By decomposing organic matter, bacterial communities are essential for plant growth and ecosystem functioning. Conversely, plants select for particular bacterial communities by depositing C resources belowground. These substrates are utilised by bacteria, which consequently drives soil C cycling. However, the exact mechanisms of this intimate relationship remain unclear. This book examines the effects of vegetation on bacterial community structure and whether plant driven differences in bacterial community composition affect C cycling in a grassland soil at the NERC experimental field site, Sourhope, Scotland. Four experiments were carried out to assess C cycling through basal soil respiration, substrate-specific respiration and priming effects measurements. Concurrently, soil bacterial communities were examined using a range of molecular techniques including stable isotope probing. This work highlights linkages between soil bacterial community composition and C functioning, and will be of interest to soil ecologists interested in above ground, belowground interactions.