三峡库区一级支流渠溪河河口消落带优势植物生态位特征

Niche characteristics of dominant plants in the fluctuating zone of Quxi River estuary,the first reach of the Three Gorges Reservoir Area

为了揭示三峡水库消落带优势植物对环境的适应能力和种间关系,以三峡水库中、上段过渡区一级支流渠溪河河口附近消落带植物为研究对象,在参考相邻格子法对研究区样地样方调查基础上,采用生态位宽度和生态位重叠指标对优势植物生态位特征进行了分析。结果表明,优势物种狗牙根(Cynodon dactylon)、鬼针草(Bidens pilosa)、苍耳(Xanthium sibiricum)、稗(Echinochloa crusgalli)、空心莲子草(Alternanthera philoxeroides)、马唐(Digitaria sanguinalis)作为泛化种占总物种数的37.50%,具有分布范围较广、适应能力较强的特点,可作为三峡水库消落带植被恢复的先锋物种。干、支流消落带优势植物生态位重叠值>0.50的种对数分别为40、50,生态位重叠值为0的种对数分别为27、13,表明干流优势植物之间的竞争性相对弱于支流。渠溪河河口附近干、支流消落带优势植物之间多为不等宽生态位重叠,在一定程度上实现了生态位共用;少数植物之间呈现出分离生态位重叠,不参与竞争。优势植物生态位重叠具有干支流差异性和高程差异性。优势植物的泛化种与特化种区分与鉴定,对丰富区域性物种组成与生态修复起至关重要的作用。

In order to reveal the adaptability of dominant plants to the environment and the interspecies relationship of the dominant plants in the Three Gorges Reservoir′s water-level-fluctuating zone,the primary tributary of the middle and upper transition zone of the Three Gorges Reservoir was taken as the research object. Based on the survey of sample plots in the study area,niche width and niche overlap indicators were used to analyze and discuss the niche characteristics of dominant plants. The results showed that the dominant species,Cynodon dactylon,Bidens pilosa,Xanthium sibiricum,Echinochloa crusgalli,Alternanthera philoxeroides,and Digitaria sanguinalisas generalized species accounted for 37.50% of the total number of species,which had the characteristics of wide distribution and strong adaptability. It can be used as a pioneer species for vegetation restoration in the hydro-fluctuating zone of the Three Gorges Reservoir. The number of species pairs of dominant plants in the dry and tributary water-level fluctuating zones with a niche overlap value> 0.5 was 40 and 50,respectively,and the number of species pairs with a niche overlap value of 0 was 27 and 13,respectively. The competitiveness between them was relatively weaker than that of the tributaries. The dominant plants in the dry and tributary water-level fluctuating zones near the estuary of the Quxi River mostly overlap in unequal-width niches,achieving niche sharing to a certain extent;a few plants had overlapping niches and do not participate in competition. The niche overlap of dominant plants had differences in trunk and tributaries and differences in elevation. The differentiation and identification of generalized species and specialized species of dominant plants play a vital role in enriching regional species composition and ecological restoration.