PNNL

The Science                                 

Soil microbes drive local-to-global cycles of carbon, nutrients, and greenhouse gases, but there is relatively limited understanding of how specific groups of microbes are linked to major changes in environmental conditions. A new study finds that, across deserts and grasslands, there are clear associations between environmental conditions and the diversity and abundance of two groups of soil microbes—Haloarchaea and ammonia-oxidizing archaea (AOA). The study also found a clear distinction in the ecological processes responsible for the spatial patterns of these two groups. Haloarchaea were governed primarily by deterministic selection-based processes while AOA were assembled mostly by stochastic (i.e., random) movement.

The Impact

This study adds to existing knowledge of large-scale biogeography and ecology of soil microbes, advancing scientists’ ability to predict changes in soil microbial communities in a drier world. Relative to previous work, this study spanned a large geographic domain: 3,500,000 km² across northern China. This scale is important because it indicates that the results are likely to be transferable to other dryland systems across the Earth. In addition, researchers used cutting-edge ecological theory and analytical tools to provide deep insights into processes governing the ecology of soil microbes. The team also developed models that showed good predictive power and they could be used to simulate changes in microbial distributions (and the biogeochemical functions they provide) under future climate scenarios.

Summary

This work contributes to a previously limited understanding on the large-scale biogeography of Haloarchaea and AOA in drylands. Researchers consider it original and significant, as it reveals strong ecological differentiation between these two dominant topsoil archaeal groups—primarily driven by habitat specialization associated with contrasting ecosystem types (i.e., deserts and grasslands) rather than small-scale microsites (i.e., bare ground and vegetated areas). Moreover, this work also provides new insights into the community assembly processes underpinning the distinct biogeographical patterns of Haloarchaea and AOA. It reveals that the distribution of Haloarchaea is mainly determined by environmental-based processes, while AOA are more influenced by stochastic (i.e., random) spatial-based processes. These observations are important under future climatic scenarios and suggest that topsoil archaeal communities will likely change due to climate forecasts for drylands worldwide.

Funding

This research was supported by the National Natural Science Foundation of China (nos. 31700463 and 31770430), National Scientific and Technological Program on Basic Resources Investigation (no. 2019FY102002), Biodiversity Survey and Assessment Project of the Ministry of Ecology and Environment, China (no. 2019HJ2096001006), National Youth Top-notch Talent Support Program to J.D., and the Innovation Base Project of Gansu Province (no. 20190323). J.C.S. was supported by the Department of Energy’s Biological and Environmental Research program, as part of an Early Career Award to J.C.S. at the Pacific Northwest National Laboratory, a multi-program national laboratory operated by Battelle for the Department of Energy under Contract DE-AC05-76RL01830.