Canadian Forest Service Publications
Effects of wildfire and harvest disturbances on forest soil bacterial communities. 2008. Smith, N.R.; Kishchuk, B.E.; Mohn, W.W. Applied and Environmental Microbiology 74(1): 216-224.
Issued by: Northern Forestry Centre
Catalog ID: 28080
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Wildfires and harvesting are important disturbances to forest ecosystems but their effects on soil microbial communities are not well characterized and have not previously been directly compared. This study was conducted at sites with similar soil, climatic and other properties in a spruce-dominated Boreal forest near Chisholm, Alberta, Canada. Soil microbial communities were assessed following four treatments: control, harvest, burn and burn plus timber salvage. Burn treatments were at sites affected by a large wildfire in May 2001, and the communities were sampled one year after the fire. Microbial biomass carbon (Cmic) decreased 18%, 74% and 53%, respectively, in the harvest, burn and burn-salvage treatments. Microbial biomass nitrogen (Nmic) decreased 25% in the harvest treatment, but increased in the burn treatments, probably because of microbial assimilation of the increased amounts of available NH4+ and NO3- due to burning. Bacterial community composition was analyzed by non-parametric ordination of molecular fingerprint data of 119 samples, from both ribosomal intergenic spacer analysis (RISA) and rRNA gene denaturing-gradient gel electrophoresis (DGGE). On the basis of multi-response permutation procedures, community composition was significantly different among all treatments, with greatest differences between the two burned versus the two un-burned treatments. Sequencing of DNA bands from RISA fingerprints revealed distinct distributions of bacterial divisions among the treatments. Gamma- and alpha-Proteobacteria were highly characteristic of the unburned treatments, while beta-Proteobacteria and members of Bacillus were highly characteristic of the burned treatments. Wildfire had distinct and more pronounced effects on the soil microbial community than did harvesting.