Microbial ecology of untreated and copper–chrome–arsenic treated stakes exposed in a tropical soil. 1. The initial invaders

Abstract

A study of the microbial ecology of copper–chrome–arsenic treated and untreated Pinus radiata and Eucalyptus regnans sapwood ground stakes exposed for a total of [Formula: see text] years is currently being made. The results presented in this report cover the initial colonization period during the first 7 months of exposure. Soft rot in the outer layers of both species of untreated wood occurs after only 1 month in the ground. Treatment with CCA prevents the early attack of pine but is not as effective in the eucalypt, nor does it appear to have a significant effect upon the diversity of microorganisms which colonize the two woods. For the first 2 months Penicillia are the predominating members of the population. Trichoderma viride, Paecilomyces fumo-roseus, and Cladosporium spp. are also frequently isolated. At 4 months more active soft-rotting fungi can be isolated, e.g. Chaetomium globosum and Humicola grisea, together with Fusaria and Phycomycetes. Bacteria colonize the stakes at a very early stage, the population changing little over this initial period of the study. Actinomycetes were not isolated until the wood had been in the ground for a month or more after which their importance in the population has steadily increased. Basidiomycetes were microscopically observed in sections of the stakes but have not been isolated to date.