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THE RELATIONSHIP BETWEEN REPRODUCTIVE ALLOCATION, FRUIT SET AND INDIVIDUAL SIZE OF CAMELLIA ROSTHORNIANA IN DIFFERENT COMMUNITIES

不同群落中川鄂连蕊茶的生殖分配与个体大小之间关系的探讨


研究了缙云山川鄂连蕊茶(Camellia rosthorniana)在3个群落类型中的生殖分配、生殖分配与个体大小之间的关系和座果率。结果表明:1)在地径1.0~3.5 cm范围内,种群间生殖分配差异显著,即毛竹林>针阔混交林>常绿阔叶林;在地径1.0~5.0 cm范围内,针阔混交林和常绿阔叶林之间差异不显著;在地径1.0~6.0 cm范围内,毛竹林显著高于针阔混交林和常绿阔叶林,而针阔混交林和常绿阔叶林之间差异不显著;因此种群间生殖分配比较时,应考虑种群间的大小分布。运用生殖分配的有关学说对川鄂连蕊茶生殖分配格局进行了解释,生境稳定性学说和生活史理论假说相结合可以解释川鄂连蕊茶生殖分配格局。2)川鄂连蕊茶个体生殖分配与个体大小之间存在抛物线关系。3)种群密度对川鄂连蕊茶座果率没有影响。

Camellia rosthorniana is a long-lived evergreen shrub, which is widely distributed in subtropical areas of China and occurs in many types of communities on Mt. Jinyun (29°50′ N, 106°26′ E). In the present study, reproductive allocation and fruit set (number of mature fruits/number of flower buds) of C. rosthorniana populations at three successional stages (Giant bamboo forest, mixed coniferous broadleaved forest and evergreen broadleaved forest) with different population structures and densities were compared. One 2 000 m2 plot was set up in each of the three C. rosthorniana populations. Field surveys showed that the basal diameters of the largest individuals of C. rosthorniana in the giant bamboo community, mixed coniferous broadleaved community and evergreen broadleaved community were 3.52, 5.37 and 6.44 cm, respectively. Population densities (Flowering plants) in the plots were 167, 222 and 621 for giant bamboo community, mixed coniferous broadleaved community and evergreen broadleaved community, respectively. It was also found that individuals of C. rosthorniana began to flower only after it reached a basal diameter of 1 cm. All individuals in the 1.0-1.5 cm (Basal diameter) size class in the giant bamboo community flowered, but only a proportion of individuals in the same size class flowered in the mixed coniferous broadleaved community and evergreen broadleaved community. Six reproductive individuals were randomly sampled from each size class (with 0.5cm as an interval) in each population. Reproductive allocation, based on annual production, was estimated for each size class and population. Fruit set was also estimated for each population from ten randomly selected reproductive individuals. Three hypotheses were evaluated with regard to the observed patterns of reproductive allocation. One hypothesis, that reproductive allocation patterns were a function of differences in resource availability, did not provide an explanation for our results. A second hypothesis, that reproductive allocation was negatively correlated with successional maturity of the habitat could explain the observed patterns of reproductive allocation but could not explain the differences in size structures of the three populations. The third, life history hypothesis which assumed the existence of a trade-off between current reproduction and vegetative growth and/or survival rate, could explain the differences in size structures among the three populations. Reproductive allocation increased monotonically within a range of basal area sizes only, and a parabolic, not linear, model could best delineate the relationship between reproductive allocation and plant size (indicated by basal diameter). No significant differences in fruit set among populations were detected.