鄱阳湖洲滩植被健康状态评价及其典型不健康年水文条件分析

在气候变化、人类活动的共同影响下,湿地生态系统退化的形势日益严峻。因此,开展浅水湖泊洲滩植被健康状态评价,探索导致湖泊洲滩植被结构和功能退化的原因具有十分重要的意义。通过构建逐层聚合的指标体系,运用综合健康指数法(EHCI)对鄱阳湖洲滩植被健康状态进行评价;并通过不健康年份湖泊水情与多年平均湖泊水情的对比,揭示对洲滩植物健康状态影响最为显著的湖泊水情。主要结论如下:(1)1989~2010年春季,鄱阳湖洲滩植被处于健康和亚健康状态的年份约占总体的80%,不健康年份约占总体的20%;同时段的秋季,鄱阳湖洲滩植被在健康和亚健康状态的年份约占总体的85%,不健康年份约占总体的15%。1989~2010年,鄱阳湖年均洲滩植被健康状态均在健康与亚健康之间,无不健康年份。鄱阳湖洲滩植被健康状态在年尺度上表现出比单一季节更好的稳定性。(2)涨水期水情是影响鄱阳湖春季洲滩植被健康状态的主要水文要素。1989~2010年春,鄱阳湖洲滩植被不健康年份发生在典型的春旱年份2005年和典型的春涝年份2010年。丰水期水情是影响鄱阳湖秋季洲滩植被健康状态的主要水文要素。1989~2010年秋,鄱阳湖洲滩植被不健康年份出现在典型的丰水期高水情年份1999年和典型的丰水期低水情年份2001年。就鄱阳湖年均水位波动状况而言,其具有比单一季节水位波动更好的稳定性,因此导致鄱阳湖洲滩植被全年的总体健康状态比单一季节具有更好的稳定性。本研究结果对于科学的认识鄱阳湖洲滩植被现状及其变化原因具有重要的现实意义,也为鄱阳湖洲滩湿地管理、生态修复及工程决策提供了重要的科学依据。

ECOSYSTEM HEALTH ASSESSMENT OF POYANG LAKE WETLAND AND THE ASSOCIATED HYDROLOGICAL CONDITIONS

Based on the Ecological Health Comprehensive Index (EHCI) method, wetland ecosystem health assessment was conducted in the Poyang Lake wetland. The assessment results showed that:(1) for the wetland in spring during 1989-2010, the percentages of ‘healthy’, ‘sub-healthy’ and ‘ill’ ecological situation were 40%, 40% and 20%,respectively. (2) For the wetland in autumn during 1989-2010, the percentages of ‘healthy’, ‘sub-healthy’ and ‘ill’ ecological situation were 38%,46% and 15%, respectively. (3) For the annual wetland state during 1989-2010 the percentages of ‘healthy’, ‘sub-healthy’ and ‘ill’ ecological situation were 57%,43% and 0%, respectively. Based on a thorough analysis of the hydrological regime in the ‘ill’ ecological years, we found that:(1) hydrological condition in the rising season was decisive for wetland vegetation in spring. The effect trend was that high lake level in rising season resulted in small coverage area of the whole wetland vegetation. However, low lake level in rising season resulted in expansion of reed belts and shrinkage of sedge belts. (2) Hydrological condition in the flood season was decisive for wetland vegetation in autumn. The effect trend was that high lake level in flood season resulted in large coverage area of sedge belts and small coverage area of reed belts, and vice versa. (3)The ecological situation of Poyang Lake wetland were more stable on the annual scale than that in the seasonal scale, which was mainly induced by the stability discrepancy of lake level fluctuations in the inter-year and that in the intra-year. The result of this study may have some implications for the ecosystem health assessment of other littoral wetland, especially for those surrounded by lakes with dramatic water level fluctuations.