Effects of recreational impacts on soil microbial communities

The functional diversity of soil microbial communities in heavily impacted subalpine campsites and adjacent undisturbed areas was compared using the Biolog method of carbon utilization profiles. Principal components analysis of patterns and level of microbial activity indicate that microbial communities differentiate in response to disturbance in the top 6 cm of soil, while below 6 cm there were no recognizable differences between disturbed and undisturbed soil communities. Analysis of the factors that differentiate the upper microbial communities between disturbed and undisturbed sites revealed that the percent of total carbon sources utilized was significantly less in the disturbed (54%) than in undisturbed areas (95%). Carbon substrates important in the discrimination between soil communities include plant, invertebrate, and microbial derivatives that could not be metabolized by microbial communities from disturbed sites. Comparisons of total culturable actinomycetes, bacteria, and fungi reveal no difference in overall number of colony forming units (CFU) on disturbed and undisturbed sites, but a marked decrease in actinomycetes on disturbed sites. Biolog and spread-plate data combined indicate a shift in the structure and function of the microbial community in campsite soils, which may be a useful indicator of soil community disturbance.