[Discussion on the ecological theory and assessment methods of ecosystem quality and its evolution].

Ecological civilization construction and ecological environment governance are basic tasks of state gover-nance in China. China has clearly put forward the goal of improving ecosystem quality and stability. However, there are no consensus on the scientific concept of ecosystem quality and the assessment methods of ecosystem quality evolution, which has puzzled the academic community. Based on the summarization of the scientific concept of ecosystem quality and its evolution, we discussed the concept of ecosystem quality and its ecological theory basis by referencing the concept of production quality, quality management and quality assessment of material production. The scientific connotation of ecosystem quality and its evolution was discussed from the perspectives of ecosystem natural attribute-social attribute-economic attribute and the relationships between them, the cascade relations of ecosystem component-structure-process-function-service-efficacy, the feedback of factor-system-environment, and the logic relation of state ecosystem fluctuation-quantity variation-quality alternation. We proposed perspectives and approaches of multi-objective assessment of ecosystem quality alternation from the aspects of natural resource environment system, typical ecosystem, regional macro-ecosystem, and ecological engineering efficacy.