升金湖浮游轮虫类型的组合与其生态因子

2006年10月对升金湖上湖,中湖和下湖10个断面27个采样点的调查,发现浮游轮虫14属39种。密度优势种为裂足臂尾轮虫(Branchionus schizocerca)、萼花臂尾轮虫(B.calyciflorus)、壶状臂尾轮虫(B.urceus)、月形单趾轮虫(Monostyla lunaris)、螺形龟甲轮虫(Keratella cochlearis)、双尖钩状狭甲轮虫(Colurella uncinata forma bicuspida-ta)、真足哈林轮虫(Harringia eupoda)。根据升金湖中轮虫所在分布区的生态因子,包括地理位置、海拔高度、年降水量、年积温、1月份平均温度、7月份平均温度、10月份平均温度及水体的理化性质,得出浮游轮虫类型组合的所指示的现代气候是中国东部地区温暖湿润气候,同时所指示的生态环境是中国东部地区水生生态系统,为轮虫类的现代地理分布格局提供了科学依据。

Density Dependence of a Dominant Species and the Effects on Community Diversity Maintainance

In order to test whether density dependence influences community diversity, a combination of manipulative experimentation and plot surveys were done using Cryptocarya concinna, a dominant species in subtropical evergreen forest. Twelve pairs of 1 m^2 seedling plots were built around 12 adults, and plots were treated monthly with either a fungicide or a control. The surviving proportion of C. concinna seedlings at different stages was calculated, and an analysis was conducted on the impact of fungicide on seedling survival and species richness. Correlation between relative abundance and community evenness at different ages was analyzed using plot surveys. The results showed that fungicide treatment decreased species richness of the seedling community by pro- moting the recruitment of common species. Furthermore, census of a 25 m radius around adult C. concinna trees confirmed that the density of saplings increased with distance from adults. Relative abundance of C. concinna decreased with increasing age, and decreasing C. concinna dominance resulted in an increase in community even- ness. To avoid the appearance of a single optimum population, the dominance of C. concinna decreased with age via density dependence, and subsequently improved community species diversity.