Constraint relationship of ecosystem services in the Yangtze River Economic Belt, China.

Understanding the relationship among ecosystem services (ESs) is essential to promote ESs management and sustainable development. The relationship between ESs is mutual and can be expressed in terms of trade-offs, synergy, and constraints. The paper selected the InVEST model to assess the water yield (WY), soil conservation (SC), food production (FP), net primary productivity (NPP), and habitat quality (HQ) of the Yangtze River Economic Belt (YREB) and used the constraint line method to analyze the relationship of paired ecological services at three scales: landscape, watershed, and land category. The following conclusions were drawn: (1) during the study period, the spatial changes of the five ecological services in the YREB did not change much, but the spatial distribution of the ecological services was different. (2) From 2000 to 2015, the constraint line of YREB paired ecological services had a high degree of fit. Under the three levels of landscape, watershed, and land category, the YREB has a variety of constraint types, including negative lines, logarithms, paraboloids, humped shapes, and rectangles. (3) At the three levels, the constraint lines between FP, NPP, WY, and SC and HQ were stable rectangular constraints; WY-SC was hump shaped, FP-NPP, FP-SC, FP-WY, NPP-WY, and NPP-SC changed with the scale, showing different spatial scale changes. (4) The paired ESs directly determined the ecological constraint curve but under the combined effect of other factors, which would affect or change the constraint line. We discussed the effects of weather, topography, and economy on the constraint relationship, and found that all have different degrees of influence.