Re-establishment of VA mycorrhizas following severe disturbance: comparative patch dynamics of a shrub desert and a subalpine volcano

Although current models of the roles of VA mycorrhizas in succession describe the fungal effects on the plant, they ignore the immigration patterns of the fungi. It is suggested here that the vectors of spore immigration (animals and wind) determine the pattern of re-invasion with respect to the patches of vegetation establishing on a disturbed site. The environment dictates the dominant vector. If invasion is facilitated by animals (locomotion), such as at Mount St Helens, they inoculate patches of plants, not individuals, and the patches change faster than immigration rates. Thus, the island biogeography equilibrium model is not applicable to describe VA mycorrhizal fungal establishment. If invasion is by wind (mass flow), such as in a cold desert system, inoculum is rapidly distributed across a site and VA mycorrhizal fungal richness and density rapidly equilibrates with its resource, a single shrub. By applying these models, a priori prediction of establishment following catastrophic disturbance might be possible, as opposed to mere description.