Contribution of arbuscular mycorrhizal fungi to carbon fluxes in grassland in response to climate manipulation

A large component of soil CO2 efflux is driven by 'autotrophic' respiration; i.e. the flux of carbon occurring directly from plant roots and indirectly from closely associated microorganisms. Among the most important groups of root-associated microbes in grassland are arbuscular mycorrhizal (AM) fungi. These fungi form mutualistic symbioses with host plants and are entirely dependent on plant photosynthate for their energy. Despite this, our understanding of how AM fungi and the key carbon cycling activities they undertake respond to global climate change is poor, especially under field conditions. We will test the hypothesis that carbon flux to AM fungi will increase in response to increased temperature and but this will be dependent on water availability. We will further test whether climate manipulation increases the relative importance of AM fungal respiration to total soil CO2 efflux. The proposal capitalises on an existing large-scale transplant experiment in the Swiss Jura, in combination with an in situ 'pulse' of isotopically distinct carbon (i.e. 13C) to provide the first field-based assessment of the contribution of arbuscular mycorrhizal fungi to soil CO2 efflux in response to climate manipulation.