How can soil microbial biogeography improve our ability to predict soil responses to climate change?

Background/Question/Methods

Accurately predicting the response of soil microbial communities to climate change is critical as soil microorganisms are the dominant mediators of carbon and nutrient transformations that impact biological productivity worldwide. Despite their importance, the edaphic factors controlling microbial composition are poorly understood. The extent of phylogenetic conservatism in the response of soil microbes to climate driven perturbations in edaphic properties is unclear, as is the relative influence of a microbial community’s climate history on its ability to adapt to novel conditions.

We are focused on the response of soil microbial communities to altered precipitation and address these questions through analyses of microbial distributions across climatic gradients to identify conserved traits and through manipulative experiments in key ecosystems predicted to experience changes in rainfall frequency or magnitude. Soil microbial community and isolate responses are quantified using a range of molecular tools including microarrays, second generation sequencing and mass spectrometry.

Results/Conclusions

Factors related to precipitation explained much of the variance in soil microbial composition across climatic gradients and specific phylogenetic groups such as the Actinobacteria and Bacilli displayed conservation in their relationship with soil moisture. Bacterial taxa that are negatively correlated to soil moisture (dry adapted) contain less phylogenetic diversity and evolved from their more diverse wet-adapted ancestors suggesting that declines in rainfall could lead to decreased soil phylogenetic diversity. However, whether these physiological traits are conserved across ecosystems with vastly different climate histories is uncertain. We assessed the response of soil bacteria to decreased rainfall in desert, Mediterranean grassland and sub-tropical forest soils. The overall impact of rainfall exclusion on soil microbial communities was related to climate history but across sites, specific phylogenetic groups, such as the Actinobacteria, responded as predicted. To relate these observations to ecosystem function we are currently investigating the functional response of these communities and phylogenetic groups.