Tuesday, November 6, 2007 - 1:30 PM
214-3

Soil Recovery in Severely Burned Soil Two Years after a Stand-Replacing Wildfire in Central Oregon.

Elizabeth Sulzman1, Jane E. Smith2, Tara N. Jennings1, Doni McKay2, and Sarah Beldin1. (1) 3017 ALS Building, Oregon State University, Oregon State University, Dept. of Crop and Soil Science, Corvallis, OR 97331-7306, (2) USDA Forest Service, Pacific Northwest Research Station, Forestry Sciences Laboratory, 3200 SW Jefferson Way, Corvallis, OR 97331

Post-fire forest soil recovery is dependent on functioning soil biological communities. Suppression of wildfire for the last 100 years has led to large organic matter accumulations, contributing to high severity wildfires throughout the western United States. Areas of severely burned soil associated with the consumption of large down wood and stumps in direct contact with the soil are common after high severity wildfire. Excessive heating and oxidation of the soil matrix changes the top mineral layer to various shades of red. Such soils are largely void of biological activity immediately following a fire; the length of time to biological functioning is unknown. To examine the effects of burn severity on soil recovery, we measured bacterial and fungal diversity, soil respiration, infiltration, hydrophobicity, and soil nutrients from paired plots of severely burned “red soils” and less severely burned “black soils” collected from the 2003 Booth and Bear Butte Fires in central Oregon. Soil samples for preliminary testing were collected immediately after fire and prior to soil movement or soil microbial proliferation due to precipitation. In the spring of 2004 the study was expanded to include six red-black paired plots in each of five stand replacing wildfire sites; collections from all sites were made during May, July, and October of 2005-2007. Species richness of soil fungi was initially low in the severely burned red soils compared to the black soils but was more similar by year two after the fire. Severely burned soils were higher in pH than moderately burned soils; moderately burned soils were higher in carbon, nitrogen, phosphorus, and cation exchange capacity, but were also more hydrophobic. Soil respiration was not significantly different in red vs. black soils. Knowledge of post-fire soil recovery is critical to evaluating the impacts of a variety of management options essential to long-term forest management.