Local patterns of arbuscular mycorrhizal fungal diversity and community structure in a natural Toona ciliata var. pubescens forest in South Central China

Toona ciliata var. pubescens (Toona in Meliaceae) (Tc) is listed as an endangered species, and there are natural regeneration obstacles due to its long-term excessive exploitation and utilization. Arbuscular mycorrhizal fungi (AMF) can produce beneficial effects for plant growth and natural regeneration. However, the characteristics of the AMF community in natural Tc forests are poorly understood. The Illumina PE250 high-throughput sequencing method was used to study the characteristics of the AMF community in the rhizosphere soil and roots associated with three dominant tree species (Tc; Padus buergeriana, Pb; and Maesa japonica, Mj) in a natural Tc forest in Guanshan National Natural Reserve, South Central China. The results found that Glomeraceae was the most abundant AMF family in the rhizosphere soil and roots. Moreover, the relative abundance of Archaeosporaceae in rhizosphere soil was significantly larger than that in the roots; in contrast, the relative abundance of Glomeraceae in rhizosphere soil was significantly lower than that in the roots (p < 0.05). Regarding different tree species, the relative abundances of Acaulosporaceae and Geosiphonaceae were larger in Mj and Tc than in Pb. AMF operational taxonomic units (OTUs) were 1.30-, 1.43-, and 1.71-fold higher in the Tc, Pb, and Mj rhizosphere soil, respectively, than in the corresponding roots. Nevertheless, higher AMF community richness was found in the roots compared to that in the rhizosphere soil based on the Chao index. This finding indicated that AMF of a relatively high aggregation degree were in roots, and more AMF groups with relatively low abundance occurred in the rhizosphere soil, which correspondingly lowered the calculated richness index of the AMF community. A redundancy analysis showed that different soil chemical properties impacted variations in the AMF community characteristics differently. This study has great significance for the interpretation of AMF diversity survey and the application design of AMF in vegetation restoration.