Abstract:

The system of evaluating ecological security of land in terms of pressure,state,and response is constructed based on PSR model.Then the entropy is used to evaluate the ecological security of land in Nan county from 2009 to 2013.The results show that the land ecological security in this county deteriorated from middle insecure to insecure.As for each subsystem,the pressure showed a gradual upward trend,but it still remained insecure；the state system and response system were all on a declining trend from insecure state to very insecure state.The main sub-system that influences the land ecological security is response.The influential factors include urbanization,grain output,application of chemical fertilizer,soil and water conservation,the proportion of the tertiary industry,investment in environmental protection,and industrial wastewater emission.

Key words: ecological security of land, evaluation, PSR model, entropy, Nan County