Vesicular‐arbuscular Mycorrhiza in Natural Vegetation Systems

S ummary The intensity of vesicular‐arbuscular mycorrhizal infection was assessed in the major vegetation types of east‐central England. All of the most important species of grassland, scrub and woodland were mycorrhizal and each individual of any species normally carried a heavy VA infection. Members of the Gramineae were particularly heavily infected. In limestone grassland, infection extended to members of the Cyperaceae and Juncaceae. Infection levels were high throughout the year, the highest levels occurring in the most nutrient‐stressed situations. Mycorrhiza develops soon after germination, often while seedlings are still in the cotyledon stage. Since numbers of viable Glomus type spores are low, infection is thought to arise from root to root contact rather than from spores. The Ecological implications of the widespread infection are discussed.