The effect of surface mining on the infectivity of vesicular-arbuscular mycorrhizal fungi

We tested the hypothesis that soil disturbance associated with mining will reduce the infectivity of propagules of vesicular-arbuscular (VA) mycorrhizal fungi to different extents, depending on the mining operation and the environment. At each of four mine sites, the infectivity of VA mycorrhizal fungi was estimated in soil from native vegetation, disturbed topsoil and revegetated soil. Infectivity was measured using subterranean clover and Acacia species as bioassay plants. In a second experiment the effects of soil disturbance and soil storage on infectivity of VA mycorrhizal fungi were measured separately. Topsoil disturbance decreased the number of spores or the number of spore types that could be isolated from the soil, and reduced or delayed formation of VA mycorrhizas. Glasshouse treatments indicated that both disturbance and a period of storage without plant growth contributed to the loss in infectivity of propagules of VA mycorrhizal fungi. After 4-5 years of revegetation, the number of infective propagules appears to be restored to a level equivalent to that of undisturbed soils. The possibility of improving revegetation by increasing the inoculum potential of disturbed soils needs to be investigated.