Constraint effects among several key ecosystem service types and their influencing factors: A case study of the Pearl River Delta, China

Abstract

Identifying the multiscale relationships of ecosystem services (ESs) and their influencing factors is helpful for scientific decision-making and regional sustainable development. Different from previous studies on trade-off and synergy relationships, this paper introduced a new perspective of the constraint effect and reports a third type of service relationship. This paper first assessed four typical ESs in the Pearl River Delta region, including water conservation (WC), soil conservation (SC), habitat quality (HQ), and natural recreation (NR). Applying segmented quantile regression, constraint lines for scatter plots of NR and three other ESs were extracted on 8 scale series. The key features of constraint lines were analyzed, and the multiscale constraint effects of four types of environmental factors on ESs were identified. The results showed that (1) NR-SC and NR-WC had a hump-shaped constraint relationship, while NR-HQ had a linear constraint relationship. The NR service not only has an amplifier effect on the trade-off and synergy strength relationship of other services, but its threshold range is also an important reference for realizing a win–win situation; (2) The threshold and key characteristics of the constraint line are closely related to the maximum and range values of vegetation coverage, slope, and landscape diversity; (3) Environmental factors had five constraining effects on ESs: hump-shaped, positive convex, negative convex, U-shaped and exponential, which not only limited the upper boundary of the ES supply but also had lower boundary constraint effects on specific services; and (4) When the vegetation coverage reached 70 %, the average annual precipitation reached 2000 mm, and the landscape diversity reached approximately 0.4, the total amount of ESs approached the maximum value. When the slope is close to 7.5°, monitoring of vegetation and soil erosion needs to be strengthened to reduce ecological risks. The application of the constraint line method in analyzing complex influence relationships has been proven to visualize nonlinear relationships and quantify the optimal values of influencing factors. It will help maintain the long-term stability of the entire ecosystem and become an effective tool for multiscale regional ecological planning.