| The influence of soil physical and chemical characteristics on soil stability has been examined on disturbed soils throughout the Lake Tahoe Basin; however, little attention has previously been given to the role of soil microorganisms in stability. The relationship between microbial community composition and soil stability was determined using rainfall simulation and microbial lipid analysis. Study sites were located on roadcuts and ski runs, and were from either granitic or volcanic parent material. Treatment plots at each location contained a combination of soil loosening and erosion control surface amendments. Phospholipid Fatty Acid Analysis (PLFA) was performed on soil samples from all treatment plots to determine total microbial biomass and the relative abundance of the following microbial groups and biomarkers: gram-negative bacteria, gram-positive bacteria, actinomycetes, fungi, arbuscular mycorrhizal (AM) fungi, and stress indicator biomarkers. The influence of treatment on microbial groups was determined, and microbial groups were related to the occurrence of runoff and rainfall parameters (steady runoff, infiltration, and erosion rates, as well as runoff sediment concentration and organic matter content).;Microbial communities differed by treatment. Compost sites generally contained the greatest relative abundance of bacteria, actinomycetes and AM fungi, and the least of non mycorrhizal fungi. Native sites contained the greatest abundance of fungi and the least abundance of AM fungi. At all locations, the occurrence of runoff was correlated with a higher relative abundance of gram-negative bacteria and a higher ratio of monounsaturated to saturated lipids. Increased infiltration on both ski runs and roadcuts was associated with an increased total microbial biomass, and on roadcuts was specifically associated with fungal biomass. Thus, this study shows that two important factors contributing to improved soil infiltration include: (1) increasing total microbial biomass on all sites, and (2) utilizing amendments that select for fungi on severely degraded soils (roadcuts). These relationships can guide experimental work to further evaluate how microbes interact with substrate type and other soil treatments to improve infiltration. |
