Development of wood decay in Parashorea malaanonan blanco (Merr.) wounded by logging
The development of wood decay in wounded commercial dipterocarp species, Parashorea malaanonan Blanco (Merr.) in conventional logging (CL) and reduced impact logging (RIL) forests was quantified and fungal isolates were characterised. The isolated basidiomycetous fungi were tested both in vitro and in vivo. All 40 samples examined (7 years post-logging) had stem defects ranging from 10-44%, and the decay volume was positively correlated to wound size. Mid-bole wounds had relatively more decay than the upper bole or the basal wounds with 40% and 45% decay in CL and RIL respectively. Five of the 36 fungal morphotypes associated with the decayed wounds showed positive results to ligninolytic and celluloytic tests. Interspecific interactions most commonly resulted in eventual overgrowth of these basidiomycetes by the mitosporic fungi. Colony expansion was influenced by the presence of competitors when co-inoculations were used with and without spatial separation. Clear DNA profiles of the basidiomycete isolates were obtained via microsatellite primers GCA and CCA and distinguished them from known isolates supplied by the Forest Research Institute of Malaysia (FRIM). Wood (block) type and fungi influenced the extent of decay; Parashorea sp. (P. malaanonan - 68% and P. tomentella - 73%) were more vulnerable than the Hevea brasiliensis (58% weight loss after 48 weeks). Heartwood-sapwood differences were significant, and micro-morphological observation under SEM showed wood degradation of the white rot type; these implied the importance of physico-chemical factors of substrates for fungal decay. Field inoculation demonstrated that fast growing trees developed more defects that slow growing trees (>12 months). This thesis has demonstrated that access to a woody substrate, the ecological behaviour of fungi and intrinsic characteristics of the host are very important in the development of decay in trees.