Hydrologic processes control ecosystem function from leaves to landscapes. At the leaf scale, hydraulic supply from the soil-plant continuum governs stomatal regulation, thereby constraining carbon gain and energy partitioning. At the root-zone scale, soil moisture governs evapotranspiration, photosynthesis, and microbial activity, driving coupled carbon-nutrient-water cycling. At the catchment scale, runoff–infiltration regulates carbon and nutrient transport and retention. At regional scales, land surface water balance shapes atmospheric moisture recycling and energy fluxes, feeding back to the climate system. This session invites contributions advancing process-based understanding through observations, experiments, and models, including developing theory, revealing emergent behavior, or uncovering causal mechanisms. Relevant concepts include, but are not limited to, stochastic variability (e.g., rainfall intermittency–soil moisture feedbacks), optimality (e.g., efficient resource use in water-limited ecosystems), nonlinearity (e.g., hydraulic failure, carbon cycling hysteresis), biological adaptation to water variability (e.g., deeper rooting, microbial reassembly), and ecosystem self-organization (e.g., spatial patterns of water, carbon, and nutrients).

• B - Biogeosciences
• GC - Global Environmental Change