Recovery of soil microbial communities after disturbance: Fire and surface mining

Soil microbial communities were examined in two chronosequences of reclaimed surface mine soil and in a chronosequence of previously burned sites to determine how these communities recover through time after disturbance. Phospholipid fatty acid (PLFA) methods for microbial community analysis were used to quantify microbial biomass, diversity, and abundance of specific microbial groups (gram positive bacteria, gram negative bacteria, fungi, arbuscular mycorrhizal fungi, and actinomycetes). Multivariate analysis of variance (MANOVA) and discriminant analysis (DA) were used to compare soil microbial communities and site environmental factors. The soil microbial community in sagebrush-grassland ecosystems disturbed by fire appeared to recover to similar levels of biomass and diversity as in unburned soil within 3 to 7 years. In the surface mine reclamation sites, microbial recovery was seen in 5 to 10 years after reclamation in sites dominated by sagebrush and within 14 years after reclamation in the sites dominated by cool season grasses. Plant community composition was found to have influences in soil microbial recovery. Microbial communities in soil under crested wheatgrass (Agropyron cristatum) recovered to greater biomass than did the communities associated with other plant species. Soil fungi appeared to be the most adversely affected by soil disturbance associated with surface mining than the other microbial groups examined, and they were also slow to recover after the initiation of reclamation. A general trend of recovery towards the undisturbed condition with reclamation age was found for all microbial groups after disturbance. Our data on microbial community recovery from fire and impacts of surface mining suggests that soil microbial communities are highly resilient to disturbances.