垂直结构对桂西北干热河谷木本植物枝叶关系的影响

Effects of vertical structure on relationship between twigs and leaves of woody plants in the dry-hot valley of northwest Guangxi

【目的】探索桂西北干热河谷木本植物枝叶大小关系在垂直结构上的变化规律,为桂西北干热河谷地区植物保护及植被恢复提供理论依据。【方法】以广西雅长林场天然次生林群落为研究对象,采用单因素方差分析法、标准化主轴估计法和相关分析法,分析不同林层木本植物枝叶的性状大小差异、枝叶性状间的异速生长关系及相关关系。【结果】不同林层木本植物大部分枝叶性状存在显著差异(P<0.05,下同),随着林层的升高,枝条鲜质量、枝条干质量、小枝直径、总叶面积、叶片鲜质量、叶片干质量和叶片干物质含量均呈上升趋势,枝条相对含水量、分梢密度、单叶面积、叶片相对含水量和比叶面积均呈下降趋势。不同林层木本植物小枝横截面积与总叶面积均呈显著正向的异速生长关系,与分梢密度呈显著负向的异速生长关系,均存在共同斜率,且回归方程截距均存在显著差异,说明垂直结构变化未能改变木本植物枝条大小与枝条数量和叶面积的生物量权衡关系,但可显著改变枝叶性状资源配置比例,其中,高林层木本植物单位面积小枝上所支持的小枝数量更少,所支撑的总叶面积更多;相关分析结果表明,垂直结构变化对木本植物枝叶性状间相关性影响显著,相较于上层林,下层和中层林木本植物枝叶性状间的相关性更紧密。【结论】垂直结构变化未对木本植物枝叶性状间的权衡关系产生显著影响,但对枝叶的生物量配置方式影响显著,上层林木本植物单位面积小枝上具有更高的叶面积,而下层林木本植物单位面积枝条上所支撑的小枝数量更多,这是桂西北干热河谷木本植物适应异质环境所采取的生态策略。

[Objective]The present paper aimed to explore the changing law of twig and leaf size relationship in the vertical structure of wood-y plants in the dry-hot valley of northwest Guangxi,and provide a theoretical basis for plant protection and vegetation restoration in the dry-hot valley of northwest Guangxi.[Method]The natural secondary forest community in Yachang Forest Farm in the dry-hot valley of northwest Guangxi was studied by using one-way ANOVA,standardized principal axis estimation and correlation analysis to analyze the size diference allometric growth relationship and correlation relationship among twigs and leaves in diferent forest layers.[Result]There were significant differences in the traits of most twigs and leaves in different forest layers(P<0.05,the same as below).With the increase of forest layer,twig fresh weight,twig dry weight,twig diameter,total leaf area,leaf fresh weight,leaf dry weight and leaf dry mater content showed an increasing trend,while twig relative water content,branching intensity,individual leaf area,leaf relative water content and specific leaf area showed a de-creasing trend.There was a significant positive allometric growth relationship between twig cross-sectional area and total leaf area,and a sig-nificant negative allometric growth relationship between twig cross-sectional area and branching density in different forest layers,with a com-mon slope and significant differences in the intercept of the regression equation,indicating that vertical structure changes do not change the ecological tradeoff between branch size,branch number and leaf area,but significantly changed the proportion of resource allocation for twig and leaf traits.Tall forest plants supported fewer twigs per unit area and more total leaf area.Correlation analysis showed that vertical structure changes have a significant impact on plant twig and leaf traits,and the correlation between plant twig and leaf traits was closer in lower and middle forest than in upper forest.[Conclusion]Vertical structural changes do not significantly affect the ecological tradeoffs between leafy traits in woody plants,but significantly affect the biomass configuration of branches and leaves.The upper woody plants per unit area have a larger leaf area,while the lower woody plants support a larger number of branches,which is an ecological strategy adopted by woody plants in the dry-hot valley of northwest Guangxi.