武夷山常绿阔叶林木本植物小枝生物量分配

Twig biomass allocation of woody species in evergreen broad-leaf forest,Wuyi Mountain

小枝是木本植物的重要组成单元,研究其生物量分配策略有利于了解不同物种对环境的响应。本文以武夷山常绿阔叶林群落中19种木本植物的小枝为研究对象,采取标准化主轴回归(standardized major axis,SMA)的方法分析小枝的叶重、叶片面积、叶柄重、茎重、叶数量等性状特征,研究在群落水平上和不同生活型上,常绿阔叶林群落木本植物的小枝生物量分配格局。结果表明:群落水平上小枝重、总叶重和茎重三者间均呈等速生长关系。同样的,在乔木和灌木不同生活型分类中,茎重和总叶重也呈等速生长关系。但是,小枝重和总叶重、茎重之间的关系却不一致:小枝重和总叶重在乔木、灌木中分别呈等速生长关系和异速生长关系;小枝重和茎重在乔木、灌木中分别呈异速生长关系和等速生长关系;此外,单叶重和出叶强度在群落水平上呈负等速生长关系。然而,这种负等速生长关系并不存在于不同生活型的植物中。小枝水平上,总叶柄重和小枝重、总叶重均呈小于1的异速生长关系,即随叶的增大,小枝需要分配更多生物量用于运输组织和支撑结构(叶柄)的构建。因此,叶柄投资是限制亚热带常绿阔叶林当年生枝和叶增大的重要因素,对于小枝和叶大小的优化选择具有重要影响。

As twigs are important components of woody plants,studying the twig’s biomass allocation strategy is beneficial to understand the optimal growth strategies of plants. In this study,we sampled twigs from 19 woody species in an evergreen broad-leaf forest,Wuyi Mountain National Natural Reserve,Jiangxi,China. We analyzed the scaling relationships among twig’s leaf mass,leaf area,petiole mass,stem mass and leaf number of woody plants by standardized major axis（ SMA） to explore the biomass allocation patterns at community scale and synusia scale. Model Type II regression was used to determine the numerical values of scaling exponents and normalization constants of scaling relationships. Isometric relationships were found among the twig mass,total leaf mass and stem mass at the community scale. Stem mass and total leaf mass in the tree layer and shrub layer also showed invariant isometric scaling. In contrary,the twig mass showed allometric relationship with stem mass at tree layer,but showed isometric relationship at shrub layer. Additionally,negative isometric relationships were found between individual leaf mass and leafing intensity. The negative relationship between leafing intensity and individual leaf mass does not hold in different life forms of plant classification in the analysis. The total petiole mass scaled allometrically（ i.e.,α〈1.0） with respect to total leaf mass and twig mass on twig level,which indicated that twigs need to allocate more biomass for the construction of transport tissues and support structures with the increase of leaf mass. Therefore,the petiole investment plays a key role in limiting the growth of twigs and leaves,with important influence on the optimum selection of twig and leaf size.