Soil microbial responses to land use and climatic changes in the light of evolution
Soil microbes are important drivers of carbon and nutrient fluxes in terrestrial ecosystems through their strong contribution to organic matter decomposition and nutrient cycling. However, these ecological processes are supported by a large diversity of microbes with a wide range of life history traits. For example, fast-growing microbes (-r strategy) take up labile carbon, immobilise nutrients in their biomass and stabilise soil carbon in their necromass, while slow-growing microbes (-K strategies) decompose recalcitrant organic matter and recycle nutrients stored in the soil. Other strategies have been proposed and their classification according to functional traits is still under debate. Recent metagenomic studies have shed light on the combination of traits that characterise microbial communities depending on their environment, but species-level uncertainty remains. We propose a trait- and individual-based and spatially explicit model of microbial communities, including evolution, to explore the emergence of ecological strategies. In particular, we consider three main trade-offs linking traits: energetic expenditure of physiological processes, allocation of biomass in the cell and stoichiometry of cell components, which interact with environmental factors such as organic matter quality, availability, stoichiometry and stress. Our model allows us to understand how adaptation to conditions at the local scale shapes the functioning of the whole ecosystem.