Low-quality carbon and lack of nutrients result in a stronger fungal than bacterial home-field advantage during the decomposition of leaf litter

Abstract

Decomposition of litter is a key biochemical process that regulates the rate and magnitude of CO2 fluxes from biosphere to atmosphere and determines soil nutrient availability. Although several studies have shown that plant litter decomposes faster in their native compared to a foreign environment, i.e. a home field advantage (HFA) for litter degradation, to date HFA has only been considered in terms of respiration or litter mass loss. The ecological success will be determined by the decomposer microorganism’s ability to transform used OM into population growth, and therefore we hypothesized that HFA for microbial growth would be more pronounced than for decomposition, by driving the feedback between community alignment and environmental resource conditions. We also expected that HFA for microbial processes would increase with lower quality litter, that the fungal role in litter decomposition would be more dominant than that of bacteria, and that HFA effects would increase with more pronounced environmental differences between sites. We designed a 2-month microcosm reciprocal transplant experiment with litter from two sites with contrasting climates (Atlantic and Sub-Mediterranean climates) and including 3 tree species (Quercus robur, Pinus sylvestris and Fagus sylvatica). We found a stronger HFA for microbial growth than for decomposition, that the nutrient content and C-quality of litter influenced the microbial HFAs, and that interactions between bacterial and fungal communities during litter decomposition modulated the HFA for litter degradation. Low litter nutrient content, strong nutrient limitations and low C-qualities all favoured fungal over bacterial decomposers, and our results suggest a dominant functional role of the fungal community and gave rise to HFA for fungal growth but that translated to only marginal implications for overall decomposition of litter.