Influence of woodlot floor topography on microbial decomposer distribution

The distribution of microbial populations that decomposed sugar, cellulose and lignin‐related substrates was examined in a beech Fagus grandifolia Ehrh. and maple Acer saccharum Marsh. dominated woodlot developed on glacial till. The topography of the woodlot, characterized by rises, depressions and more extensive level areas about 1 m in diameter with a 0.5 m vertical maximum, produced a mosaic of decomposer habitats designated as high, level and low sites. In general, populations of sugar, cellulose and lignin decomposing organisms (based on ten estimates made from April to October) were two to four times higher in litter and soil samples from low sites than those from high sites. Sugar decomposing bacteria in litter were most abundant at all topographic sites. 135 × 10 6 g −1 dry litter at high sites, 396 × 10 6 g −1 at level sites and 456 × 10 6 g −1 at low sites; lignolytic fungi were least abundant, 391 × 10 2 g −1 dry litter at high sites. 700 × 10 6 g −1 at level sites and 954 × 10 2 g −1 at low sites. Numbers of microbial decomposers in the topographic sites were correlated with organic matter content. Distribution of fungal genera did not appear to be related to topographic site. Most populations examined showed two numerical peaks, one in late May or June and one in late September or October. It is suspected that these peaks were influenced by the coincident timing of favourable physical conditions and priming by soluble nutrients leached from litter.