely, long-term fire suppression on shrub steppe can facilitate increased tree dominance, decreased shrub and herbaceous species coverage, and increased bare soil exposure. In both scenarios, increased bare soil exposure amplifies surface runoff and soil loss at the hillslope scale from rainsplash, sheetwash, and concentrated flow processes. Under some conditions simultaneous vegetation invasions and drought conditions have been associated with increased frequency and spatial expanse of severe wildfires. These concurrent changes at the landscape level increase the risk of watershed scale mass flooding and erosion events. Current hydrologic and erosion risk assessments are hampered by the vastness of species invasions across bio-regions, the small scales of historic studies, and lack of long-duration experiments. Our advancement in the understanding of fire and invasive species impacts on hydrologic processes requires further research on bio-region specific invasions (fire and non-fire related) across multiple spatial and temporal scales.