Table 2. Table of classification and grading indexes of environmental impact factors.

Environmental factor	Classification number	Classification index
Land use	15	paddy field, dry land, woodland, shrubbery, sparse woodland, other woodland, grassland, river channel, lake, reservoir pond, beach, urban land, rural homestead, other construction land, unused land
Soil	14	yellow brown soil, red clay, lime (rock) soil, purple soil, stone soil, coarse bone soil, tidal soil, paddy soil, red soil, yellow soil, urban area, lakes and reservoirs, rivers, others
Population (people)	15	58~176,176~253,253~322,322~388,388~460,460~548,548~672,672~865,865~1132, 1132~1606,1606~2247,2247~3178,3178~4557,4557~7369,>7369
Per capita GDP (Ten thousand)	15	0.11~0.57,0.57~0.82,0.82~0.95,0.95~1.06,1.06~1.18,1.18~1.34,1.34~1.49,1.49~ 1.64,1.64~1.89,1.89~2.23,2.23~2.64,2.64~3.30,3.30~4.78,4.78~7.89,>7.89
NDVI	15	0.108~0.423,0.423~0.487,0.487~0.545,0.545~0.598,0.598~0.642, 0.642~0.677,0.677~0.70,0.702~0.723,0.723~0.741,0.741~0.756, 0.756~0.770,0.770~0.786,0.786~0.803,0.803~0.825,>0.825
Precipitation (mm)	15	1197~1249,1249~1287,1287~1317,1317~1344,1344~1371,1371~1398, 1398~1423,1423~1449,1449~1474,1474~1496, 1496~1525,1525~1562,1562~1609,1609~1678,>1678
Temperature (°C)	15	9.7~13.6,13.6~16.0,16.0~16.9,16.9~17.5,17.5~17.7,17.7~17.9, 17.9~18.1,18.1~18.3,18.3~18.518.5~18.7,18.7~18.9, 18.9~19.1,19.1~19.3,19.3~19.5,>19.5
Altitude (m)	15	-2~56,56~84,84~113,113~147,147~182,182~216,216~248,248~284,284~335, 335~402,402~481,481~571,571~739,739~1022,>1022