Are there edge effects on forest fungi and if so do they matter?

Fungi are vital within forest ecosystems through their mycorrhizal relationships with trees, and as the main agents of wood decomposition and thus carbon and nutrient cycling. Globally, forests are becoming increasingly fragmented, creating forest patches that are isolated, reduced in area, and exposed at edges. Edges are often ecologically distinct from the forest interior due to their exposure to the matrix habitat. This exposure can result in altered microclimatic conditions and flows of biotic and abiotic materials such as spores or inorganic nitrogen, respectively.Although fungi are known to be affected by microclimate and nitrogen deposition, knowledge of forest edge effects on fungi is extremely limited; however, a consideration of the factors known to regulate fungal activity in combination with known biotic and abiotic edge effects implies that forest edges are likely to strongly influence fungi. These include responses of fungi to the altered microclimate and nitrogen levels at forest edges, at both the individual and community level; interactions with plants and animals that have been influenced by edges; above–belowground feedback between mycorrhizal fungi and host trees. The small body of existing research focuses on fruit body presence and distribution; fungal biomass and community composition in soil have been touched upon. Positive, negative and neutral edge responses have been found, the majority of studies finding a significant effect on some of the parameters measured. Generally, abundance of fruit bodies and biomass in the soil is lower at the forest edge.Understanding how fungi respond to edges is essential to a more complete knowledge of carbon and nitrogen cycling in forest edges, influence of mycorrhizal species on vegetation, and conservation of rare fungi. As edges become increasingly dominant landscape features it is vital to investigate processes within them, to understand ecosystem function at a landscape scale.

► As forest fragmentation increases globally edge effects on remaining forest become important.
► Edge effects on forest fungi as decomposers, mycorrhizae and pathogens are largely unknown.
► Microclimate is altered at edges, with predicted impacts on fungal individuals and communities.
► The limited research shows positive and negative edge effects on fungal abundance and diversity.
► Fungal edge effects must be studied for a fuller understanding of forest ecosystem function.