Effects of forest soil acidification on ectomycorrhizal and vesicular—arbuscular mycorrhizal development

Abstract

Seedlings of Pinus contorta Dougl. and Phleum pratense L. were grown in the greenhouse in forest floor (F/H horizons) and mineral soil from a P. contorla stand which had been acidified (pH 1.6 5.2) with S° dust over a 5‐year period. Although S° dust was the primary treatment it was assumed that acidification accounted for the major effects on the plants and mycorrhizas. Pinus contorla failed to grow below pH 2.8 and ectomycorrhizas were absent below pH 3.3. Pheleum pratense ceased growth at pH 3.3 and no vesicular‐arbuscular (VA) mycorrhizas were formd below pH 4.0. There did not appear to be any relationship between the relative abundance of coarse and fine VA mycorrhizal endophytes and soil acidity. Cenococcum geophilum L. was a common ectomycorrhizal associate of pine seedlings grown in the F/H soil, and E‐strain fungi (Complexipes), Mycelium radicis atrovirens Melin, Tomentella sp. and Suillus sp. were all more common in the mineral soi than in the F/H soil. Piloderma bicolor (Peck) Julich was observed to occur in large, discrete patches in the undisturbed natural stand but did not form ectomycorrhizas in the greenhouse. Both P. pratense and P. contorla were capable of good growth in extremely acid soils in a non‐mycorrhizal state. Copyright © 1989, Wiley Blackwell. All rights reserved