Soil contains twice as much carbon as the atmosphere and three times that of global vegetation thus making it the largest reservoir of terrestrial carbon1. Enhancing the potential of agricultural soils to sequester C has implications for decreasing atmospheric CO2 as well as impacting on nutrient cycling and soil erosion. Soil organisms play a well-recognised role in soil C cycling and sequestration with a number of recent studies indicating that stable organic matter (OM) in soil is likely of microbial origin2. Microbial decomposition of soil OM varies with inherent soil properties, for example pH, OM quality, and resident microbial communities and their functions. While the role of bacteria and fungi in OM decomposition has been the subject of numerous studies, the dynamics and functioning of the microorganisms involved remain under explored. In particular the succession and co-occurrence patterns of soil microbial communities during decomposition are poorly understood. Here we investigated, over the course of a six month incubation experiment, the influence of soil pH and the quality of plant residue inputs on the dynamics and successional patterns of the microbial decomposer communities and the networks they form. We utilised a barcoded sequencing approach and network asoilnalysis of bacterial 16S rRNA and fungal ITS genes to determine the key microbial groups involved in residue decomposition as well as to characterise their co-occurrence patterns. As soil microbial communities mediate OM decomposition through the actions of their enzymes we also assessed OM and plant residue decomposition processes by determining the abundance of some of the genes associated with this process, for example laccases involved in lignin decomposition and cellobiohydrolases involved in cellulose decomposition. There were significant shifts in community structure for both bacteria and fungi with residue amendment and over time with the abundance of key taxa significantly (P<0.05) impacted, for example Acidobacteriaceae, Cytophagaceae and Oxalobacteraceae. Network analysis is ongoing but preliminary work shows pH related differences in co-occurrence patterns exist in these communities.