Arbuscular mycorrhizal fungal community differentiation along a post-coal mining reclamation chronosequence in South Africa: a potential indicator of ecosystem recovery

Abstract

Arbuscular mycorrhizal (AM) fungi contribute to the restoration of soil ecological functions and processes during ecosystem development. Here, diversity and differentiation of AM fungi in rhizosphere soils and roots of the dominant vegetation along a post-coal mining reclamation soil chronosequence of 3, 11, 15, 19 and 24 years after reclamation were investigated. High-throughput sequence analysis of partial Glomeromycotan 18S rRNA in soils and roots revealed a high number of core operational taxonomic units (OTUs) across chronosequence. Arbuscular mycorrhizal fungal (AMF) OTU richness, Shannon-Weiner index and species dominance were not significantly different across soil and root but were significantly (P < 0.05) correlated with ammonium, nitrate, silt fraction, litter, pH, foliar and/or basal covers. AMF community structure was significantly different (P < 0.05) across unmined and reclamation chronosequence soils, with differentiation between younger reclaimed areas (3 and 11 years) and older reclamation ages (19 and 24 years) in multivariate space. In contrast, structural differentiation in the AMF community colonising the single plant-host across the chronosequence was not significant (PERMANOVA, P > 0.05), although community composition and structure were heterogeneous within 3–11 years but similar within 15–24 years. Seven Glomeromycotan genera were detected in soil and roots, including the relatively dominant Glomus genus, and the differentially abundant Acaulospora, Diversispora, Paraglomus and Scutellospora in either earlier or later years since post-mining reclamation. Canonical correspondence analysis revealed that nitrates (NO3-N), clay content and bulk density significantly influenced (P < 0.05) the AMF community structure in soil, whereas, the AMF community in root was not significantly influenced (P > 0.05) by environmental variables. Overall, the study suggests that AMF community differentiation reflect ecosystem development over chronological space-time. Thus, AMF species differentiation may be included as part of a minimum dataset for monitoring ecosystem restoration following post-mining reclamation