Spatiotemporal Evolution and Stability Risks of Net Ecosystem Productivity in the Yellow River Basin

Terrestrial carbon sinks in water-limited basins may strengthen while remaining vulnerable because gains in vegetation productivity can be offset by climate-sensitive soil carbon losses. Here, we present a model-derived assessment rather than a direct observation of basin carbon exchange. Using MODIS NPP, ERA5-Land climate data, OpenLandMap SOC, a semi-empirical total-soil-respiration model, and an empirical Rh–Rs conversion for 2001–2024, we quantified NEP, decomposed its component fluxes, characterized historical trend persistence, and tested the sensitivity of source–sink and risk-zone classifications to prescribed respiration and productivity perturbation scenarios. All annual means, totals, and trends were recalculated on the GEE annual common valid-pixel mask with identical area weights; local spatial class tables use their separately reported raster mask. The baseline multi-year mean NEP was 16.71 g C m−2 yr−1 and the mean annual total was 13.24 Tg C yr−1. Increasing Rh by 10% changed mean NEP to −11.10 g C m−2 yr−1, demonstrating that the inferred basin-wide sink is weak and highly sensitive to respiratory-flux assumptions. Hurst exponents are used only as statistical descriptors of historical dependence, not as deterministic forecasts. The framework identifies areas with historically positive net flux, potential enhancement, and reversal risk, while explicitly qualifying their uncertainty and management relevance.