Fungal succession and decomposition of Pinus densiflora snags

Fungal decomposition of coarse woody debris has an essential role in the biodiversity and carbon and nutrient dynamics in forest ecosystems. However, our knowledge of the effects of fungal species and within-stem diversity on wood decay is limited. In this paper, I described the process of wood decay and fungal succession of pine (Pinus densiflora) snags using chronosequence method. The results showed that the decay process differed between sapwood and heartwood. Sapwood decayed faster than heartwood, despite their initial densities being the same. Sapwood decay occurred in two phases. The first phase involved a typical white-rot process wherein acid-unhydrolysable residue (lignin) and holocellulose decayed simultaneously. White-rot species, such as Trichaptum abietinum and Phanerochaete sordida, were the dominant fungi and were likely the functional decomposers in this phase. The second phase involved selective decomposition of holocellulose. The dominant fungi in this phase included soft-rot species, such as Trichoderma spp., that can decompose holocellulose in wood that was previously delignified by white-rot species. In contrast to sapwood, heartwood experienced less loss of wood density and no clear change in lignocellulose composition, even in later stages of decay. Dominant fungi in heartwood included the latent inhabitants of living pine trees, such as Ascocoryne cylichnium, which is known to reduce colonization and wood decay by strong decomposers. These results suggest that, in addition to decay-resistant chemicals present in heartwood, the differences in the fungal communities present in heartwood and sapwood were responsible for the differences in their decay rates.