Coupling process of carbon sink service flow based on metacoupling framework

Carbon sink service (CSS) is crucial in addressing global warming and provides theoretical support for research on human‒system coupling. CSS generation, flow, and utilization in the composite ecosystem of mountains, rivers, forests, farmlands, lakes, and grasslands (CEMRFFLG) provides theoretical support for sustainable development. Quantifying the coupled supply‒flow‒demand processes and mechanisms of the CSS in CEMRFFLG remains a pressing issue for the study of carbon sink service flows (CSSFs). First, quantify the CSS supply and demand situation of CEMRFFLG Chongqing. Second, the coupling process of the CSSF among the water, forest, farmland, and grassland subsystems is explored via the breakpoint model combined with the metacoupling framework. Finally, a multiscenario simulation of CSSF was performed to reveal its flow mechanism. The results show that: (1) Net primary productivity (NPP) mainly comes from forests, and carbon emissions (CEs) mainly come from farmland. (2) During telecoupling, the forest subsystem has the highest total value in the outflow and inflow plots, accounting for 35.51% and 61.24% of the total, respectively. (3) The CSSF mainly moves from areas with forest areas to areas with human activities. This paper proposes optimization suggestions for the CSSF in Chongqing. This is essential for achieving the complex ecosystem's sustainable development.