Biotic and climatic factors affecting the colonisation of wood-invading fungi

Abstract

Interactions between wood-inhabiting Mcromycetes and between this group and other colonising organisms, including Basidiomycetes and bacteria were investigated. The results indicated that the Micromycetes produced substances which inhibited the growth of bacteria and the germination of the spores of other Micromycetes.
The role of superior enzyme production in fungal colonisation was investigated and it has been established that the competitive ability of a fungus in terms of enzyme production may be assessed more readily by its Cellulolysis Adequacy Index (C.A.I.) rather than by growth rate measurement, or by enzyme production assays alone.
The results of interaction experiments conducted under conditions which simulated the changing nutritional status of newly felled wood, showed that inhibition of growth is likely to be due to the production of toxic secondary metabolites when soluble sugars are plentiful. However,when cellulose was the only carbon source available, the resUlts indicated that growth rates became the major competitive criterion.
Interactions between Micromycetes and a Basidiomycetes were investigated at a range of carbon to nitrogen ratios, representative of thoe likely to occur on the outer millimetres of dried wood. It was found that the Basidiomycete was inhibited by the Micromycetes at the lower C/N ratios of 50:1 and 100:1, and that this inAibition is most likely to be caused by the production of toxic secondary metabolites by the Micromycetes.
The importance of fungal propagule availability and the role of propagule vectors in the colonisation and succession of in-service .ioinery was investigated. It is considered that the availability of fungal propagules in air is the main source of fungal infection.
However, the diversity of the fungal flora found in air was not reflected in the fungal isolations taken from the surface, or at
depth within timber joinery. It has been demonstrated also that the painting and siting of timber joinery affects its moisture
conlent, which is the major factor influencing colonisation by microfungi. These results indicated that the competitive interactions between fungi are much more important in their colonisation and succession onto in-service joinery than the mere availability of fungal propagules.