Climate pattern–land use pathways shape dissolved organic matter dynamics in the Pearl River Basin

Static models relying solely on land use are increasingly insufficient for predicting riverine dissolved organic matter (DOM) dynamics. Here, we address this limitation by proposing the Climate Pattern–Land Use Pathways (CPLUP) framework to disentangle the synergistic interactions between climatic drivers and land use. We developed this framework using a synoptic dataset from the Pearl River Basin (PRB, n=228) and validated it globally via a machine learning ensemble. In the Pearl River Basin, we observed that terrestrial signatures dominated the entire river network, whereas autochthonous signals significantly increased in the downstream reaches. Attribution analysis revealed that this spatial divergence was driven by climatic forces that activate static land-use sources. Specifically, high discharge provided the kinetic energy to mobilize terrestrial organic matter from land into rivers, representing a process limited by transport capacity. Conversely, solar radiation and temperature provided thermodynamic energy to catalyze biochemical transformations within the water column, representing a process limited by reaction kinetics. Building on these mechanistic insights, we established the CPLUP framework to explicitly map how distinct climatic drivers regulate specific land-use signals. By decoding these complex dynamics, our study provides a robust predictive tool (CPLUP) for forecasting riverine DOM under intensifying climate change and urbanization.