Seasonal Climate Variations Promote Bacterial α-Diversity in Soil

Ecological theory suggests that temporal environmental fluctuations can contribute greatly to diversity maintenance. Given bacteria's short generation time and rapid responses to environmental change, seasonal climate fluctuations are very likely to play an important role in maintaining the extremely high alpha-diversity of soil bacterial community, which has been unfortunately neglected in previous studies. Here, with in-depth analyses of two previously published soil bacterial datasets at global scale, we found that soil bacterial alpha-diversity was positively correlated with both seasonal variations of temperature and precipitation. Furthermore, piecewise structural equation models showed that seasonal variations of temperature or precipitation had weak but significant positive effect on soil bacterial alpha-diversity in each dataset. However, it is noteworthy that the importance of seasonal climate variations might be underestimated in the above analyses, due to the potential confounding factors (such as vegetation type) and the lack of sampling across seasons. As a supplement, we analyzed a previously published wheat cropland dataset with samples collected in both winter and the following summer across North China Plain. As expected, bacterial alpha-diversity was positively correlated with seasonal climate variations in the cropland dataset, and climate seasonality explained a larger proportion of variations in bacterial alpha-diversity. Collectively, these findings implied that fluctuation-dependent mechanisms of diversity maintenance presumably operate in soil bacterial communities. Based on existing evidence, we speculated that the storage effect may be the main mechanism responsible for diversity maintenance in soil bacterial community, but rigorous experimental tests are needed in the future.

Automated summary

Research suggests that seasonal climate fluctuations play a role in maintaining high alpha-diversity in soil bacterial communities. Soil bacterial alpha-diversity is positively correlated with seasonal variations of temperature and precipitation, with weak but significant positive effects observed in different datasets.