Spatial and Temporal Variations in the Ecological Vulnerability of Northern China

Table 1

Ecological vulnerability evaluation index system in northern China based on SRP model.

Target layer	Criterion layer	Basic index layer
Ecological sensitivity	Topographic factors	Elevation (+), slope (+), topographic fluctuation (+), river network density (-)
	Surface factor	Land use types (+)
	Soil factor	Soil erosion intensity (+)
	Meteorological factors	Average temperature (-), average precipitation (-)
Ecological resilience	Vegetation factors	Vegetation coverage (-), bioabundance index (-), net primary productivity (-)
Ecological pressure	Social factors	Population density (+), GDP per capita (+)

Note: +/- indicates forward indicators and negative indicators, respectively.