The bacterial biogeography of British soils

TLDR

Soil bacteria are essential to ecosystem functioning, yet consensus on the factors regulating belowground biodiversity remains limited. This study maps bacterial community profiles across Great Britain using over 1,000 soil cores, providing the first landscape‑scale bacterial distribution map. The authors assessed community composition via terminal restriction fragment length polymorphism and clone libraries, integrating soil chemistry, vegetation, and climate data across multiple spatial scales. Bacterial diversity and dissimilarity were strongly linked to soil pH, with α diversity increasing and β diversity peaking in acidic soils dominated by Acidobacteria and Alphaproteobacteria, while additional correlations with soil chemistry, vegetation, climate, and spatial proximity revealed that bacterial communities mirror plant communities and that broad‑scale surveys delineate distinct, reproducible soil biomes.

Abstract

Summary Despite recognition of the importance of soil bacteria to terrestrial ecosystem functioning there is little consensus on the factors regulating belowground biodiversity. Here we present a multi‐scale spatial assessment of soil bacterial community profiles across Great Britain (> 1000 soil cores), and show the first landscape scale map of bacterial distributions across a nation. Bacterial diversity and community dissimilarities, assessed using terminal restriction fragment length polymorphism, were most strongly related to soil pH providing a large‐scale confirmation of the role of pH in structuring bacterial taxa. However, while α diversity was positively related to pH, the converse was true for β diversity (between sample variance in α diversity). β diversity was found to be greatest in acidic soils, corresponding with greater environmental heterogeneity. Analyses of clone libraries revealed the pH effects were predominantly manifest at the level of broad bacterial taxonomic groups, with acidic soils being dominated by few taxa (notably the group 1 Acidobacteria and Alphaproteobacteria). We also noted significant correlations between bacterial communities and most other measured environmental variables (soil chemistry, aboveground features and climatic variables), together with significant spatial correlations at close distances. In particular, bacterial and plant communities were closely related signifying no strong evidence that soil bacteria are driven by different ecological processes to those governing higher organisms. We conclude that broad scale surveys are useful in identifying distinct soil biomes comprising reproducible communities of dominant taxa. Together these results provide a baseline ecological framework with which to pursue future research on both soil microbial function, and more explicit biome based assessments of the local ecological drivers of bacterial biodiversity.