长白山林线树种岳桦幼树叶功能型性状随海拔梯度的变化

通过研究沿不同海拔岳桦幼树叶功能型性状,揭示其对环境的响应机制.结果表明:①随海拔升高,岳桦叶面积(LA)逐渐降低,比叶重(LMA)增加,但LMA较高的可塑性指数表明其适应更依赖叶片的薄厚变化；②岳桦叶绿素含量随海拔升高而显著下降,但类胡萝卜素Car和Car/Chl显著升高,Chlb和Car/Chl表现出较高的可塑性指数,更倾向于吸收蓝紫光和保护光合器官；③岳桦叶氮含量(Narea和Nmass)在海拔1800-1900m间最低,在低海拔和高海拔均表现较高,但Chl/Nmass却随海拔升高而显著增加,Nmasss比Narea具有较高的可塑性指数,对光能的吸收更依赖Nmass对Chl的贡献,高海拔主要将更多的氮投资于光合器官的保护(1900m以上),低海拔则更倾向于光合生产(1800m以下)；④随海拔升高,MDA增加,但随之抗氧化物质DS、Pro和APX活性增加,负责对活性氧的抵御和清除,但APX活性最大的可塑性指数表明活性氧的清除更依赖于酶促系统,但在海拔1900m以上,APX活性差异不显著,生理抗性逐渐下降,限制岳桦继续向高海拔生长；⑤抗氧化物质可塑性指数最高,叶绿素和叶形态次之,叶氮最低,表明随海拔升高,岳桦林以保护自身的生存为最主要的适应策略机制,然后以增加吸收光能的Chlb及LMA指标为主要生长策略.

Response of leaf functional traits of Betula ermanii saplings to the altitudinal Variation

This study focuses on the leaf functional traits of Betula ermanii saplings along the altitude gradient of Changbai Mountain, a Natural Nature Reserve of China, and tries to reveal its environmental response mechanism. The main results are as follows: (1)As altitude increased, the leaf area (LA) of B.ermanii dropped significantly, while leaf dry mass per area (LMA) increased. But it also indicated that it more resorted to leaf thickness changing in the procedure of adaption due to a higher LMA plasticity index. (2)The content of Chlorophyll (Chla, Chlb andChla+b) of B.ermanii reduced as altitude climbing up, while carotenoids (Car) and the ratio of Car to Chla+b(Car/Chl) was just the opposite. A higher Chlb and Car/Chl plasticity index of B.ermanii suggested that it tended to assimilate ultraviolet-blue light and protect photosynthetic organs. (3)The content of Leaf nitrogen (N_area and N_mass) of B.ermanii was the least at altitude 1800-1900m, but was higher at the low and high altitude. However Chl/N_mass increased with height ascending. And absorption of light energy more relied on the contribution of nitrogen to Chl for a higher N_mass plasticity value in order to allocate more nitrogen into chemical defense in higher latitude(1900m above), and photosynthesis in lower latitude(1800m below). (4)With altitude increased, when the growth of B.ermanii was limited by the peroxide (such as MDA), antioxidant DS, Pro and APX activity adaptively increased, which was responsible for resisting and clearing reactive oxygen. The highest APX plasticity index of B.ermanii showed it more relied on enzymatic system to accomplish this process, But APX activity had no significant difference above 1900m, which meant that the physiological resistance decreased gradually, and a higher elevation may limit its distribution.(5)With elevation climbed up, B. ermanii took its own survival as the main policy mechanism due to the highest average plasticity index, and then took Chlb and LMA to absorb light energy as the main growth strategy with a higher plasticity index.