Integrated effects of meteorological factors, edaphic moisture, evapotranspiration, and leaf area index on the net primary productivity of Winter wheat − Summer maize rotation system

Net primary productivity (NPP) assumes a pivotal role in the realm of plant growth, organic matter production, and carbon cycling. Nevertheless, the mechanism underlying the integrated effects of meteorological factors, soil water content (SWC), evapotranspiration (ET), and leaf area index (LAI) on the NPP in agricultural systems remains unclear. Elucidating the evolution pattern of NPP in agricultural system and its responding mechanism to meteorological factors, SWC, ET, and LAI hold pronounced significant for sustainable agricultural operation, agroecological maintenance, and climate-adaptive strategy optimization. This study focused on the winter wheat - summer maize rotation, a predominant agricultural system, in the North China Plain (NCP). Spatiotemporal pattern of NPP was clarified using geostatistical technique, Mann-Kendall test, Sen's Slope, and Rescaled Range analysis. The mechanism underlying the integrated response of NPP to different meteorological factors, SWC, ET, and LAI was revealed through spatiotemporal coupling correlation analysis, Random Forest, and Structural Equation Modeling. The results demonstrated a widespread annual increase in NPP across the majority of rotation areas from 2000 to 2019, with a prominent geospatial heterogeneity. Meteorological factors, SWC, ET, and LAI collectively explained 70.27% of NPP variability. Of which, ET, FAPAR, P, LAI, Tmax, Tmin, and the SWC in 40–100 cm were predominant factors affecting NPP, explaining 63.59% of its variability. These factors exerted multidimensional effects on NPP, instead of a unilateral induction. Despite the limited direct effect, precipitation indirectly improved NPP by significantly increasing the SWC in 40–100 cm soil horizon. The latter not only directly enhanced NPP, but also indirectly promoted NPP by facilitating ET. In context of drought and water deficit, maintaining adequate soil moisture in the 40–100 cm layer through irrigation emerges as a potential strategy to ensure sustainable productivity. ET exerted the greatest comprehensive effect and the largest direct promotion on NPP. LAI, FAPAR, and SWC induced NPP variation indirectly through affecting ET. These consistently underscored the major relationship between productivity and water use. Future intensive agriculture in the NCP should prioritize the trade-off between carbon sequestration and water loss at plant physiological level. Improving the carbon sequestration per unit of water consumption through optimizing the photosynthesis-transpiration mechanism is an imperative climate-adaptative pathway for achieving sustainable food provision and mitigating water crisis.