Abstract: Based on the investigations in the Zhifanggou Watershed of Loess hilly and gully region from 1938 to 2007, and the establishment of eco-environmental and socio-economic comprehensive evaluation indices and coupling model, this paper analyzed the coupling situation of the agriculture-ecology-economic system in the watershed. During the study period, the agriculture-ecology-economic system in the watershed had gone through the coupling processes of economic system vs. ecosystem initial regenesis-consumption-promotion-coordination, and of ecosystem vs. economic system primary response-lag behind-recovery-coordination. According to the coupling degree fitting curves and the coupling type classification, the current agriculture-ecology-economic system in the watershed was still in the situation of coupling, and would be well coordinated.

Key words: Zhifanggou Watershed, agriculture-ecology-economic system, coupling model, coupling type, coupling situation, straw amendment, C/N, soil CO₂ emission, black soil, soil carbon sequestration.