[Simulation of Future Trends of Net Primary Productivity in Major Grain-producing Provinces Based on Machine...

Net primary productivity （NPP） is a vital indicator of ecosystem health， directly influencing the global carbon cycle and climate regulation， and is closely related to regional food production. In the context of global climate change， research on the spatiotemporal changes and driving factors of NPP in major grain-producing areas is limited. Therefore， this study selected Henan Province and Heilongjiang Province， two significant grain-producing provinces， to explore the differences in NPP changes and their driving factors from 2001 to 2020. Various machine learning algorithms were employed to estimate NPP and simulate its evolutionary trends under future climate scenarios based on shared socioeconomic pathways （SSPs）. The results follow： ① Compared with the single algorithm， the weighted fusion of the prediction results of the AdaBoost and XGBoost algorithms can more accurately estimate the NPP of the two provinces. This approach significantly reduces the root mean square error and improves the goodness of fit. ② From 2001 to 2020， NPP in Henan Province showed an increasing trend， with higher values in the west and south and lower values in the north. Similarly， during this period， NPP in Heilongjiang Province also exhibited an upward trend， with high-value areas located in the northern， central， and southern forest regions and low-value areas in the western regions characterized by high urbanization rates. ③ In Henan Province， precipitation emerged as the most important climate driver affecting changes in NPP. The interaction between lower temperatures and reduced potential evapotranspiration enhances the positive impact of precipitation on NPP. In contrast， potential evapotranspiration is the primary driving factor for NPP changes in Heilongjiang Province， where lower levels of potential evapotranspiration and annual mean temperature contribute to increased NPP. ④ Under the SSP245 and SSP585 scenarios， NPP in both provinces is projected to decline， with a more significant reduction under the SSP585 scenario. The continuous increase in temperature poses a substantial threat to NPP in both provinces. Therefore， proactive measures should be taken to mitigate the negative impacts of declining NPP in the future.