Temperature-VPD-evapotranspiration interactions modulated asynchronous dynamics of vegetation photosynthesis and net ecosystem production in Eurasia

While global vegetation shows widespread greening under climate change, the corresponding impacts on Net Ecosystem Production (NEP)—particularly the divergent responses between drylands and non-drylands—remain poorly understood. In this study, based on the Normalized Difference Vegetation Index (NDVI), Solar-Induced Chlorophyll Fluorescence (SIF), Gross Primary Productivity (GPP), and NEP, we analyzed the spatiotemporal dynamics of vegetation photosynthesis and NEP across Eurasia from 1982 to 2018, and explored their differential responses to environmental factors, with particular focus on the contrasting mechanisms between drylands and non-drylands. The results showed that the rate of increase in NEP standardized anomalies (0.004 yr−1, p < 0.05) lagged behind NDVI/SIF/GPP standardized anomalies (0.009 − 0.014 yr−1, p < 0.01), particularly after 2000, and it was more pronounced in drylands. Spatially, vegetation photosynthesis and NEP changed asynchronously in nearly one-third of Eurasia, with a slightly higher proportion in non-dryland areas and the most obvious patterns in forests and croplands. Explainable machine learning analysis revealed that this asynchrony was primarily driven by interactions among temperature, vapor pressure deficit (VPD), and evapotranspiration. Vegetation photosynthesis was mainly influenced by evapotranspiration, while NEP was constrained by increased VPD. Moreover, in drylands, NEP was highly sensitive to atmospheric moisture, whereas in non-drylands, temperature fluctuations played a dominant role. These findings offer important insights for regional carbon sequestration management and climate change adaptation strategies.