Soils are a constellation of hotspots of biological activity, such as the (mycor)rhizosphere, drilosphere, detritusphere, etc, that contribute considerably to emerging properties and ecosystem processes at larger scales. This session addresses all biogeochemical processes at these unique interfaces with focus on, but not limited to, carbon and nutrient (N, P, K, S, micronutrients) cycling. Spatial and temporal dynamics shaping these hot spots of biological activity as well as stoichiometric constraints involved in the coupling/decoupling of processes and cycles will be discussed.