The interaction between climate and the microbial community determines litter decomposition

Background/Question/Methods

One of the major inputs available to microbial communities when plants are not growing is senesced leaf litter. The decomposition of leaf litter is controlled in by climate, litter quality, and finally the microbial community. All of these factors have the potential to interact but the importance of these interactions is often difficult to disentangle in traditional field based litter decomposition experiments. In particular the interaction between a changing climate and the response of geographically distinct microbial communities is unknown. Here I attempt to disentangle the effect of the interaction between climate and microbes by tracking the decomposition of a common leaf litter inoculated with one of three distinct microbial communities under altered climates. Specifically, litter inoculated with microbial communities (sourced from: Bonanza Creek, AK; Coweeta, NC; Luquillo, PR) was subjected to varying treatments of temperature (4 levels) and moisture (5 levels). This enabled me to elucidate potential interaction between microbial communities and climate with respect to litter decomposition.

Results/Conclusions

Litter decomposition was influenced by the interaction between temperature, moisture, and the microbial community. The effect of temperature and moisture on decomposition was generally represented by a unimodal response but this response was also mediated by the microbial community. Specifically the community sourced from Luquillo exhibited the strongest response to change in simulated climate and Bonanza Creek exhibited the weakest response. Of particular note is the observation that the community sourced from Bonanza Creek tended to exhibit greater litter decomposition in colder, drier climates compared to communities sourced from Luquillo or Coweeta. These latter two communities also exhibited a greater response to changes in moisture and temperature regimes when compared to Bonanza Creek. This may suggest that the contemporary climate of a community may influence its response to climate change. More importantly though, these results indicate that the response of processes, such as litter decomposition, to climate are not simply related to temperature and moisture but are also a property of the microbial community itself.