Understanding the biogeochemical cycling of carbon (C) and other major nutrients (N, P, S) is critical within the Earth’s Critical Zone, which spans from soils and sediments to aquifers and aquatic systems, as changes in these cycles affect greenhouse gas emissions, biodiversity, and ecosystem functioning. These cycles often involve reduction-oxidation (redox) reactions, and regulation of them is particularly crucial in the face of environmental perturbations such as warming, overfertilization, and salinization. As these cycles are dynamic and interlinked, it is often difficult to disentangle the underlying processes and their response to often interactive environmental perturbations. In this session, we invite contributions that investigate the (redox) biogeochemical cycling of carbon, nitrogen, phosphorus, and sulfur in the critical zone. We welcome laboratory and field-based studies as well as modeling approaches that explore mechanisms, controls, and process responses under global change scenarios. Studies that link microenvironments to bulk ecosystem behavior or couple geochemical reactions with hydrology are of particular interest. We especially encourage integrative approaches that bridge scales and methods to advance mechanistic insight and predictive understanding of ecosystem functioning.