Comparison of soil infiltration rates in burned and unburned mountainous watersheds

Steady‐state infiltration measurements were made at mountainous sites in New Mexico and Colorado, USA, with volcanic and granitic soils after wildfires and at comparable unburned sites. We measured infiltration in the New Mexico volcanic soils under two vegetation types, ponderosa pine and mixed conifer, and in the Colorado granitic soils under ponderosa pine vegetation. These measurements were made within high‐severity burn areas using a portable infiltrometer with a 0·017 m2 infiltration area and artificial rainfall rates ranging from 97 to 440 mm h−1. Steady‐state infiltration rates were less at all burned sites relative to unburned sites. The volcanic soil with ponderosa pine vegetation showed the greatest difference in infiltration rates with a ratio of steady‐state infiltration rate in burned sites to unburned soils equal to 0·15. Volcanic soils with mixed conifer vegetation had a ratio (burned to unburned soils) of at most 0·38, and granitic soils with ponderosa pine vegetation had a ratio of 0·38. Steady‐state infiltration rates on unburned volcanic and granitic soils with ponderosa pine vegetation are not statistically different. We present data on the particle‐size distribution at all the study sites and examples of wetting patterns produced during the infiltration experiments. Published in 2001 John Wiley & Sons, Ltd.