Dynamic assessment of agri-ecological system based on emergy analysis in Yan'an City

The paper analyzed the input-output structure and emergy indexes of the agri-ecological system in Yan'an city by using the theory and method of emergy analysis.Such conclusions were reached:(1) The majority of emergy input is renewable emergy,and the overall emergy input shows ascendant trend;emergy output mainly includes crop cultivation and stock raising,but forestry and fish culture takes low percentage.(2) Renewable emergy ratio is high,but environment load rate is low,so the regional environment endures increasing pressure.(3) Emergy input rate and emergy utilizing rate are rising,on the contrary,emergy output rate and emergy currency ratio are reducing.Overall economic development level is low,but with the implementation of the western development and economic and technological progress,economic development speed is improving.(4) Dominance index of agricultural production is low,and system production advantage is not obvious;the system has high stability index,and the self-stability is strong;Agricultural sustainable development emergy index has greatly reduced,and sustainable development ability is enhanced.