Microbial Resilience and Redundancy In Response To Global Change.

Predicted global changes are likely to alter rates of ecosystem processes such as decomposition. These drivers may affect decomposition directly, through changes in abiotic conditions, and indirectly through changes in plant and microbial communities. Thus, the response of microbially-driven ecosystem processes to new environmental conditions will depend in part on the sensitivity, resilience, and functional redundancy of the microbial communities.  To assess these potential effects of the microbial community, we reciprocally transplanted microbial communities and plant litter among treatment (either drought or N addition) and control plots in a southern California grassland.  We showed that bacterial and fungal abundance and composition was sensitive to the environmental changes and not resilient after at least two years. Further, the microbial communities were not functional redundant; community effects accounted for a similar change in litter decomposition as the direct effects of a drought treatment after the first year. These results show that environmental changes not only affect rates of ecosystem processes directly through abiotic change, but indirectly through microbial abundances and composition.