Scaling up
In spite of an increasing effort to document and understand the ecosystem impact of microbial physiological and ecological responses to climate warming (Allisonet al. 2010; Treseder et al. 2012; Wieder et al.2013), no Earth system model that seeks to represent the role of living organisms in climate feedbacks has yet included evolutionary mechanisms of adaptation. This model is a critical first step. To predict geographic variation in evolutionary responses and effects across large geographic scales, our results highlights the need for more empirical data on variation in ecosystem (competition) traits, especially how the competitive advantage to exoenzyme producers varies with soil physical properties, and in microbial physiological traits, especially microbial mortality (see Supplementary Note 8 for further discussion of the effect of microbial traits’ temperature dependence on ecosystem-evolutionary responses). On the modeling side, three steps will be needed: accounting for soil carbon stabilization on a timescale longer than respiration (Tang & Riley 2014); for vegetation types, the associated diversity of organic substrates in litter, and corresponding diversity of microbial decomposers (Allison 2012); and for the interaction of biogeochemical cycles and associated stoichiometric constraints (Harte & Kinzig 1993; Sinsabaugh & Moorhead 1994; Schimel & Weintraub 2003; Allison 2012; Kaiser et al. 2015). As demonstrated by successful Earth-scale modeling of phytoplankton abundance and distribution in the global ocean (Followset al. 2007), future models that take these steps will trade off some of their added structural complexity with the model ‘self-parameterization’ driven by the process of adaptive trait evolution itself. As this research program unfolds, we expect projections of future climate and carbon cycle feedbacks, and their uncertainty, to be significantly impacted by microbial evolutionary adaptation, from local to global scales.