Functional and ecological consequences of saprotrophic fungus-grazer interactions

Saprotrophic fungi are key regulators of nutrient cycling in terrestrial ecosystems. They are the primary agents of plant litter decomposition and their hyphal networks, which grow throughout the soil-litter interface, represent highly dynamic channels through which nutrients are readily distributed. By ingesting hyphae and dispersing spores, soil invertebrates, including Arthropoda, Oligochaetae and Nematoda, influence fungal-mediated nutrient distribution within soil. Fungal physiological responses to grazing include changes to hydrolytic enzyme production and respiration rates. These directly affect nutrient mineralisation and the flux of CO2 between terrestrial and atmospheric pools. Preferential grazing may also exert selective pressures on saprotrophic communities, driving shifts in fungal succession and community composition. These functional and ecological consequences of grazing are intrinsically linked, and influenced by invertebrate grazing intensity. High-intensity grazing often reduces fungal growth and activity, whereas low-intensity grazing can have stimulatory effects. Grazing intensity is directly related to invertebrate abundance, and varies dramatically between species and functional groups. Invertebrate diversity and community composition, therefore, represent key factors determining the functioning of saprotrophic fungal communities and the services they provide. The ISME Journal (2012) 6, 1992-2001; doi:10.1038/ismej.2012.53; published online 21 June 2012