Soil quality assessments are essential for determining impacts on belowground microbial community
structure and function. We evaluated the suitability of active carbon (C), a rapid field test,
as an indicator of soil biological quality in five paired forest stands (clear cut harvested 40 years
prior and unharvested) growing on volcanic ash-cap soils in northern Idaho. Active C was compared
with several traditional measures of soil microbial properties (microbial biomass, respiration,
fungal hyphal biomass, bacterial number and biomass and PLFA community structure). Despite
the significant differences in forest vegetation between paired stands, no differences in active
C and only a few significant differences in microbial properties were detected. Total bacteria
(microscope counts) and PLFA signatures (gram positive bacteria, gram negative bacteria, actinomycetes)
were significantly higher in the managed stands. Our results indicate that either mineral
soil biological properties in managed stands were relatively unaffected at the time of harvest
or some biological recovery occurred 40 years later. Additionally, volcanic ash-cap soils in moist
ecosystems could be highly resilient to the impacts of harvest operations and therefore few significant
biological changes could be detected.