Study on the Trade-Off Synergy Relationship of "Production-Living-Ecological" Functions in Chinese Counties: A Case Study of Chongqing Municipality

The trade-off and coordinated development of the "production-living-ecological" functions (PLEFs) of an area is an important basis for the optimization of the spatial pattern of the land, and helps to promote the harmonious symbiotic relationship between human beings and nature. This paper combines ecological niche theory, a coupling coordination model, and a trade-off synergy model to construct an evaluation index system for Chinese county PLEFs. Quantitative methods were used to measure spatiotemporal evolution characteristics, trade-off synergy of PLEFs in 38 counties in Chongqing, China, and the coupling coordination degree between PLEFs. The results showed that the ecological niche width of the "production-ecological" function revealed an overall growth trend. However, there was a mismatch in regional development of the "production-ecological" function, showing dislocation characteristics of "high in the west and low in the east" and "high in the east and low in the west." The niche width of the life function is similar to the comprehensive niche width of PLEFs, showing the characteristics of fluctuation and partition change. PLEFs and both the aforementioned functions showed distribution characteristics of "high in the west and low in the east," with the whole moving towards the stage of coordinated coupling, of which the "production-living" function has the highest coupling level. The functional coupling coordination degree of "production-living-ecological" is generally manifested as "high in the west and low in the east," and changing from the primary stage of imbalance to well-coordinated development. The "production-ecological" and "living-ecological" functions are in low-level imbalance in the primary and moderate coordination stages. Additionally, the evolution trend of the "production-ecological" and the "living-ecological" functions are similar, showing alternating and fluctuating development characteristics. Overall, in the past 20 years, Chongqing's "living-production" function has changed from a trade-off model to a collaborative development relationship, and the "living-ecological" function is generally based on a collaborative development relationship. The "ecological function" is manifested as a trade-off constraint relationship. Moreover, the coordinated development level of "living-production," "living-ecological," and "production-ecological" functions in the central urban area has been greatly improved, while counties have gradually shown different degrees of trade-offs.