扎龙湿地藻类优势种生态位及其种间联结性动态分析

为了解扎龙湿地藻类群落结构的季节特征和演替规律,对扎龙湿地藻类群落进行了分析,主要涉及藻类优势度、生态位、MFG功能群划分、生态位重叠值及联结系数分析。结果表明：(1)在检出的8门311种藻类中,夏季种类丰富度最高,全年优势种为狭形纤维藻和啮蚀隐藻。(2)优势种种类和密度季节性差异较大,春季以金藻-绿藻种类为主,夏季以绿藻-隐藻种类为主,秋季以隐藻-绿藻种类为主。(3)生态位宽度值与MFG功能群划分结合分析表明,优势种可分为3个大类别,不同种类对资源利用情况的差异较大,各季节广生态位种能较好的反映扎龙湿地水体环境的季节变化趋势。(4)生态位重叠值在不同季节上有较大差异,O_ik>0.6的占比分别为42.86%(春)、28.57%(夏)和25.00%(秋),表明春季优势种种间资源的竞争最为突出,种间竞争强于夏、秋两季。(5)种间联结性检验结果显示,扎龙湿地藻类优势种间总体联结上呈正关联关系,但是种间联结较为松散,种与种之间相对独立。研究表明,扎龙湿地藻类群落结构生态位测度均存在明显的季节波动,较好反映出水环境季节变化特征,可用来指示湿地水体环境的变化。

Dynamic analysis of niche and interspecific association of dominant algae species in Zhalong wetland

To better understand the annually structural changes and succession rules of algal communities, the algal communities was analyzed in Zhalong wetland, which involved the dominant algal group, niched width, MFG (Morpho-Functional Groups), niched overlap and connection coefficient. Results showed that the total of 311 species from 8 phyla were identified. The algal species richness was the highest in summer, and its dominant species in the whole year were Chlorella stenostis and Cryptophyllum rodentuma. The species and density of dominant species varied with spring (Chlorophyta sp. and Chrysophyta sp.), summer (Chlorophyta sp. and Cryptophyta sp.), and autumn (Cryptophyta sp. and Chlorophyta sp.), indicating that the water environments exhibited the seasonal fluctuation. The dominant algal species were divided into three large niche groups judged by niche width and MFG functional groups. The seasonal variation of dominant algal species reflected the fluctuation of wetland water environment, from "nutrient-poor shallow water type" in spring to "nutrient-poor mixed water type" in summer and "nutrient-neutral still water type" in autumn. The wide niche algal species in each season reflected the seasonal variations and could be used as ecological indicators for reflecting the Zhalong wetland water environments changes. The niched overlap values could reflect the competition between dominant species in different seasons, with the proportion of O_ik>0.6 was 42.86% (spring), 28.57% (summer) and 25.00% (autumn), respectively. The resource competition among dominant species was the most prominent in spring, with the species of Chrysospora sp. dominating. In summer, it reached a relatively stable state, with the dominant species such as Chlorophyta sp. dominating, and the competition of Cryptophyta sp. intensified in autumn.Interspecific association tests showed that the overall interspecific associated algae were positively correlated, but the algae in Zhalong wetland was relatively less. The results of variance ratio method showed that VR values were all greater than 1, indicating that there was a positive correlation between dominant species of algae communities under independent null hypothesis. Statistical W-value test results showed that the overall association of dominant algal species in Zhalong wetland was not significant in the three season, indicating that the overall association of dominant algal species in Zhalong wetland was loose and tended to be random, and the community structure was unstable due to the great influence of external disturbance on community stability. Based on the Chi-square test results of 18 dominant species throughout the year, only 4 pairs of 171 interspecific pairs were extremely significant positive associations, while the other pairs were not significant, which also indicated that the composition stability of dominant species in Zhalong wetland was poor, and the results of Jaccard index also confirmed this conclusion. The analysis indicated that the niched algal communities in Zhalong wetland exhibited obviously seasonal fluctuations, and could be adopted as the ecological indictors for reflecting the water environment variation in the wetland.