Effects of metal phytoextraction practices on the indigenous community of arbuscular mycorrhizal fungi at a metal-contaminated landfill

Phytoextraction involves use of plants to remove toxic metals from soil. We examined the effects of phyto-extraction practices with three plant specie s (Silene vulgaris, Thlaspi caerulescens, and Zea mays) and a factorial var iation of soil amendments (either an ammonium or nitrate source of nitrogen and the presence or absence of an elemental sulfur supplement) on arbuscul ar mycorrhizal (AM) fungi (Glomales, Zygomycetes) at a moderately metal-con taminated landfill located in St. Paul, Minn, Specifically, we tested wheth er the applied treatments affected the density of glomalean spores and AM r oot colonization in maize, Glomalean fungi from the landfill were grouped i nto two morphotypes characterized by either light-colored spores (LCS) or d ark-colored spores (DCS), Dominant species of the LCS morphotype were Glomu s mosseae and an unidentified Glomus sp., whereas the DCS morphotype was do minated by Glomus constrictum. The density of spores of the LCS morphotype from the phytoremediated area was lower than the density of these spores in the untreated landfill soil. Within the experimental area, spore density o f the LCS morphotype in the rhizosphere of mycorrhizal maize was significan tly higher than in rhizospheres of nonmycorrhizal S. vulgaris or T. caerule scens, Sulfur supplement increased vesicular root colonization in maize and exerted a negative effect on spore density in maize rhizosphere. We conclu de that phytoextraction practices, e.g., the choice of plant species and so il amendments, may have a great impact on the quantity and species composit ion of glomalean propagules as well as on mycorrhiza functioning during lon g-term metal-remediation treatments.