亚热带天然常绿阔叶林林下9种灌木细根形态和C、N化学计量特征

林下灌木是亚热带常绿阔叶林重要的构成部分,但林下灌木细根功能性状变异规律及地下生态策略仍不清楚。以福建建瓯万木林自然保护区内9种灌木为研究对象,对细根直径、根长、比根长、组织密度、碳浓度和氮浓度6个细根性状进行研究,采用序级划分法,分析不同树种细根性状序级间的变化特征、常绿和落叶灌木细根性状之间的差异,不同序级细根性状之间的关系以及细根性状变异维度。结果表明:树种和序级对9种灌木细根形态和化学性质有显著影响。直径、根长、根组织密度随着序级的增加而逐渐增加,比根长和氮浓度逐渐减小,碳浓度在序级间的变化趋势不一,未表现出明显的规律。落叶灌木细根直径、根长和氮浓度均显著高于常绿灌木,碳浓度和组织密度显著低于常绿灌木,表明与常绿灌木相比落叶灌木更偏向于资源获取型生态策略,常绿灌木则更偏向于保守型策略。灌木细根在不同序级间的直径与比根长、组织密度,氮浓度与组织密度有较强的相关性,细根其他性状间的关系并不密切或因序级而异。主成分分析结果表明灌木细根性状变异沿一个主成分轴发生变异,该轴表示灌木细根的资源获取和保守的权衡策略。

Morphology and C and N stoichiometry traits of fine roots of nine understory shrubs in subtropical natural evergreen broad-leaved forest

Undergrowth shrub is an important component of subtropical evergreen broad-leaved forest, but the variation of fine root functional traits and the underground ecological strategy of undergrowth shrubs are still unclear. In this study, the characteristics of fine root diameter, root length, specific root length, tissue density, carbon concentration and nitrogen concentration of nine shrubs in Wanmulin Nature Reserve of Jian ''ou, Fujian Province were studied. We analyzed the variation of the functional trait of fine roots in root orders, the difference between the root traits of evergreen and deciduous shrubs, and the correlation between the morphology and chemical characters of fine roots in different root orders. Then we used principal component analysis to explore the variation dimension of fine root functional traits. The results showed that tree species and orders had significant effects on the morphology and chemical properties of the fine roots of the nine shrubs. The root diameter, root length and tissue density increased gradually with the increase of the root order, the specific root length and nitrogen concentration decreased gradually. There is no consistent pattern of change in carbon concentration. The fine root diameter, root length and nitrogen concentration of the first order root of deciduous shrubs were higher than that of evergreen shrubs, and the carbon concentration and tissue density were lower than that of evergreen shrubs, indicating that deciduous shrubs were more inclined to resource acquisition strategy than evergreen shrubs, while evergreen shrubs were more inclined to conservative strategy. In this study, there was a strong correlation between root diameter, specific root length and tissue density. The relationship of nitrogen concentration and tissue density of fine root was also strong. The relationships between other characters of fine root were not close or differed between root orders. The principal component analysis results showed that the variation of shrub root traits varies along a principal component axis, which represents the trade-off between resource acquisition and conservation strategy of shrub roots.