Ecological impacts of fungal wood decay types: A review of current knowledge and future research directions

Abstract

I summarize current knowledge about the ecosystem functions of wood decomposition in forests with a particular focus on the effects of fungal wood decay types (traditionally categorized into white-, brown-, and soft-rot) on the community composition of saproxylic organisms, forest tree regeneration, and carbon sequestration. Deadwoods of different decay types show markedly different physicochemical and biological properties. High carbohydrate availability in white-rotted wood promotes the activities of nitrogen-fixing bacteria; thus white-rotted wood is a good dietary source for many wood-eating invertebrates. In contrast, brownrotted wood is unattractive to saproxylic communities due to the high recalcitrance of accumulated lignin, low nutrient content, and low pH. Nevertheless, some species have adapted to these conditions and form distinctive communities on brown-rotted wood. Tree seedlings that are associated with brown-rotted wood are symbiotic with arbuscular and ericoid mycorrhizal fungal species, but not ectomycorrhizal species. Thus, the diversity of fungal communities associated with a variety of wood decay types produces habitat diversity for saproxylic communities and promotes biodiversity in forest ecosystems. Wood decay type also affects carbon sequestration in forests as brown-rotted wood might be more instrumental in soil organic matter accumulation than white-rotted wood. An important aspect of wood decay type is that the wood decay activities of fungi can have indirect long-lasting cascading impacts on forest biodiversity by altering the physicochemical properties of deadwood. Including the effects of wood decay type in ecological models is thus important for predicting the long-term dynamics of biodiversity, vegetation, and carbon cycling in forest ecosystems.carbon cycling, deadwood, ecological networks, forest biodiversity, wood decay fungi Yu Fukasawa is the recipient of the 23rd Miyadi Award of the Ecological Society of Japan.

Risk assessment of fungal materials

“…Saprotrophic fungi that degrade wood are classified as white-, brown- and soft-rot fungi. White-rot fungi (mainly Basidiomycota) degrade cellulose, hemicellulose and lignin, whereas brown-rot (Basidiomycota) degrade cellulose and hemicellulose, but do not depolymerize lignin [ 30 , 32 , 38 , 39 ]. Soft-rot is dominated by soil-inhabiting Ascomycota that break down cellulose and hemicellulose and lignin as well, albeit at a much lower rate [ 32 ].…”

Coarse woody debris density and carbon concentration by decay classes in mixed montane wet tropical forests

“…Mechanisms underlying variation in patterns of dead wood C change through decomposition are largely related to decay type (Fukasawa, 2021; Martin et al, 2021). Lignin has a considerably higher C concentration than cellulose and hemicellulose.…”

“…Regionally, identifying the role of invertebrates in tropical dead wood decomposition is essential to better predict the wood vs soil and void proportion in CWD of different decay classes (Shorohova et al, 2021). Distinguishing wood decay type is important for predicting density and other physiochemical characteristics of wood (Fukasawa, 2021). Wood decay types are determined by wood‐decaying fungi and are traditionally categorized into three types—white‐rot, brown‐rot, and soft‐rot—based on their species‐specific ability to decompose lignin, cellulose, and hemicellulose (Eaton & Hale, 1993).…”

Sheltering Role of Well-Decayed Conifer Logs for Forest Floor Fungi in Long-Term Polluted Boreal Forests

“…In natural unmanaged boreal forests, coarse woody debris (CWD) accounts for substantially more than 50% of forest floor detritus mass (Grier and Logan, 1977). It is essential for highly diverse saproxylic biota (Lassauce et al, 2011) and provides food, shelter, and opportunities for reproduction among other ecological guilds (Harmon et al, 1986;Tedersoo et al, 2003Tedersoo et al, , 2008Koch et al, 2010;Fukasawa, 2012Fukasawa, , 2016Fukasawa, , 2021Stokland et al, 2012;Dittrich et al, 2014;Checko et al, 2015).…”