Abiotic and Biotic Factors in Coal Mine Soils Influence Ectomycorrhizal Composition and Symbiosis

Surface mining for coal leads to significant changes in ectomycorrhizal (ECM) fungal community composition by removing host plants and altering the structure and chemistry of the soil environment.These changes impact ECM fungal composition and efficiency of ectomycorrhizal formation.This study investigates the influence of soil abiotic factors on ECM community composition and root colonization.Two different surface coal mine sites in Ohio, U.S.A. were used: an abandoned surface mine and a site reclaimed under the Surface Mining and Control Act of 1977.Within the abandoned site, three unique conditions were delineated: 1) remnant forest edge, 2) restoration plots consisting of Pinus virginiana, and 3) non-vegetated sites.American chestnut (Castanea dentata Marsh.Borkh) were sown as nuts for use as ECM trap trees.The presence and identity of native ECM were determined by fungal DNA sequencing of the internal transcribed spacer (ITS) region.Relationships between fungal genera and soil characteristics were determined by a non-metric multidimensional scaling (NMDS) ordination.A multiple regression was used to determine which soil variables influenced ECM root colonization.Results illustrated significant differences between the abandoned mine soils when compared to the reclaimed soils in terms of pH, phosphorus, and potassium.ECM fungal composition was dependent upon the levels of phosphorus, organic matter, and magnesium in the soil.Certain ECM genera were associated with higher phosphorus and pH, while some were linked to nutrient impoverishment.Differences existed between two ectomycorrhizal fungal species within the Scleroderma genera, suggesting that not all species within a genus share environmental preferences.Organic matter was a significant predictor of ECM root colonization.Knowledge of these factors will be helpful for designing suitable mine reforestation strategies such as prediction of ECM fungi, use of ECM inoculum, and soil amendments.