• arbuscular mycorrhizas;
  • plant life history strategies;
  • mine reclamation;
  • taconite

1.  Owing to the difficulty of finding terrestrial ecosystems without mycorrhizas, their influence on plant community dynamics is not easy to discern. This study utilized unreclaimed taconite mine tailings as a mycorrhiza-free ecosystem to gain insights about the influence of arbuscular mycorrhizas 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).

2.  To assess relative mycorrhizal responsiveness, Panicum and Salsola were grown in taconite tailings along an experimental phosphorus gradient with and without mycorrhizal fungal inoculum isolated from reclaimed taconite tailings. At low phosphorus concentrations, mycorrhizal inoculum enhanced the growth (height and dry mass) of Panicum, but it decreased growth at the two highest phosphorous concentrations. At no phosphorus level did mycorrhizal inoculum enhance the growth of Salsola but it decreased growth at the highest phosphorus concentrations.

3.  In field plots, mycorrhizal inoculum and organic soil amendment (compostedpapermill sludge) enhanced the growth of Panicum and decreased the growth of Salsola.

4.  In this experiment, mycorrhizal inoculum enhanced the growth of the late successional grass but, during reclamation operations, manipulating edaphic conditions to favour mycotrophy may be more cost-effective than large-scale inoculation. The results of this study suggest that mycotrophy is favoured by increasing soil organic matter and avoiding heavy fertilization.