EFFECTS OF PRESCRIBED FIRE AND THINNING ON NUTRIENT FATE AND TRANSPORT AND EROSION POTENTIAL IN ERODED PIEDMONT FORESTS OF SOUTH CAROLINA

Prescribed fire, historically a controversial management regime, intends to reduce the duration, intensity and potential of a wildfire event. Although inherent in the landscape since presettlement, wildfire occurrence is a significant threat for the densely populated southeastern U.S. Agricultural and grazing practices in the early 1900s altered much of the southeastern forestland and exposed soils, increasing erosion and nutrient runoff to the extent of severely impaired productivity and a completely altered geomorphology. The resultant landscape was barren, consisting of impoverished soils dissected by 3-20 m gullies that cut almost to the parent material (saprolite). In the early 1930s, nearly 400,000 acres were reserved as the Sumter National Forest (SNF) and subsequently afforested to stabilize the soil, improve water quality and provide forest habitat and wood products.

Management for the restored areas includes thinning and prescribed fire. The effects of these practices are uncertain and controversial; they may have long-term effects on erosional, depositional and hydrologic processes. The principal concern is that fire may destroy the protective organic layer and underlying root mat, thereby increasing the soil’s susceptibility to erosion and nutrient depletion. Since the nutrient capital of these highly eroded soils is contained in the upper layer of soil, oxidation of the forest floor and erosion of mineral soils will influence site productivity and nutrient runoff. Additionally, maintaining the integrity of the slopes is of paramount importance, as erosion would cause increased sedimentation in the streams and adjoining rivers.

This is a full factorial study on the Enoree Ranger District, adjacent to the Broad River in the SNF. Resin disks and soil chemistry analysis will provide assessment tools for nutrient movement and erosion fences will collect sediment washed from slopes to gauge erosion on 24 test plots over a variety of geomorphologic conditions. We hope to use the results from this study to understand how historically exploited or depleted landscapes respond to treatment; these responses provide management guidelines necessary to reduce the health and safety threat of a potential wildfire in a densely-populated area while maintaining a healthy forest ecosystem.