近40年来山东省南四湖水生植被演变及其驱动因素

基于2019年南四湖水生植被调查结果,结合历史资料,分析了1983～2019年全湖水生植被演变情况。结果表明:1)近40年来,南四湖优势种数量下降,结构发生改变,耐污种菹草代替不耐污种轮叶黑藻、微齿眼子菜等成为优势种;2)物种丰富度急剧下降,由74种下降为16种;3)水生植被总面积大幅缩减,挺水植物面积减少93.7%;4)单位面积生物量减少,植被生产力降低。造成这种水生植被演变的主要因素包括:1)湖泊水位波动对植被生长影响显著,2002年的极度干旱压缩了水生植被的生存空间;2)湖泊营养水平变化诱发优势种演变更替;3)人类活动干扰水生植被的生长与分布等。建议控制湖区内不当的人类活动,更好地保护南四湖湿地生态系统的健康,促进水生植被的恢复。

Evolution Progress and Driving Factors for Aquatic Vegetation of Nansi Lake in Shandong Province over the Past 40 Years

Based on the exhaustive survey of vegetation in 2019 and the combination with historical data, the change in aquatic vegetation of Nansi Lake from 1983 to 2019 were analyzed. The results indicated that:1) In the past 40 years, the number of dominant species decreased and the community structure changed in Nansi Lake, Potamogeton crispus spread rapidly and the distribution area of species with high requirements for water quality were reduced. Dominant species were changed from Hydrilla verticillataandPotamogeton maackianus to Potamogeton crispus; 2) species richness of Nansi Lake has decreased from 74 species in 1983 to 26 species in 2010 and then to 16 species to 2019; 3) the total area of aquatic vegetation has decreased greatly from 1 180.8 km² in 1981 to 499.22 km² in 2015, emergent aquatic vegetation has decreased by 93.7%, floating plants has decreased by 92.4% from 1981 to 2015; 4) compared with the 1983, the biomass and vegetation productivity in unit area in 2015 decreased significantly. Such as biomass of aquatic vegetation has decreased by 63.7%. The main reasons for the change were following as:1) the amplitude, frequency, duration and regularity of water level fluctuations has a significant effect on the growth of aquatic vegetation, extreme drought in 2002 reduced the living space for aquatic vegetation; 2) the change of eutrophication status might as a turning point for succession of dominant species, habitat of aquatic vegetation were reduced by increasing nitrogen and phosphorus concentrations and deteriorating water quality; 3) in addition, human activities were also an important factor affecting the growth and distribution of aquatic vegetation in Nansi Lake. Human disturbances such as large-scale seine farming activities and unreasonable industrial and agricultural wastewater discharge worsen water quality, and caused degenerative progress of aquatic vegetation. To maintain the health of Nansi wetland ecosystem and promote the restoration of aquatic vegetation, it was suggested that the managers should take measures to reduce the interference of human activities on the growth of aquatic vegetation.