Wood decay in living trees in eastern Amazonia, Brazil.

摘要

Tree stem hollows and rotten cores result from the gradual decomposition of the central woody column (heartwood) by a diverse range of organisms, mostly fungi. From both ecological and economic perspectives, the decision whether or not to harvest hollow and heart-rotted trees has substantial consequences. Retaining hollow trees in forests managed for timber, for instance, helps conserve species that use tree hollows as nesting sites. In contrast, felled hollow trees are then abandoned in the forest, which reduces profits to loggers, unnecessarily increases carbon emissions, and increases forest flammability.;Using data from inventoried stands in a naturally regenerated tropical forest managed for timber in the eastern Amazon, I investigated how the characteristics of economically important timber tree species influenced their susceptibility to heartwood decay. Tree species with higher wood specific gravities were more prone to have heartwood cavities made evident by the presence of open holes on the exterior of the trunk. Additionally, the proportion of trees with such stem cavities decreased with tree diameter. In contrast, for trees with no external openings in which hollows and rotten cores were only detected after felling there was a positive relationship between a tree’s size and its likelihood of being hollow.;I evaluated the diversity of wood decay fungi in my study site by comparing the communities of fungi with reproductive bodies emerging from coarse woody debris in an intact and a logged forest stand before logging and through a 10-month period after logging. Although no difference in fungal species richness was observed between sites, changes in the composition of fungal communities through time indicated that rare species were negatively affected by logging while there was no evident effect on fungal species that are mostly tree pathogens.;Finally, I sampled heartwood tissues from recently felled trees of five timber species to explore the diversity of fungi and termites that could actively degrade them, and evaluate tree characteristics that influenced their susceptibility to pathogen invasion. Large trees with smaller heartwood vessel sizes and higher ray and vessel density tended to have larger stem hollows. Fungal specie considered saprophytes and Coptotermes testaceus, a subterranean termite species, were frequently found in stem hollows. The presence of termite nests in heartwood varied among species and increased with wood density, but was not affected by fungal species richness.