Soil bacterial community structures across biomes in artificial ecosystems

Soil microorganisms are important for maintaining multiple functions of terrestrial ecosystems. Understanding the spatial and temporal distribution of soil microbial communities and their key determinants is one of the central goals of microbial ecology. In this study, we used an artificial ecosystem called the Ecorium, which a system with a series of biomes including tropical forest, desert, Mediterranean grassland and temperate forest. By using an artificial ecosystem, it is possible to understand the distribution of microbial communities and their key determinants under the control for potential confounds such as soil chronosequence, pedogenesis, ecosystem development stages and historical processes. Two years after construction of the Ecorium, we analyzed bacterial community structures using Illumina Miseq as well as measuring the chemical properties of the soil samples. The relationship between bacterial communities and soil chemical properties was then analyzed. Across all of the biomes, the most abundant phylum was Proteobacteria (36.0 ± 3.0%), followed by Actinobacteria (14.6 ± 3.1%), Bacteroidetes (12.4 ± 0.4%) and Acidobacteria (11.7 ± 3.2%). Bacterial alpha diversity was highest in the temperate biome and lowest in the control soil and desert biome. Bacterial community structure differed significantly between the control soil and that of the rest of the biomes, as well as among the biomes themselves. We found that the impact of climate factors was larger than that of biotic factors, such as vegetation diversity, in the structuring of bacterial communities. Soil water content appeared to be the most influential factor in determining microbial community structure. The results of this study provide a better understanding of the relationship and interaction between soil microbial ecology and environmental factors on a wide geographical scale. This information could be applied to technologies for ecosystem restoration, as well as the establishment of sustainable ecosystem management strategies and conservation policies.