Relative effectiveness of ten species of arbuscular mycorrhizal fungi native to a revegetated coal strip mine site was tested on red clover against a non-mycorrhizal control and against inocula of two commercial isolates. Most (70%) of the isolated species in a native fungal community were as effective at promoting growth as commercial isolates. The net benefit of native colonizing fungi likely was positive, since the majority of the fungi colonizing two-year-old apple and grape in the field also were effective symbionts. The relationship between colonization and sporulation was compared among one Acaulospora , two Glomus, one Gigaspora, and one Scutellospora species on red clover. Threshold levels of colonization at which sporulation was initiated ranged from 10% ( G. etunicatum) to a maximum of 30% (Gi. gigantea, S. heterogama )
