鄱阳湖洲滩湿地地下水位对灰化薹草种群的影响

在气候变化和人类活动的双重影响下,近年来鄱阳湖流域极端水文事件频发,洲滩湿地生态过程也相应发生变化,开展鄱阳湖水文过程变化与植被演替过程的交互作用研究十分必要。选择鄱阳湖典型洲滩植物灰化薹草(Carex cinerascens)为研究对象,通过地下水位控制模拟试验,设置地下水位埋深10、20、40、80、120cm等5个处理,系统探讨了地下水位埋深对鄱阳湖典型湿地植物灰化薹草生长与种群演变的影响。研究结果表明:春季,不同地下水位对灰化薹草种群的密度和群落多样性影响不显著;夏季,不同地下水位对灰化薹草的密度、种群多样性以及藜蒿和灰化薹草的高度比影响显著。地下水位埋深10cm更适宜灰化薹草植株的生长与群落结构的稳定,而地下水位埋深低于80cm,尤其是低于120cm可能会导致灰化薹草种群的退化与演替。研究结果对于揭示地下水位波动作用下鄱阳湖湿地植被种群发生的短期变化和长期演变趋势具有重要的指示意义。

Response of Carex cinerascens populations to groundwater level gradients in the Poyang Lake wetland

Poyang Lake has faced frequent extreme events such as floods and droughts owing to climate change and human activities. These changes in hydrological processes directly impact the ecological processes of the Poyang Lake wetland. Therefore, it is essential to investigate the relationship between hydrological processes and vegetation succession in Poyang Lake. In this study, the influence of groundwater on the development of Carex cinerascens populations was studied by controlled experiments. C. cinerascens, one of the dominant species in the Poyang Lake wetland, was planted at five groundwater level gradients (-10, -20, -40, -80, and -120 cm relative to the soil surface). The number of C. cinerascens plants per barrel was surveyed and recorded at approximately 15-day intervals. The soil water content decreased significantly with decreasing groundwater level, though there was no difference in water content between the -80 cm and -120 cm groundwater level treatments. The groundwater level gradient did not significantly affect the characteristics of the C. cinerascens population in the spring. However, the density, growth form, diversity, and the relative heights of Artemisia selengensis and C. cinerascens showed significant differences between treatments in the summer. The density for the five groundwater levels exhibited similar changes; it decreased significantly with decreasing groundwater level. Plants in the -80 cm and -120 cm levels exhibited decreases in growth earlier than plants in the other three groundwater treatments. The Simpson diversity index for the -120 cm groundwater level treatment was significantly higher than that observed for the -10 cm, -20 cm, and -40 cm treatments. The height ratio of A. selengensis to C. cinerascens in the -10 cm groundwater level treatment was always less than 0.9, which was far smaller than the ratios observed for other groundwater treatments. At the end of the experiment, the height ratios in -80 cm and -120 cm treatments were 4.7 and 4.5 times greater than that of the -10 cm groundwater treatment. A groundwater level of -10 cm was advantageous with respect to the growth and stability of the C. cinerascens population compared with the other treatments, and a groundwater level of -80 cm can cause degradation and succession of C. cinerascens populations. When the groundwater level was below -120 cm, this effect is maximal. The results and findings in this paper are helpful to assess the effects of groundwater level fluctuation on the short-term changes and long-term succession of typical vegetation under changing groundwater level conditions in Poyang Lake wetlands.