A hollow bacterial diversity pattern with elevation in Wolong Nature Reserve, Western Sichuan Plateau

The pattern of eukaryotic macroorganisms varies with altitude is well-documented; by contrast, very little is known of how a bacterial pattern in soils varies with the elevation in a montane ecosystem. Mostly, previous studies on soil bacteria have either found a diversity decline, no trend, or a hump-back trend with increasing elevation. The aim of this study was to investigate the bacterial community composition and diversity patterns of Mount Nadu in Wolong Nature Reserve, Western Sichuan Plateau (3000-3945 masl). In total, 30 soil samples from the mountain at 10 sampling elevational zones (every 100 m from the baseband to the summit) were collected. High-throughput pyrosequencing approach was performed of soil bacterial 16S rRNA targeting V3 + V4 region by MiSeq PE300 and taxonomically classified based on Silva database. Bacterial community composition and diversity patterns were detected, and bacterial data were correlated with environmental factors to determine which factors influenced bacterial community composition. We obtained an average of 30,172 sequences per soil and found that the relative abundance of Acidobacteria and Proteobacteria count more than 70 % of the whole bacteria. Cooperative network analysis also revealed that Acidobacteria and Proteobacteria were important hubs in the community. Bacterial diversity pattern was found to be a significant hollow trend along altitudinal gradients and diversity of the dominant phyla (e.g., Acidobacteria, Proteobacteria) followed the results of the whole bacterial diversity. Moreover, distance-based linear model identified that soil pH and TN significantly provided 7.40 and 6.01 % of the total variation. The hollow trend of bacterial diversity has rarely been observed in nature. It indicated that no unifying bacterial diversity pattern can be expected along elevational gradients among the mountain system, and our result suggested the importance of environmental factors in structuring bacterial communities in this montane ecosystem.