Microbiological aspects of wood chip storage in tropical environments

The microbiology of tropical wood chip storage has been examined in small experimental piles at two sites in New Guinea. Biodeterioration occurred in the forms of wood discoloration and loss of wood substance, including cellulosics; over a period of 2-4 months c. 20% per month of the chip pile by volume was seriously discoloured by microorganisms, and wood substance loss amounted to c. 1.5% per month (microscopic assessment). A range of microorganisms which produce discoloration were isolated. Decay was mainly due to soft-rotting microfungi such as Chaetomium globosum, C. thermophile, Humicola lanuginosa, Cephalosporium acremonium and Gliomastix subiculosa. Wood-rotting basidiomycetes were infrequent, although pockets of decayed (white rot) mycelial-matted chips were observed in the outer 1.5 m during dismantling of the 4-month-old pile at Vanimo. A successional trend of colonizing microorganisms was established, and profiles of the main zones of microbiological activity have been determined. The rapid rise in temperature, which is characteristic of wood chip piles after construction, had a marked influence on the microbial populations. Thermotolerant isolates included Humicola spp., Aspergillus spp., some actinomycetes, and members of the bacterial genus Bacillus. Reasonable chemical control of biodeterioration was achieved by dipping chip samples in a 1% solution of sodium pentachlorophenate. Three trichlorophenol formulations were less effective.