Determining the Influence of Environmental Factors upon Dominant Soil Bacterial Taxa and Functioning

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Bacteria constitute a major portion of the biodiversity and biomass in soils and consequently they play an essential role in maintaining soil processes which, ultimately, regulate the functioning of terrestrial ecosystems. The use of molecular techniques has permitted a greater understanding of the identities of dominant bacteria present in a range of soil types, though there is still a lack of understanding as to what drives this diversity on a large geographic scale. In addition, there is no clear consensus on how alterations in bacterial biodiversity impacts on ecosystem functions such as the mineralization of carbon. Such knowledge is essential to improving our understanding of the controlling factors behind a range of soil processes, and in addition may provide a fundamental framework for the future use of biological indicators of soil quality. Recently it has been shown that pH is the main driver in determining the richness of bacterial taxa in soil communities, and additionally there is an emerging hypothesis that the nutrient status of the soil dictates the ratio of two abundant groups of soil taxa. We aim to disentangle this relationship in a diverse range of soil types. Specifically we seek to firstly asses the role of pH in determining the identities of dominant soil bacteria, and then we will address how different nutrient inputs determined by aboveground vegetation, and additional environmental variables affect soil bacterial biodiversity. We will do this by assessing all soil samples taken as part of the Countryside Survey (CS) 2007. These soil samples will be thoroughly characterised with respect to soil chemistry and overlying vegetation as a core element of the Countryside Survey. Using these soils will allow us to correlate several key soil variables with specific changes in members of the bacterial community. Whilst we wish to address fundamental questions on the controls of soil bacterial community diversity, we also seek to question the usefulness of microbial indicators of soil functionality. Therefore, once taxonomic relationships have been established, we will select subsets of samples purely on the basis of similarity of bacterial composition/diversity, and measure carbon mineralization rates to determine whether communities of similar bacterial diversity confer similar functional abilities.