崇明东滩湿地芦苇和互花米草种群的分布格局及其与生境的相关性

摘要

应用GIS技术与实地调查相结合的方法,对上海崇明东滩湿地芦苇[Phragmites australis (Cav.) Trin.ex Steud.]和互花米草(Spartina alterniflora Loisel.)种群斑块的分布格局和沿潮位梯度的分布特征及其与部分环境参数的相关性进行了研究.结果显示:在1 500 m×100 m尺度内共有42个斑块;其中,互花米草种群斑块数量较少(13个)但面积和周长均较大,呈集中化分布特征;芦苇种群斑块数量最多(25个)但面积和周长均较小,呈现破碎化特征;芦苇种群的斑块密度和边缘密度均大于互花米草种群,但二者的聚集度指数及连通度指数均较高.沿潮位降低,芦苇种群数量减少,互花米草种群数量增多;中、低潮位以互花米草种群为主,中、高潮位以芦苇种群为主.不同潮位二者活体与立枯体株数有明显差异且具有不同程度的相关性,其中,互花米草总株数与芦苇活体株数、互花米草立枯体株数与芦苇立枯体株数均呈显著负相关(P＜0.05).该区域内各景观和斑块类型格局指数数值均较高,Shannon多样性和均匀性指数均较大.不同潮位的环境参数差异明显且与距堤坝的距离有不同程度的相关性;中潮位相对高程最高(9.2 m),低潮位土壤盐度最高(37.17 ng·L-1);随潮位降低土壤总氮和总磷含量总体上下降,但中高潮位土壤总磷含量最高、高潮位土壤总氮含量最高.芦苇活体株数与距堤坝的距离及土壤盐度、互花米草活体株数与相对高程及土壤总磷含量、互花米草总株数与相对高程均呈显著负相关(P＜0.05).研究结果揭示:该区域景观已出现破碎化现象;互花米草种群规模逐年增大,与芦苇种群有明显的竞争,二者呈明显的镶嵌分布格局.高潮位的相对高程低而土壤盐度高,这种微生境有利于互花米草生长却能抑制芦苇生长,对二者的扩散和分布格局产生复杂的局部性影响.%The patch distribution pattern and distribution characteristics along tidal level gradient of Phragmites australis (Cav.) Trin.ex Steud.and Spartina alterniflora Loisel.populations in Chongming Dongtan wetland of Shanghai and its correlation with some environmental parameters were studied by combined method of GIS technology with field investigation.The results show that there are forty-two patches in a scale of 1 500 m×100 m.In which, patch number of S.alterniflora population is less ( 13 patches) but patch area and circumference all are bigger, appearing the concentrated distributionrncharacteristics, while patch number of P.australis population is the most (25 patches) but patch area and circumference all are samller, appearing the fragmentation characteristics.And patch and edge densities of P.australis population are all higher than those of S.alterniflora population, but their aggregation and connectance indexes all are higher.With reducing of tidal level, number of P.australis population decreases and that of S.alterniflora population increases, and S.alterniflora population is the main in middle and low tidal levels while P.australis population is the main in middle and high tidal levels.There are obvious differences and correlations with different degrees in numbers of living plants and standing dead litters of two species in different tidal levels, in which, there are significantly negative correlations between total number of S.alterniflora individuals and number of living plants of P.australis , and between number of standing dead litters of S.alterniflora and that of P.australis ( P< 0.05).In this region, all of pattern parameter values of landscape and patch type are higher, and Shannon' s diversity and evenness indexes also are higher.There are obvious differences in environmental parameters in different tidal levels and environmental parameters are correlated with the distance to dam at different degrees.Relative elevation in middle tidal level is the highest (9.2 m) and soil salinity in low tidal level is the highest (37.17 ng · L-1 ).And with reducing of tidal levels, contents of total nitrogen and total phosphorus in soil decrease generally, but total phosphorus content in soil is the highest in middle-high tidal level and total nitrogen content in soil is the highest in high tidal level.There are significantly negative correlations between number of living plants of P.australis with the distance to dam or soil salinity, between number of living plants of S.alterniflora with relative elevation or total phosphorus content in soil, and between total number of S.alterniflora individuals with relative elevation (P < 0.05 ).It is suggested that there is fragmentation phenomenon of landscape in this region.Population size of S.alterniflora increases year by year and appears obvious competition with P.australis population, and two populations appear obvious mosaic distribution characteristics.Because of low relative elevation and high soil salinity in high tidal level, such microhabitat is beneficial to growth of 5.alterniflora but inhibit to growth of P.australis, thus may produce complicated locality influence on spread and distribution pattern of two populations.