A COMPARISON OF SPATIAL HETEROGENEITY OF VESICULAR-ARBUSCULAR MYCORRHIZAL FUNGI IN 2 MAPLE FOREST SOILS

The variations in the numbers of propagules and in the colonization ra tes of vesicular-arbuscular mycorrhizal fungi in soils of two sugar ma ple forests, one near Waterloo in southern Ontario, the other near Lac olle in southern Quebec, were investigated. Both forests comprised sim ilar plant communities, and in each case the most numerous mycorrhizal spores were identified as those of Glomus macrocarpum, Glomus geospor um, and Acaulospora foveata. In both forests, root colonization and le ngth of hyphae in soil peaked in spring and again in autumn, and spore densities were highest in autumn and gradually decreased during the r est of the year. Mean percent root colonization at Lacolle was twice a s high as at Waterloo, and mean spore densities were almost 10 times h igher. In contrast. average total length of hyphae in the soil was app roximately 10 times higher at Waterloo than at Lacolle. Sporulation by G. macrocarpum was positively correlated with soil organic matter con tent, and sporulation by A. foveata was negatively correlated with inc reasing pH. Root colonization was not correlated with spore densities but was positively correlated with the total length of hyphae in the s oil. Relationships among root colonization, production of external hyp hae, and spore abundance in natural ecosystems are discussed.