杭州湾滨海滩涂盐基阳离子对植物分布及多样性的影响

滨海滩涂由于其高含盐量显著影响了植物群落分布及生物多样性。目前有关滩涂含盐量与生物多样性的关系研究较多,但不同区域盐基离子组成不同,且对植物的影响也存在较大差异,以杭州湾南岸不同年代形成的滩涂为研究对象,系统监测了50个样方土壤交换性盐基阳离子的组成、分布和植物组成及多样性特征等,采用去趋势典范对应分析(DCCA)、线性回归和多元逐步回归分析了4种盐基阳离子对物种数量、分布和多样性的影响。结果表明,杭州湾南岸滩涂4种主要盐基阳离子含量(g/kg)大小顺序为Ca²⁺>Na⁺>Mg²⁺>K⁺,其中Ca²⁺占到总含量的61.97%;经DCCA分析发现4种盐基阳离子对植物群落的分布均有显著影响,但以Ca²⁺的影响程度最大;随着盐基离子含量的逐渐降低,物种数量逐渐增加,多样性指数逐渐增加,同时也发现Ca²⁺对两种多样性指数影响最大。

Effects of soil base cation composition on plant distribution and diversity in coastal wetlands of Hangzhou Bay, East China

There are 32 000 km of coastal line and 2×10⁶ hm² of beach land in coastal area, China. Hangzhou Bay coastal wetland is the intersection of north and south coastal wetlands in China, and which is implied that the research is of high value in the view of science. It is well known that plant distribution and bio-diversity are influenced strongly by soil salinity of beach in coastal wetlands. Relationships between plant species distribution, bio-diversity and soil salinity have been studied in many sites in past several decades, yet few focusing on soil base cations composition of beach and their effects on plant distribution and diversity. In this paper, soil base cations composition and distribution, plant species composition and diversity in 50 plots were monitored using method of line transects with random sampling in Hangzhou Bay coastal wetlands, and the effects of base cations on plant species distribution and diversity were analyzed using Detrended Canonical Correspondence Analysis (DCCA), stepwise regression and linear regression. The 4 main base cations concentrations (means ± SD) were (3.66±1.58) g/kg (Ca²⁺), (1.83±1.25) g/kg (Na⁺), (0.56±0.23) g/kg (Mg²⁺), (0.22±0.12) g/kg (K⁺), respectively. And the concentration of Ca²⁺ was accounted for 61.97% of total base cations concentrations. While the base cations concentrations of coastal beach out of inning dam ((4.87±0.41), (2.19±0.26), (0.65±0.12), (0.28±0.07) g/kg, respectively) were higher than in inning dam (P<0.05). Meanwhile, 17 species were found in 50 plots, herbs mainly including typical beach plants, such as Scirpus mariqueter, Phragmites communis, Spartina alterniflora, etc., and shrubs including Tamarix chinensis and Salix matsudana. The DCCA axis 1, explained 59% of variance of species and environment relation and showed significant relationships to 4 base cations, reflected the gradient of 4 base cations, which meant they all influenced plant distribution. While Ca²⁺, owned longest axis and smallest angle, was the most important factors. The DCCA axis 2, explained 25% of variance of species and environment relation, reflected the gradient of Mg²⁺ and K⁺. And we found the number of plant species decreased with the increasing of both DCCA axis 1 and DCCA axis 2. With the decreasing of base cations concentrations of plots, the values of diversity indices, both Shannon-Wiener index (H') and Simpson index (DS), increased. Moreover, significantly relationships were found between 4 base cations concentrations and H', DS (P<0.05). Hereafter, only Ca²⁺ was selected through stepwise regression, which indicated the importance of Ca²⁺ on plant diversity. The results may mean that calcium ion, with highest concentration on the beach, had most important effect on plant distribution and diversity in Hangzhou Bay coastal wetlands, which is different to other beach wetlands in China.