Although dead fungal mycelium (necromass) represents a key component of biogeochemical cycling in all terrestrial ecosystems, how different ecological factors interact to control necromass decomposition rates remains poorly understood. This study assessed how edaphic parameters, plant traits, and soil microbial community structure predicted the mass loss rates of different fungal necromasses within experimental monocultures of 12 tree species in Minnesota, USA. Necromass decay rates were most strongly driven by initial chemical composition, being significantly slower for fungal necromass with higher initial melanin content. Of the extrinsic ecological factors measured, variation in the amount of mass remaining for both low and high melanin necromass types was significantly predicted by soil bacterial richness and fungal community composition, but not by any soil microclimatic parameters or plant traits. Further, the microbial communities governing decay rates varied depending on the initial necromass chemical composition, suggesting that extrinsic and intrinsic factors interacted to propel decomposition. Finally, we also found significant positive relationships between the amount of remaining fungal necromass and soil carbon and nitrogen concentrations. Collectively, these results suggest that, after the initial chemical composition of dead fungal residues, soil microbial communities represent the main drivers of soil necromass degradation, with potentially large consequences for soil carbon sequestration and nutrient availability.
Bibliographical noteFunding Information:
We thank the editor, Marie Sauvadet, and the four anonymous reviewers for their valuable comments and suggestions, which contributed to improving the quality of the manuscript. The authors thank B. Tanner for assistance with 16S and ITS library preparation. The FAB experiment was established and maintained with support from the Cedar Creek Long Term Ecological Research program (DEB-1234162, DEB-1831944). We also acknowledge the Joint Genome Initiative “Defining the Populus Microbiome” Project, from which the M. bicolor isolate used for necromass was derived.
- Forest ecosystems
- Functional redundancy
- Microbial residues