Knowns and unknowns of the soil fungal necrobiome

Dead microbial cells, commonly referred to as necromass, are increasingly recognized as an important source of both persistent carbon as well as nutrient availability in soils. Studies of the microbial communities associated with decomposing fungal necromass have accumulated rapidly in recent years across a range of different terrestrial ecosystems. Here we identify the primary ecological patterns regarding the structure and dynamics of the fungal necrobiome as well as highlight new research frontiers that will likely be key to gaining a full understanding of fungal necrobiome composition and its associated role in soil biogeochemical cycling. Because many members of the fungal necrobiome are culturable, combining laboratory functional assays with field-based surveys and experiments will allow ongoing studies of the fungal necrobiome to move from largely descriptive to increasingly predictive. Fungal necromass is a dominant component of the dead microbial cells associated with persistent carbon in soils as well as a significant source of nutrient availability for plant and microbial uptake.Recent molecular-based analyses of decomposing fungal necromass in a range of ecosystems have found a selective but dynamic microbial community that is codominated by bacteria and fungi.Despite considerable taxonomic and functional variation in the fungal necrobiome over time, there appears to be a consistent set of bacteria and fungi encountered on decomposing fungal necromass across geographically and vegetatively diverse ecosystems.The most abundant microbial taxa found in molecular surveys of decomposing fungal necromass are culturable, so both laboratory assays and manipulative ecological experiments should be conducted to better understand the processes underlying fungal necrobiome assembly.