Since fungi and bacteria are the dominant decomposers in soil, their distinct physiologies are likely to differentially influence rates of ecosystem carbon (C) and nitrogen (N) cycling. We used meta-analysis and an enzyme-driven biogeochemical model to explore the drivers and biogeochemical consequences of changes in the fungal-to-bacterial ratio (F: B). In our meta-analysis data set, F: B increased with soil C: N ratio (R2 = 0.224, P < 0.001), a relationship predicted by our model. We found that differences in biomass turnover rates influenced F: B under conditions of C limitation, while differences in biomass stoichiometry set the upper bounds on F: B once a nutrient limitation threshold was reached. Ecological interactions between the two groups shifted along a gradient of resource stoichiometry. At intermediate substrate C: N, fungal N mineralisation fuelled bacterial growth, increasing total microbial biomass and decreasing net N mineralisation. Therefore, we conclude that differences in bacterial and fungal physiology may have large consequences for ecosystem-scale C and N cycling.
- Biogeochemical model
- N mineralisation