珙桐群落种内与种间竞争研究

Intraspecific and Interspecific Competition in Davidia involucrata (Davidiaceae) Community

采用Hegyi的单木竞争指数模型对卧龙自然保护区的珙桐群落种内与种间竞争强度进行定量分析,并讨论了不同竞争强度下珙桐的形态变化。结果表明珙桐受到的竞争强度随着林木径级的增大而逐渐减小,珙桐种内竞争较之与其伴生树种间的竞争剧烈;在群体水平上,珙桐种内与种间竞争强度顺序为珙桐种内>汶川钓樟>野核桃>灯台树>光叶珙桐>白楠>总状山矾>五裂槭>稠李>蛮青冈;竞争强度和对象木胸径的关系服从幂函数关系(CI=AD-B),当珙桐的胸径达到30cm以上时,竞争强度变化很小,所得的模型能很好的预测珙桐种内与种间的竞争强度;不同竞争强度下,珙桐主干各层的逐级分枝率(R12)、分枝角度、平均枝长和当年生枝条长都有一定的差异,其中下层的分枝角度、平均枝长和当年生枝条长对邻体竞争表现出极强的可塑性。说明珙桐通过自身形态变化,提高了对资源的利用能力,增强了对不同生境的适应性。

Davidia irwolucrata is a rare valuable and endangered plant in China. In order to study neighborhood competition effects, the intraspecific and interspecific competion intensity in Davidia irwolucrata community in Wolong Nature Reserve was analyzed quantitatively by using Hegyi individual tree competition index model. And the morphological characteristics of Davidia irwolucrata were investigated under different neighborhood competition intensity. The results showed that the competition intensity in Davidia involucrata decreased gradually with the increasing of forest tree dianreter class and the intraspecific competition in Davidia involucrata was more intensive than interspecific competition. The order of the intraspe- cific and intempecific competition intensity at the community level was： intraspecific 〉 Lindira pulcherrima 〉 Juglans cathayensis 〉 Conuts eontroversa 〉 Davidia involucrata var. vilmoriniana 〉 Phoebe neuramha 〉 Symplocos botryamha Franeh 〉 Acer oliverianum 〉 Prunus branchypoda 〉 Cyclobalanopsis oxyodon. The relationship between competition intensity and individual growth of objective tree closely followed the following equation： CI = AD^-B. The change in competition intensity is very small when the diameter of the objective tree reaches 30 cm. The model can stimulate and predict the intraspecific and interspecific competition efficeiently. The morphology of Davsidia involucrata, such as stepwise bifurcation ratio 1：2, branching angle, average branch and current-year branch lenghth of the main stem in different strata, was modified under different competition intensity. The plasticity of substrate branching angle, substrate average branch length and substrate currentyear branch length was very obvious in response to different neighborhood competion intensity. That suggests Davidia involucrata can improve its capacity to explore the resource and adapt to different habitats through morphological changes.