Interactions between native prairie grasses and indigenous arbuscular mycorrhizal fungi: implications for reclamation of taconite iron ore tailing

Abstract

summaryIn a glasshouse experiment using coarse taconite iron ore tailing as the substrate, we examined interactions between the warm‐season grasses Andropogon gerardii (big bluestem) and Schizachyrium scoparium (little bluestem), and the cool‐season grass Elymus canadensis (Canada wild rye), and indigenous arbuscular mycorrhizal (AM) fungi from an adjacent fine tailing basin. Shoot dry mass (DM), P uptake, shoot P concentration, root DM, root length, spore density, percentage root length colonized, and length of external AM fungal hyphae were measured over a gradient of phosphate availability. Andropogon gerardii was highly dependent and responsive to inoculation at low P, whereas inoculation had no significant effect on the growth of 5. scoparium. Root DM and root lengths of both warm‐season grasses were unaffected by mycorrhizal inoculation. Elymus canadensis was responsive only at the lowest P level and not dependent on mycorrhizas; in fact, shoot DM, P uptake, root DM and root lengths were all greater in control than inoculated plants at moderate P levels. Despite a growth suppression, colonized root lengths for E. canadensis were approximately five times longer than warm‐season grasses at low P levels, making it suitable as an early succession species for increasing mycorrhizal inoculum potential and thus enhancing the successful reclamation of coarse tailing deposits by more persistent, mycorrhizal‐dependent species.