Knowledge of how forest management influences soil microbial community interactions is necessary for
complete understanding of forest ecology. In this study, soil microbial communities, vegetation characteristics
and soil physical and chemical properties were examined across a rectangular 4.57 36.58 m
sample grid spanning adjacent coniferous forest and clearcut areas. Based on analysis of soil extracted
phospholipid fatty acids, total microbial biomass, fungi and Gram-negative bacteria were found to be
significantly reduced in soil of the clearcut area relative to the forest. Concurrent with changes in microbial
communities, soil macroaggregate stability was reduced in the clearcut area, while no significant differences
in soil pH and organic matter content were found. Variography indicated that the range at which
spatial autocorrelation between samples was evident (patch size) was greater for all microbial groups
analyzed in the clearcut area. Overall, less spatial structure could be resolved in the forest. Variance
decomposition using principal coordinates of neighbor matrices spatial variables indicated that soil
aggregate stability and vegetation characteristics accounted for significant microbial community spatial
variation in analyses that included the entire plot. When clearcut and forest areas were analyzed separately,
different environmental variables (pH in the forest area and soil organic matter in the clearcut) were
found to account for variation in soil microbial communities, but little of this variation could be ascribed to
spatial interactions. Most microbial variation explained by different components of microbial communities
occurred at spatial scales other than those analyzed. Fungi accounted for over 50% of the variation in
bacteria of the forest area but less than 11% in the clearcut. Conversely, AMF accounted for significant
variation in clearcut area, but not forest, bacteria. These results indicate broadly disparate controls on soil
microbial community composition in the two systems. We present multiple lines of evidence pointing
toward shifts in fungi functional groups as a salient mechanism responsible for qualitative, quantitative
and spatial distribution differences in soil microbial communities.