Responses of the Key Phenological Characteristics and Carbon Flux of Winter Wheat to Climatic Time-Lag Effects and Crop Management on the North China Plain

Evaluation of the net ecosystem exchange (NEE) of agroecosystems may help to assess regional carbon cycles and ensure carbon neutrality. However, farmland NEE is influenced by climate change, phenological period, and crop management. Therefore, in this study, we investigated the time-lag effects of climate change on the phenology and NEE of winter wheat, as well as the influence of crop management. We found that the impact of climate change on the phenology of winter wheat exhibits a time lag of 1 to 2 months, with notable spatial and temporal heterogeneity. When accounting for time-lag effects, the correlation between climate change and both phenology and NEE significantly strengthens, with the lagged impact on NEE primarily mediated through changes in phenology. Specifically, climate change accelerates the green-up and heading dates but delays the maturity date, while crop management extends the phenological period. Our findings indicated that during the green-up stage, NEE is mainly influenced by temperature changes resulting from climate change. During the heading stage, it is predominantly affected by crop management, and during the maturity stage, it is impacted by both factors, with crop management having a more significant effect. Overall, the accelerated green-up stage and delayed heading and maturity stages contribute to enhanced carbon sequestration. This research provides new insights into carbon exchanges in agricultural ecosystems.