Role of fungal communities in carbon and nutrient cycling in forest soils under elevated atmospheric CO2 concentrations

Soil fungi play a number of influential roles in forest ecosystems. They can be broadly categorised as saprotrophs, breaking down organic matter; symbiotrophs, associating with a host organism; and pathogens, causing disease. Given considerable functional diversity within as well as between these groups, any change in fungal community composition could have important repercussions for ecosystem functioning. This project will use the Birmingham Institute of Forest Research Free Air Carbon dioxide Enrichment facility (BIFoR FACE), a large-scale experiment in Staffordshire (UK) in which patches of mature oak woodland are subjected to elevated [CO2] (+150 ppm above ambient), to explore how soil fungal communities might be affected by rising CO2 levels and what the implications of this could be for carbon and nitrogen cycling in particular. CO2 enrichment is generally expected to enhance the growth of trees, but this growth enhancement may be short-lived if soil nutrients such as nitrogen become limiting. Furthermore, increased tree growth may not necessarily increase carbon storage at the ecosystem level if it is underpinned by heightened decomposition in order to maintain the supply of nutrients. Soil fungi are central to both of these questions as some ectomycorrhizal fungi have the capacity to "mine" nitrogen from inaccessible organic pools and transfer it to their plant hosts, potentially averting nitrogen limitation, but fungal decomposition on the other hand could drive carbon losses from the soil. ITS metabarcoding will be used to characterise soil fungal communities under elevated and ambient [CO2] at BIFoR FACE, to investigate whether they are affected by CO2 enrichment. Potential implications for carbon and nitrogen cycling will then be explored by looking at correlations between soil fungal community composition and soil chemistry parameters, and metabolomics will be employed to look more directly at soil fungal functioning.