Bacteria and fungi drive decomposition, a fundamental process in the carbon cycle, yet the response of this microbial process to climate change is uncertain. To simulate climate change, we transplanted microbial communities across an elevation gradient in Southern California, USA. Precipitation increases and temperature declines with increasing elevation along the gradient. Microbial communities were inoculated onto irradiated grass litter and transplanted across five gradient sites in litter bags that restrict microbial exchange. To assess microbial functioning, we measured the activities of nine extracellular enzymes involved in litter carbon and nutrient turnover. We hypothesized that enzymatic activities would be greatest under “home-field” climate conditions; i.e. when microbial communities were inoculated into their site of origin. We compared the enzyme data to previous results on decomposition rates and microbial community composition of the transplanted litter bags.
Results/Conclusions
Although initial microbial communities differed significantly between the five gradient sites (PERMANOVA; Fungi: R2 = 0.58, P < 0.01; Bacteria: R2 = 0.61, P < 0.01), microbial functioning was not impaired following transplantation. Inoculum origin was a significant determinant of both bacterial (R2 = 0.16, P < 0.01) and fungal (R2 = 0.57, P < 0.01) community composition, but there was no evidence for home-field advantage in enzyme activity or litter decomposition. In several cases, transplanted communities showed significantly (P < 0.05) greater mass loss and enzyme activity than home-field communities. These results suggest that microbial communities along our climate gradient exhibit substantial functional flexibility. High seasonal and interannual variability in temperature and precipitation along our gradient may select for communities that can tolerate climatic changes while maintaining ecosystem functioning.