Fig 1.
The location of Yuxi City in Yunnan Province and China. The image was obtained by using ArcGIS 10.5.
Fig 2.
Pressure-support (PS) framework for cultivated land ecological security.
Broad arrow pointing down refers to the pressures on the cultivated land ecosystem and broad arrow pointing up refers to the support to the cultivated land ecosystem.
Table 1.
Eco-security evaluation indicators system of cultivated land.
Fig 3.
The BP neural network structure has 3 layers. Pi is the input data set, pj is the hidden layer node, a is the actual output, wij and wj are the weights.
Fig 4.
Optimizing weights and the threshold of the BP neural network by GA is divided into two steps. The first step used genetic algorithm embedding neural network and searched the best individual in the probable scope of the weights of BP network. The second step continued to apply BP neural network.
Table 2.
Grading standard for a cultivated land ecological security assessment in Yuxi City.
Table 3.
Land area proportions of different slope and topographic relief in counties.
Fig 5.
Spatial distributions of different slope and topographic relief in Yuxi city.
Natural break point method is adopted in classification on slopes and reliefs by using ArcGIS 10.5.
Table 4.
Land use/cover types of 2005 and 2015 in Yuxi City.
Fig 6.
Land use/cover change from 2005 to 2015 in Yuxi City.
The image of land use map is obtained by using ArcGIS 10.5.
Table 5.
Land use/cover conversion matrix from 2005 to 2015 in Yuxi City (hm2).
Fig 7.
Spatial change in land use/cover in Yuxi City from 2005 to 2015.
There are transferred-out areas in (a) and transferred-in areas in (b). Different colors refer to different change types.
Table 6.
Change of cultivated land ecological security from 2005 to 2015 in Yuxi City.
Fig 8.
Variation trends of ecological security of different counties.
Three broken lines refer to the changes of eco-pressure, eco-support and eco-security states of every county in Yuxi City respectively.