On temporal and spatial evolution characteristics of ecological environment in upper reaches of the Minjiang River

The consolidation and expansion of ecological environment protection and construction in the Transitional geographical space of mountain area is of great significance to regional sustainable development and rural revitalization. The article, based on the "pressure-state-response" (PSR) model, constructs a comprehensive evaluation index system for the ecological environment in the upper reaches of the Minjiang River, and in combination with the analytic hierarchy process and entropy weight method, the state of ecological environment in 2000, 2005, 2010, 2015 and 2020 was subjected to a comprehensive evaluation. Of which the results were graded into a five-scale evaluation system:poor, rather poor, average, good and excellent, and the spatio-temporal evolution characteristics were studied by use of the hot- and cold-spot analytical tools. The findings are as follows:(1) In terms of time, the ecological environment in the upper reaches of the Minjiang River undergoes little change in general, showing a good trend on the whole; (2) On a grid scale, the spatial distribution difference of ecological environment status is obvious, yet the distribution characteristics are relatively stable. And its distribution takes on a strong spatial agglomeration. Poor and relatively poor districts were mainly distributed in the east and southeast of the study area, while the good and excellent regions were chiefly found in the northwest; (3) The ecological environment has strong spatial agglomeration; (4) The spatial distribution characteristics of cold- and hot- spots in ecological environment do not change significantly. The distribution of high value areas is scattered, and the low value areas mainly gather along both sides of the Minjiang River system.