Abstract: By the methods of emergy analysis, this paper studied the emergy flow in the ecological-economic system in Liaoning Province in 1990-2005, and the relationships between the environmental stress caused by resources’ input, output and consumption and the sustainable development of the Province. The results showed that in Liaoning Province, the nonrenewable resources occupied over 74% of the total consumed emergy, and the realistic population in 2005 was 3.26 times higher than the supportable population. In 1990-2005, the emergy yield ratio decreased from 65.40 to 10.13, emergy loading ratio increased from 2.72 to 7.18, and emergy sustainable index decreased from 24.03 to 1.41. The rapid economic growth in Liaoning Province was chiefly supported by the consumption of vast non-renewable resources, which caused the pressure of economic development on ecosystem getting more and more intense, the economic development increasingly depending on exogenous resources, and the sustainable development of Liaoning ecological-economic system having a continuing decrease. To realize the sustainable development in Liaoning Province, the principles of reduction, reutilization and recycling should be taken as the guidelines for promoting the reuse of wastes and the closed fine circulation of resources to minimize the discharge of wastes.

Key words: niche overlap, nekton species, niche breadth, interspecific association