Soil Erosion after Recent Wildfires in Southwest USA Forests – Implications for Soil Function Recovery.

In the past two decades wildfires in the Southwest USA have increased in size and severity due to weather conditions that are hotter, drier, and windier, and fuel buildups that are unprecedented in this and the past century. Loss of organic matter horizons, development of soil water repellency, steep mountain slopes, and intense Monsoon rainfall have altered hydrologic function and produced erosion rates of 370 Mg ha^-1 or more. Development of rills and gullies on exposed mineral soil has led to loss of entire soil horizons, channel incision, flash flooding, drying of remaining profiles, loss of tree seed sources, and increased risk of slope failure. Forest recovery is limited by seedling availability, semi-arid climate, cold weather, high altitude, high seedling mortality, and sprouting of chaparral-type plant species. Realistically, soil and forest recovery will take several centuries or more. This paper examines some of the wildfires of the past 16 years and the post-fire erosion that followed.