Fire and vegetation type effects on soil hydrophobicity and infiltration in the sagebrush-steppe: I. Field analysis

Abstract

Soil water repellency, infiltration, and fire severity were evaluated at 235 locations within a sagebrush-steppe ecosystem in southern Idaho, USA, after a 78,000ha wildfire. Fire frequency in the sagebrush-steppe has increased dramatically in the last century due to the proliferation of introduced annual weeds. Wildfire in shrub-steppe can increase runoff and erosion by decreasing vegetation cover and increasing soil hydrophobicity. Soil water repellency was measured with the water drop penetration time (WDPT) test and relative infiltration rates were measured by the mini-disc infiltrometer (MDI). Shrub-dominated locations showed highest water repellency in areas of moderate fire severity and infiltration rate was inversely related to distance from individual sagebrush plants. Highest water repellency in grass-dominated areas was also associated with moderate fire severity. Likewise, the lowest relative mean infiltration rates occurred in shrub-dominated or grass-dominated areas of moderate fire severity. These findings indicate that land management strategies should be targeted towards moderate fire severity areas.