Abstract
Ecological understandings of soil bacterial community succession and assembly mechanism along elevational gradients in mountains remain not well understood. Here, by employing the high-throughput sequencing technique, we systematically examined soil bacterial diversity patterns, the driving factors, and community assembly mechanisms along the elevational gradients of 1800–4100 m on Gongga Mountain in China. Soil bacterial diversity showed an extraordinary stair-step pattern along the elevational gradients. There was an abrupt decrease of bacterial diversity between 2600 and 2800 m, while no significant change at either lower (1800–2600 m) or higher (2800–4100 m) elevations, which coincided with the variation in soil pH. In addition, the community structure differed significantly between the lower and higher elevations, which could be primarily attributed to shifts in soil pH and vegetation types. Although there was no direct effect of MAP and MAT on bacterial community structure, our partial least squares path modeling analysis indicated that bacterial communities were indirectly influenced by climate via the effect on vegetation and the derived effect on soil properties. As for bacterial community assembly mechanisms, the null model analysis suggested that environmental filtering played an overwhelming role in the assembly of bacterial communities in this region. In addition, variation partition analysis indicated that, at lower elevations, environmental attributes explained much larger fraction of the β-deviation than spatial attributes, while spatial attributes increased their contributions at higher elevations. Our results highlight the importance of environmental filtering, as well as elevation-related spatial attributes in structuring soil bacterial communities in mountain ecosystems.
Highlights
Unraveling the drivers and mechanisms of community succession and community assembly along ecological gradients are two major goals in ecology (Chase, 2003; Zhou et al, 2014)
We looked into the composition and diversity of soil bacteria along the elevational gradients from 1800 to 4100 m in Gongga Mountain
The results showed minor difference with a recent report that pH 5 probably could be as the threshold below which soil bacterial diversity might decline and bacterial community structure might change significantly (Xia et al, 2016)
Summary
Unraveling the drivers and mechanisms of community succession and community assembly along ecological gradients are two major goals in ecology (Chase, 2003; Zhou et al, 2014). Climate, vegetation and soil properties vary drastically over short spatial distance (McCain and Grytnes, 2010). Elevational gradients can serve as a natural platform to reveal potential microbial responses to climate change with a strategy of space-for-time substitution (Dunne et al, 2004). Elevational biodiversity patterns for macro-organisms have been extensively recorded (McCain and Grytnes, 2010), which shows maximum diversity at lower or middle elevations. The elevational diversity patterns of microbial communities appear to be more divergent, such as increasing (Wang J. et al, 2017), decreasing (Bryant et al, 2008; Shen et al, 2015; Wang J.-T. et al, 2015), and mid-elevation patterns (Singh et al, 2012a,b), or no consistent pattern (Fierer et al, 2011; Shen et al, 2013). The elevational patterns of soil microbial communities in a mountain ecosystem remain controversial
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