[Bacterial diversity of different successional stage forest soils in Dinghushan]

The aim of the present study was to investigate the soil bacterial diversity of pine forest (PF), pine-broadleaf mixed forest (MF) and monsoon evergreen broadleaf forest (MEBF), the typical forest types that represent early, middle and late successional stage forests in Dinghushan, respectively. The results obtained will also provide information for further examination of the relationship between the soil bacterial diversity and ecological function of the forests.

Three total DNA samples were extracted directly from soil samples collected from PF, MF and MEBF, and then the 16S rDNA sequences were PCR amplified and the libraries were constructed, respectively. For each of the three libraries constructed, 150 positive clones were picked randomly and the inserted 16S rDNA were sequenced. The soil bacterial diversity of the forests was analyzed by Mothur based on the sequences obtained.

A total of 122, 118 and 120 valid 16S rDNA sequences were obtained from PF, MF and MEBF, which represented 70, 64 and 72 operational taxonomic units (OTUs, definition at a level of 97% similarity), respectively. Bacteria belonging to 8 phyla were identified. Among them, Acidobacteria accounted for 53.3%, 67.8% and 60%, while Proteobacteria took up 29.5%, 20.3% and 32.5% in PF, MF and MEBF, respectively. The other bacterial phyla identified each accounted for less than 10%. The bacterial community structure differed significantly at species level among three soil samples (P < 0.05) with the percentages of the shared OTUs between any two soil samples lower than 25%. MEBF had the highest Chao index (414.2), Shannon index (3.90) and the lowest Simpson dominance index (0.0249).

The soil bacterial community structure differed significantly at species level among PF, MF and MEBF in Dinghushan, while they have a similar structure at phyla or class levels with Acidobacteria predominated followed by Proteobacteria.