Functional diversity of ligninolytic fungi associated with leaf litter decomposition

Fungi play central roles in leaf litter decomposition as they are capable of actively decomposing lignin and other recalcitrant components in leaf litter that impact the decomposition in terrestrial ecosystems. Quantitative evaluation is lacking, however, regarding the ability of diverse fungi to decompose leaf litter and the variability of ligninolytic activity among fungal taxa. In this comprehensive synthesis, I summarize the data of 1,232 individual pure culture tests conducted under standardized protocols to examine the functional diversity of fungi associated with leaf litter decomposition, with special emphasis on the ligninolytic activity. Fungal strains tested included 218 species in 69 families of Basidiomycota, Ascomycota, and Mucoromycotina that were derived from tropical and temperate forests to polar tundra. Fungal strains were inoculated adjacent to sterilized leaves and other substrata and incubated in the laboratory in order (a) to examine their functional potentialities in terms of the ability to cause mass loss of leaves and decompose recalcitrant components and (b) to explore the effect of litter quality and various environmental factors. The results of these tests revealed that ligninolytic abilities were specifically detected in fungal strains in such families as Mycenaceae and Marasmiaceae in Basidiomycota, and Rhytismataceae and Xylariaceae in Ascomycota. The ligninolytic activity varied among fungal taxa and with the quality and type of substrata, incubation temperature, and external supply of nutrients. This review provides integrative accounts of the functional diversity of ligninolytic fungi associated with leaf litter decomposition and enhances our understanding of the roles of fungal diversity in decomposition processes.