Respiratory activity of fungal associations in zones of heart rot and stain in sugar maple

Abstract

Some of the progressive changes in decay in maple trees were studied by comparing total activity of the decay community (as measured by carbon dioxide output of excised samples), water content, pH, and predominant microorganisms (as shown by isolation on malt agar) in zones selected across the pocket of decay.Four trees from which Fomes igniarius were isolated gave consistent results with alkaline pH, high moisture content, and a predominance of imperfect fungi in the zones of incipient decay. Surprisingly, these zones showed the highest rates of carbon dioxide output, though they were only slightly higher than those of the transition zones. The center, severely decayed, parts of the trees were slightly acid, appreciably drier, and contained F. igniarius in abundance. They showed only about half the rate of carbon dioxide production of the outer zones. A section of rot caused by Polyporus glomeratus corresponded in most respects to those with F. igniarius.In samples of two regions from which no basidiomycete decay fungus was isolated, the pattern was completely different. In these the pH was consistently alkaline all across the pocket, exceeding pH 9 in one central area, and was highest in the central zone. The moisture content of these two trees was very high, being highest in the central zones, and the carbon dioxide production was much higher than that of the F. igniarius decays.