Ectomycorrhizal fungal community assemblage under various soil reclamation methods

Background/Question/Methods

Ectomycorrhizal fungal (ECM) community assemblage is an integration of many abiotic and biotic factors.  The community patterns of ECM fungi may be a response to the soil environmental conditions, but how these factors interact to influence ECM root colonization and community structure is not fully understood.  The objective of this study was to use environmental data and planting methods to determine variables that influenced ECM community composition and root colonization of American chestnut (Castanea dentata).  Three different surface coal mines in central Ohio were assessed.  The first site is an abandoned surface coal mine that was reclaimed in the 1950s.  The second site was mined in the late 1970s and reclaimed under The Surface Mining Control and Reclamation Act (SMCRA).  The third site was reclaimed in the early 2000s using the Forest Reclamation Approach of soil end dumping. Pure American chestnuts were planted as seed and sampled for ECM root colonization.  Root morphotyping and DNA sequencing of the fungal internal transcribed spacer region was used to identify the ECM species. Differences in species composition per soil characteristics were determined by fitting environmental vectors onto an ordination.  Multiple regressions were used to determine which soil variables influenced ECM root colonization.  

Results/Conclusions

Analysis of soil variables demonstrated a clear separation among the three different types of reclamations (P < 0.0001).  Grasslands in the SMCRA reclaimed mine site were significantly higher in soil pH and phosphorus (P = 0.04).  Although SMCRA reclamation methods have been criticized for resulting in arrested succession, there were noted improvements when compared to the other soils. Organic matter, existing vegetation, and soil manipulations significantly contributed ECM root colonization (P = 0.03). Species composition was driven by soil phosphorus, organic matter, and magnesium. Ordination patterns showed a clustering of ECM communities within respective sites.  This pattern was supported by a permutational multivariate analysis of variance, which showed a strong site effect (P = 0.005).  Differences in ECM communities were associated with differences in nutrient availability; this may have catalyzed a shift in fungal communities to species better able to persist in acidic soils under nutrient-limited conditions.   In addition, certain species appeared not to exist as mycelium on existing vegetation, but have the ability to rapidly recruit after mechanical soil treatments.  Proper site selection and planting methods significantly contributed to ECM root colonization on chestnut in abandoned and reclaimed mine sites in central Ohio.