This dataset contains the input and processed data associated with the study “Water availability weakens the forest litter carbon sink”. Input datasets are provided during peer review as Supporting Information and include raw measurements and environmental data. Processed outputs include: Modeled litter carbon decomposition rates Coefficient of variation (CV) of decomposition rates Pixel-level CV derived from 100 random forest model iterations Estimates of litter carbon release and sink All datasets are openly available, hosted on Zenodo, and distributed under a CC BY 4.0 license. A permanent DOI is assigned for proper citation. These data are fully accessible without restriction and comply with FAIR principles (Findable, Accessible, Interoperable, Reusable).