Responses of Salsola kali and Panicum virgatum to mycorrhizal fungi, phosphorus and soil organic matter: implications for reclamation.
Unreclaimed taconite mine tailings in Arizona, USA, were used as a mycorrhiza-free ecosystem to gain insights about the influence of vesicular-arbuscular mycorrhizas (VAM) and soil organic matter on the growth of Salsola kali (an early successional colonist of taconite tailings) and Panicum virgatum (a late successional grass planted during reclamation). To assess relative mycorrhizal responsiveness, P. virgatum and S. kali were grown in taconite tailings along an experimental phosphorus gradient with and without VAM inoculum isolated from reclaimed taconite tailings. At low phosphorus concentrations, VAM inoculation of roots enhanced the growth (height and dry mass) of P. virgatum, but it decreased growth at the two highest phosphorus concentrations. At no phosphorus level did VAM inoculum enhance the growth of S. kali but it decreased growth at the highest phosphorus concentrations. In field plots, mycorrhizal inoculum and organic soil amendment (composted paper mill sludge) enhanced the growth of P. virgatum and decreased the growth of S. kali. Large-scale inoculation of reclamation sites, increasing soil organic matter and avoidance of high rates of fertilizers was recommended.