PARENT SESSION
Poster Session # 11: Disturbance Ecology.

Tuesday, August 5 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Prescribed fire effects on the soil biogeochemistry of mixed-conifer forests in Sequoia National Park, California.

Hamman, Sarah ^*,1, Burke, Ingrid ¹, ¹ Colorado State University, Ft. Collins, CO

ABSTRACT- Prescribed burning of forests may have significant effects on water and nutrient availability, and understanding these will aid in determining the most efficient and practical restoration activities. We collected data on soil moisture, N mineralization and soil respiration during the summer of 2002 in control and burned sites of an old-growth mixed-conifer forest of Sequoia National Park, California. We measured nitrogen mineralization using the soil core incubation method and the resin strip method, and measured soil respiration using a PP Systems soil respirometer. Soil moisture decreased by 2.9% with prescribed burning due to the increased soil temperature and possible formation of a water-repellant layer. Soil respiration rate decreased by 0.44g CO₂/m²/hr, most likely from the lack of autrotrophic contribution to total soil respiration. There was a significant increase in nitrogen mineralization rate with prescribed burning (0.83 g N/resin strip/day) that was likely due to a shift in microbial activity from an increase in labile SOM (carbon source), an increase in soil temperature and the decreased plant nutrient uptake. All results were significant at p<0.0001. The information gathered from this project will be used, along with data collected for the Fire and Fire-Surrogate Study, to determine overall effects of prescribed burning on the physical and chemical properties of soils in the mixed-conifer zone of the Sierra Nevada.

Key words: prescribed fire, nitrogen mineralization rate, soil respiration rate