If the disturbance event can be anticipated, as in the case of mining or logging, it may be possible to minimize the adverse effects to mycorrhizal communities through topsoil protection. In work undertaken by Miller et al. (1998), EM fungi persisted on dying roots following fires for over a year after the trees were dead: new seedling roots could tap this resource if it remains intact. Since most mycorrhizal fungi are present in the upper soil profile, topsoil serves as a reservoir of fungal inoculum, as well as a hospitable environment for invading propagules. Therefore, the careful management of topsoil should alleviate the need for intense inoculation efforts after disturbance. For example, when possible, disturbance to soil should be minimized by limiting or eliminating activities that exacerbate the level of impact (Allen et al. 1999). This allows mycorrhizae associated with plants and organic matter to stabilize soil and reduce erosion. It also protects intact hyphal networks that can rapidly form mycorrhizae on uncolonized roots of neighboring plants (Francis et al. 1986; Smith and Read 1997). In situations where land is to be eventually disturbed, the most effective means to preserve mycorrhizae may include salvaging the topsoil before disturbance and respreading it afterwards or transferring it away from the site to another disturbed area (Allen et al. 1999). Top-soiling can be a significant source of microbes, plant propagules, and organic matter (Allen and Allen 1980); however, critical to the benefits of top-soiling is the length of time, the soil spends without plant cover necessary to sustain symbiotic relationships. Soil may be stockpiled for several years, during which time organic matter (Schwenke et al. 2000), chemical composition (Kundu and Ghose 1997), and infectivity of mycorrhizal propagules can change greatly (Miller et al. 1985). Even after soil reapplication, slow or poor seedling recruitment may further hinder mycorrhizal establishment. Planting a dense cover crop of the appropriate plants on soil stockpiles could enhance the survival and subsequent establishment of mycorrhizal fungi on restoration sites.
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