Efficacy of native vesicular‐arbuscular mycorrhizal fungi after severe soil disturbance

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Abstract
SUMMARY: Field and greenhouse experiments were conducted to determine whether the VA mycorrhizal fungi present on a site before surface coal mining could form effective mycorrhizas in the disturbed soil on the site after mining. The disturbed soil had different physical, chemical and morphological characteristics than the soil on the site prior to perturbation.Artemisia tridentata subsp. WyomingensisBeetle and Young (Wyoming big sagebrush), inoculated or not with VA mycorrhizal fungi, was planted on the field site both as seed and as container‐grown seedlings. The native VA mycorrhizal endophytes produced only limited amounts of mycorrhizal infection in the disturbed soil (approximately 20% of total root length) and after 2 years were found to have no significant effect on the establishment, growth or survival of sagebrush plants. In the greenhouse study, mycorrhiza development and efficacy was compared in native sagebrush‐grassland soil and disturbed soil from the reclamation site with identical concentrations of mycorrhizal inoculum (19 propagules g−1). Mycorrhiza development in native soil greatly exceeded that in disturbed soil after 45 d growth (50vs.10% of total root length). Also, native mycorrhizal fungi effected significant increases in biomass production (+ 70%) and tissue phosphorus content (+ 70%) in sagebrush‐grassland soil but not in reclamation soil. The ecological implications of these results are discussed.