Vesicular-arbuscular mycorrhizae in taconite tailings. II. Effects of reclamation practices

A factorial field experiment was conducted to study the effects of two reclamation treatments (papermill sludge amendment and straw mulch) on populations of spores of mycorrhizal fungi and the percentage of plant root length colonized by mycorrhizal fungi. Unreclaimed taconite tailings were found to be essentially devoid of propagules of mycorrhizal fungi, but mycorrhizae developed rapidly following reclamation. Extremely high spore densities and levels of root colonization were observed in less than two growing seasons. Spore population densities in reclaimed taconite tailings were frequently 100-fold greater than those observed by other researchers in natural, undisturbed soils. Papermill sludge and straw mulch significantly affected sporulation of mycorrhizal fungi. Tailings amended with papermill sludge also supported significantly greater plant biomass than did unamended tailings; providing a plausible explanation for increased sporulation. In contrast, tailings treated with straw mulch contained significantly fewer spores than did unmulched tailings. Suppression of sporulation of mycorrhizal fungi may have been caused by antagonistic soil organisms introduced with the straw to the taconite tailings.