Vegetation and soil microbial communities three years after wildfire in spruce-fir forests of northwestern Wyoming

Graduation date: 2005The Normalized Burn Ratio and Composite Burn Index were used to classify burn severity in three sites that experienced lightning-ignited wildfire in the year 2000. The effect of burn severity (unburned, low, moderate, and high severity classes) was\ud investigated on vegetation and soil microbial community composition. Vegetation\ud communities showed a strong response to burn severity, with distinct communities associated with each burn severity class. Indicator Species Analysis was used to\ud identify plant species associated with each burn severity class; one interesting result\ud from ISA was that trembling aspen (Populus tremuloides) seedlings emerged as an\ud indicator of the moderate severity class. Species richness and tree seedling density\ud differed among burn severity classes. Soil microbial communities were analyzed using Phospholipid Fatty Acid analysis and showed moderate variation among burn severity classes and study sites. Total soil carbon and nitrogen did not differ with burn\ud severity. The C:N ratio, total soil S, and soil pH differed significantly among burn\ud severity classes. While the effect of burn severity is pronounced upon vegetation three\ud years post-fire, effects on soil microbial communities are less evident. This could be\ud attributed to the insulating properties of soils, the time elapsed after fire, or it could be an artifact of the sampling technique