VESICULAR-ARBUSCULAR MYCORRHIZAL SPORE POPULATIONS IN SUGAR MAPLE (ACER-SACCHARUM MARSH L) FORESTS

The numbers and types of spores of vesicular-arbuscular mycorrhizal fu ngi occurring in the top 15 cm of the soil in three maple forests in E astern Canada were investigated using traditional wet-sieving/decantin g methods. In the most acid site, at St. Hippolyte, Quebec, where the soil had been amended with base cations, after 1 year there was no eff ect on the numbers of spores present. Vesicular-arbuscular mycorrhizal spores present at St. Hippolyte consisted of Glomus rubiforme, other Glomus sp. and Acaulospora spp. Although the sporocarpic species, G. a ggregatum, G. macrocarpum and G. rubiforme occurred at St. Hippolyte, they were not found at the two less acid sites (Waterloo, Ontario and Lacolle, Quebec). Spores of Acaulospora spp. were found at all three s ites, but were most abundant at St. Hippolyte. At St. Hippolyte the to tal number of spores was much higher than at the other two sites; at W aterloo numbers were an order of magnitude lower than at St. Hippolyte . It is suggested that G. rubiforme and Acaulospora species may be ada pted to acid conditions. Seasonal patterns of spore abundance suggeste d that Acaulospora spp. may sporulate during the spring, whereas G. ru biforme may sporulate during the fall.