Threshold effects of vegetation cover on production-living-ecological functions coordination in Xiangyang City, China

Clarifying the nonlinear impacts of vegetation cover on production-living-ecological function (PLEF) coordination is essential to ecological restoration regulation and sustainable land use. However, the threshold effect of vegetation cover on PLEF coordination, particularly in major function-oriented zones (MFZs), has yet to receive attention. This study selected Xiangyang City, China, as the case area to identify the impact threshold of vegetation cover on PLEF coordination from the perspectives of the region as a whole and MFZ, respectively. The results showed that the PLEF coordination was high in the center and east while low in the west. For production-ecological function, 51.46% of the area was primarily coordinated and above, while for production-living function, 61.35% of the city area was severely uncoordinated. Vegetation cover was high in the west and low in the east. A negative correlation existed between vegetation cover and PLEF coordination. Urban built-up areas with lower vegetation cover showed higher levels of PLEF coordination, whereas western mountainous regions with higher vegetation cover demonstrated lower levels of PLEF coordination. Furthermore, vegetation cover exhibited a pronounced threshold effect on PLEF coordination, featuring conspicuous regional variations. The identified thresholds of vegetation cover for PLEF coordination in key development, agricultural production, and key ecological function zones were 0.3896, 0.2272, and 0.8161, respectively. Our study provides scientific references for the impact assessment of ecological restoration and the synergistic enhancement of land functions.