The plant communities of the semiarid southwest region of the US have been in transition for the last 100-yrs, as woody plants encroach into historic grasslands. This change leads to important questions regarding alterations of the ecosystem functioning. Since microorganisms are primary actors of biogeochemical dynamics, understanding the relationship between microbial and plant diversity and ecosystem function, is of major relevance. Thus, the main goal of this work was to evaluate the consequences that vegetation change in semiarid ecosystems has in diversity and composition of microbial communities, and how is this related with changes in climate conditions. In order to address these questions, a large-scale mesocosm experiment was established and maintained during two years within the Biosphere 2 facility in Oracle, Arizona. Two habitats were established and maintained at a 4°C difference (the warmer biome setting serve as a proxy for future climate conditions) and two types of plants (either grass or mesquite) were planted in each of them. Soil samples were taken at the beginning and the end of the experiment to evaluate changes in microbial community composition using a metagenomic approach. The microbial species were identified by the sequencing of the 16S rRNA gene.
Results/Conclusions
Diversity analysis of the microbial communities present in the soil samples showed two main findings: 1) regardless of the climate regime, microbial alpha diversity increases in the presence of vegetation in comparison with the original soil and, 2) microbial community structure (evaluated using UniFrac distances) is related to the vegetation type (grass vs mesquite) but not to the climate regime. Our results show that there is a direct impact of the vegetation change in the diversity and composition of associated soil microbial communities, which could imply major changes in biogeochemical processes and thus ecosystem scale impacts.