黄河三角洲人工恢复芦苇湿地生态系统健康评价

Assessing the health of rehabilitated reed wetland ecosystem in the Yellow River Delta

研究目的是对黄河三角洲人工恢复芦苇湿地生态系统的健康状况进行评价。按照层次分析法的思想,从环境、植物群落和植物生理生化特征等3个方面构建评价指标体系。在专家意见的基础上,确定各个指标的权重,计算生态系统健康指数。通过与自然芦苇湿地对比,对人工恢复芦苇湿地的健康状况进行评价。结果显示:人工恢复芦苇湿地的土壤有机质、全氮和全盐含量、群落盖度、密度和地上生物量等指标显著低于自然芦苇湿地,地表水电导率、叶片的APX、DHAR、MDHAR等酶的活性显著高于自然芦苇湿地,其生态系统健康指数低于自然芦苇湿地。这说明在短时间内,人工恢复芦苇湿地的健康状况和自然芦苇湿地还存在一定差距。恢复时间对生态系统健康评价有重要影响,长时间尺度上监测数据的积累是全面、深入了解生态系统、评价生态系统健康状况所必需的。

The Yellow River Delta is a typical estuary wetland in Eastern China. In recent years, extensive agricultural and petroleum exploitation caused severe damage to the natural wetland ecosystem in the Yellow River Delta. To restore the wetland ecosystem, large areas of rehabilitated reed wetland were constructed in this region. However, few studies have investigated the effect of ecological restoration and assessed the health status of rehabilitated reed wetland in the Yellow River Delta. The objective of this study was to establish an evaluation index system based on the analytic hierarchy process （AHP） and assess the health status of the rehabilitated reed wetland in the Yellow River Delta.According to the principles of the AHP, we built an evaluation index system based on the characteristics of habitat （ pH and conductivity of surface water, soil salt content, soil organic matter content, and soil total nitrogen content ）, community structure （coverage, density, height, and aboveground biomass ）, and plant physiological and biochemical features （SOD, superoxide dismutase; APX, ascrobate peroxidase ; CAT, catalase ; GPX, guaiacol peroxidase ; DHAR, dehydroascorbate reductase ; MDHAR, monodehydroascorbate reductase）. The original data of the evaluation indexes were normalized and converted into data matrix to calculate the weight of each evaluation index based on expert knowledge and the AHP principles. The weights reflected the relative importance of the evaluation index. The weights and normalized evaluation index data were together used to calculate the ecosystem health index. The health status of rehabilitated wetland ecosystem was determined by a comparison between the rehabilitated and natural reed wetlands. From the result of the weight calculation, we found that aboveground biomass is the most important index among the 15 evaluation indexes, followed by coverage, density, soil organic matter content, soil total nitrogen content, the activities of SOD, CAT, GPX, soil salt content, surface water conductivity, and pH value. Through the comparison between rehabilitated and natural reed wetlands, we found that the soil organic matter content, soil total nitrogen content, soil salt content, density, and aboveground biomass of the rehabilitated reed wetland were significantly lower than those of the natural reed wetland. However, the electrical conductivity of surface water and the activities of APX, DHAR, and MDHAR of the rehabilitated reed wetland were significantly higher than those of the natural reed wetland. Thus, the result of the synthetic evaluation showed that the ecosystem health index of the rehabilitated reed wetland is lower than that of the natural reed wetland. The results indicated that the health status of rehabilitated reed wetland could not reach that of a natural reed wetland within a short period. Because recovery time has important influences on ecosystem health, long-term monitoring data is necessary for improved understanding of ecosystem dynamics and assessment of ecosystem health.