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.