Unique Species Interactions Determine the Decomposition Activity of Fungal Communities

Microbial litter decomposition, which is largely driven by fungal communities, is a crucial process in terrestrial carbon cycling. Although the successional stages of decomposition are well-documented, the intricate interactions within these fungal communities are still poorly understood. Understanding the dynamics between different species within fungal communities is crucial for predicting decomposition rates under future environmental scenarios and will help to determine whether competition, facilitation or niche partitioning is the driving force behind interspecific interactions within fungal communities. In this microcosm experiment we investigated the impact of fungal community richness on decomposition efficiency by introducing up to six distinct fungal species to decompose maize leaf litter and cellulose. Decomposition rates, fungal biomass and respiration were measured during the experiment. The results revealed a limited positive correlation between fungal diversity and decomposition rates. All fungal communities displayed increased biomass decomposition compared to single-species treatments. However, a surprising trend emerged from the study: communities containing only four fungal species achieved the greatest litter mass degradation compared to those with six species. This suggests a potential shift in dominant interactions within the community, with mutualistic partnerships potentially outweighing competition at this particular richness level. To further understand the complexity of these interspecific relationships we fitted a diversity interaction model. The outcome of the model highlights the complex nature of fungal community dynamics and the limitations of making simple predictions. This emphasisizes the need for further research to unravel the complex interplay between fungal community dynamics and carbon mineralisation.