非结构性碳水化合物（NSC）在高山岳桦林线形成机理中的指示意义

The formation mechanism of alpine treeline is always a hot issue and focus of climate change research. Non-structural carbohydrate (NSC) is the most important indicator in evaluating plant carbon budget, has been widely used in the research on formation mechanism of alpine treeline. However, recently the debates on the storage strategies of NSC in plant tissues has challenged the knowledge which derived from the past related studies. Therefore, that find out the effects of NSC in the process of alpine tree adapting to environment stress is the key to understand the treeline formation mechanism. Alpine Betula ermanii tree line, totally consists of one deciduous broadleaved tree species is the prime type on Northeast China, up to now, little study focus on the mechanism of resisting environmental stress for deciduous broadleaved tree species growing above treeline. This study will take alpine birch treeline on Changbai Mountain as an example, based on systematically field investigation, we study the seasonal dynamic and allocation of NSC and its components in birch tissues; combined with field simulation experiments and control experiments in green house, analyze the effects of low-temperature, drought and nutrient deficit on the concentration of NSC and its components, conversions among components and allocations among tree tissues, to figure out the indicating and regulating effects in the adaption mechanism of birch on the treeline. Finally, this study will make out the physiological mechanism of treeline formation, make up for the lack of related research, furthermore, provide theoretical support for predicting dynamic of treeline position under climate warming.

高山林线的形成机理一直是气候变化研究的热点。非结构性碳水化合物（NSC）是当前评价植物碳收支状况的主要量度指标，被广泛用于验证高山林线形成机理的研究。然而近年来对NSC储存策略的争论对以往大量研究结论的可信性提出了质疑。因此弄清NSC在高山树木对胁迫环境生理适应中的作用就成为了阐明高山林线形成机理的关键。高山岳桦林线是我国东北地区典型的由落叶阔叶树组成的林线，当前对林线上落叶阔叶树抗胁迫环境的生理机理研究得还很少。本项目选择长白山的高山岳桦林线为研究对象，通过系统的野外调查，研究NSC及其组分在岳桦组织中的季节动态和分配特征，并结合现地模拟实验和室内控制实验，研究低温、干旱和养分亏缺对岳桦组织中NSC及其组分的浓度、各组分的转换和在不同组织中分配等的影响，探讨NSC在林线树木生理适应机理中的指示意义和调控作用，揭示林线的形成机理，弥补相关研究的不足，进而为科学预测林线动态提供理论支持。

高山林线的形成机理一直是气候变化研究的热点。非结构性碳水化合物（NSCs）是当前评价植物碳收支状况的主要量度指标，被广泛用于验证高山林线形成机理的研究。然而近年来对NSC储存策略的争论对以往大量研究结论的可信性提出了质疑。因此弄清NSCs在高山树木对胁迫环境生理适应中的作用就成为了阐明高山林线形成机理的关键。基于此，本项目以长白山阔叶落叶林线树种岳桦为研究对象，结合野外和室内控制实验，系统研究了NSCs及其组分在岳桦不同组织器官中的季节动态和分配特征，及其与环境因子之间的关系。研究结果表明，（1）从组织器官功能差异和源汇控制（去叶）实验的角度都证实，岳桦可能存在主动存储过程即优先储存一定水平的NSCs，牺牲生长而保证树木在高海拔胁迫环境中的存活；（2）尽管以往研究报道高海拔植物的光合速率并未显著降低，但衡量整个生长季节的碳收支发现，随着海拔升高，岳桦根淀粉的累积程度持续下降，表明高山树木仍可能面临较高的碳亏缺风险；（3）此外，微环境对岳桦分布有显著影响，微环境可能通过影响热量等限制性环境因子，最终决定岳桦幼苗和幼树的定植和生长。因此，当前气候背景下，森林分布上限-林线树木的生长、分布除了受低温边界限制外，也受微地形的影响。气候变暖背景下，某种山地植物的分布区能否成功上移受物种对变化环境的适应性（可塑性）和微生境丰富度的共同影响。