Plant associated soil microbial communities play a critical role in productivity of Earth's ecosystems as they ensure cycling of key elements. Specifically, plant biodiversity losses alters soil microbial communities and can have significant consequences for plant resistance to biotic and abiotic stress. Across a biodiversity gradient this thesis found that bacterial communities are uncoupled from plant diversity. However, specific groups of bacteria respond to changes in plant diversity. Plant and soil factors clearly favoured different bacterial groups and notably on the lines of their growth strategies, with plants selecting fast growing species and negatively influencing groups that are antagonistic and slow growing. Furthermore, plant diversity not only altered fungal diversity but demonstrated specific effects on fungal guilds. Due to the highlighted importance of fungal association a pot experiment controlling for AMF association was also carried out to observe effects of the fungal association on decomposition of stoichiometrically similar organic matter types and examine carbon-nitrogen trade between plant and associated microbial community. Arbuscular mycorrhizal Fungi (AMF) associated plants allocated more carbon to their roots but due to assistance of AMF incurred a lower cost of nutrient acquisition. Additionally, distinct microbial communities were fostered in presence of symbiotic fungal associations possibly explaining the amount of carbon used for exchange of nutrients from decomposing organic matter. In conclusion, the data compiled in this thesis shows plant diversity and their microbial association related traits are important modifiers of soil microbial communities. In summary, in a multispecies environment microbial associations are a fundamental part of efficient nutrient acquisition from decomposing organic matter in soil.