Spatially Varying Forest Productivity Associations with Temperature and Climatic Water-Balance Anomalies Along a Hydroclimatic Gradient in Northeast China

Forest productivity varies interannually in association with climate variability, but the strength and direction of these associations differ across hydroclimatic settings. Here, we examined how growing-season temperature and climatic water-balance anomalies covaried with forest net primary productivity (NPP) across persistent forests in Northeast China. Using harmonized 1 km data spanning 1985–2024, we applied pixel-wise correlations and a two-predictor association model to detrended and standardized time series, alongside original-unit sensitivity analyses. Climatic-water-balance associations exhibited a distinct hydroclimatic ordering: median water-balance–NPP correlations shifted from −0.082 in humid forests to 0.234 in semi-arid forests, with positive associations becoming progressively more prevalent toward drier forest margins. Temperature associations likewise shifted toward less positive or more negative values along the same gradient, although this pattern showed lower stability across analytical definitions. The water-balance ordering remained robust across alternative preprocessing choices and screening rules. Across all hydroclimatic zones, pixel-wise models showed modest explanatory power, with zonal median R2 ranging from 0.054 to 0.090. Overall, the direction and relative prominence of synchronous temperature and climatic-water-balance associations with NPP showed a consistent zonal ordering along the regional hydroclimatic gradient, indicating that spatially aggregated averages can obscure contrasting local climate–productivity patterns while the observed relationships remain descriptive rather than causal.