When viewed from above, the distribution of individuals over the landscape can be visualized as a pattern of tiny dots dispersed over a blank area. More modern advances in molecular sciences are now used to address these issues.An alternative way of describing spatial distributions is to move the focus to the position of separate individuals in space. For this reason, there is a heightened interest in plant and agronomic effects on soil bacterial biodiversity. However, because of the increasing demand for food production, one factor that is heavily altered by human populations is the plant communities. It is difficult, perhaps even impossible, to determine the relative importance of each of the different factors in driving soil biodiversity, because of their inherent interdependencies. In the short term, plants provide labile exudates from their roots, which feed the bacterial activities and the local diversity of communities. Soil bacterial communities are also driven by plant diversity which provides the important raw detrital materials on which the microbial communities build the soil. In more neutral habitats, like those favoured for agriculture, there are more diverse assemblages of bacteria that are better-known due to culture-based studies. This biodiversity is made up of many previously undiscovered taxa, such as the acidobacteria, which are specialised for living in such physiologically harsh environments. Across landscape gradients, from upland bogs and woodlands through grasslands to intensive lowland arable systems, predictable changes occur in the broad taxonomic makeup of bacterial communities which can be related to changes in soil properties, such as acidity and organic matter content. These findings are now being complemented by data from large-scale soil surveys using molecular techniques to assess biodiversity.Ī striking consistency in the many large-scale studies that have been performed is the overriding influence of soil properties on soil bacterial communities. In the past, our knowledge of the different types of bacteria found in soil, and the factors affecting their distributions, has been limited to findings from the analyses of culturable bacteria that can grow on nutrient-rich media in the laboratory. They are able to grow rapidly and, therefore, can adapt rapidly to environmental change. Bacteria play important roles in the plant-soil system firstly, by both fixing and transforming nutrients vital to other organisms, but also by influencing the overall ecology of the system through positive or negative biotic interactions with other organisms. To date, it is impossible to come to sound conclusions about the rank of environmental filters driving the soil microbial assembly to a large extent.īacteria are by far the most abundant organisms in soils, with several thousand million cells present in a single gramme of most soils. The fact that more than a trillion microorganisms are transported annually through the atmosphere between continents supports the hypothesis of a wide dispersion of microbes. Microbial ecologists describing the distribution of soil microorganisms on a large spatial scale generally invoke one of the oldest fundamental paradigms in microbial ecology ‘everything is everywhere, but, the environment selects’. Distribution of soil microbial communities