三江平原湿地小叶章群落沿土壤水分梯度物种组成及多样性变化

Variations in plant species composition and diversity of Calamagrostis angustifolia community along soil water level gradient in the Sanjiang Plain

水分是影响湿地生态系统植物多样性的重要因素之一。以三江平原湿地小叶章群落为对象,研究了沿土壤水分梯度的典型草甸、沼泽化草甸和沼泽3种生境中群落物种组成及多样性特征。结果表明,3种生境均以小叶章占优势,但是伴生物种组成分化明显,其中,典型草甸指示种为二歧银莲花和垂梗繁缕,沼泽化草甸指示种为灰脉苔草和五脉山黧豆,沼泽指示种为漂筏苔草和毛果苔草;非度量多维尺度分析结果表明,草甸的物种组成差异更大,而沼泽和沼泽化草甸的物种组成差异较小。随土壤水分含量增加,小叶章的优势度逐渐降低,群落物种丰富度和Simpson优势度均呈逐渐降低的趋势,而Shannon-Wiener多样性与Pielou均匀度均呈逐渐上升的趋势;群落相似性系数(CJ、CS)呈现逐渐升高的趋势,二者的最大值分别出现在沼泽化草甸和沼泽,最小值分别出现在典型草甸和和沼泽化草甸,而Cody指数的变化格局呈现渐低的趋势,群落间共有物种数逐渐减少,物种替代速率降低。研究认为,三江平原小叶章湿地植物群落物种组成、Pielou均匀度、Simpson优势度和Shannon-Wiener多样性的变化格局与水分密切相关,β多样性的格局与水分联系紧密,物种丰富度的变化格局与水分无相关性,可能与物种自身的生物学特性以及其它环境因子有关,尚需进一步探讨。

Water is an important factor that affects the plant diversity of wetland ecosystems. It is also the main driving factor for wetland plant diversity and plant growth. The study of species diversity along the water environmental gradient in the context of global change is very important. The Sanjiang Plain is China＇s largest concentrated freshwater wetland distribution area and one of the key areas of China＇s five major freshwaters and wetlands. It is an important habitat for many rare and endangered animals, a breeding ground, and a migration route to many species. However, natural wetland areas are one of the fastest changing environments due to human activities worldwide. The area of Sanjiang Plain wetland has decreased, the groundwater level reduced, and the composition of plants significantly changed due to agricultural development-oriented human activities. We studied the species composition and diversity of three typical habitats, defined as typical meadow, wet meadow, and marsh, dominated by Calamagrostis angustifolia along the soil moisture gradient in Sanjiang Plain Wetlands. The results indicated that C. angustifolia was the dominant species in the three habitats, whereas the composition of associated species was significantly differentiated between the habitats. The typical indicator species of the meadow were Lathyrus quinquenervius and Carex orthostachys. The indicator species of the wet meadow were Carex pseudoconica and C. miyabei var. maopengensis. Non-metric multidimensional scaling analysis showed that the species composition was greater in meadow, and species composition was smaller in swamps and marsh meadow compared to other types of examined habitats. With soil moisture content increasing, the advantages of Calamagrostis angustifolia decreased and species richness and Simpson dominance showed a decreasing trend, while the Shannon-Wiener diversity and Pielou＇s evenness showed a gradual upward trend. The community similarity coefficient （CJ, CS） showed a gradual increasing trend, with the maximum values in marsh meadows and marshes, and the minimum values in typical meadow and marsh meadow. The change in Cody index pattern showed a gradual trend-the total number of species in communities was gradually reduced and the species turnover rate decreased. Studies suggest that plant species composition, Pielou＇s evenness index, Simpson＇s dominance index, and Shannon-Wiener diversity index of Calamagrostis angustifolia wetlands in Sanjiang Plain are closely related to changes in water dynamics. β diversity is closely related to the pattern of water gradient, whereas the change in species richness is not correlated with water gradient. This may be associated with the biological characteristics of species and other environmental factors, and warrants further studies.