长白山岳桦上侵苔原带的分布格局及其环境驱动机制

The tundra of the Changbai Mountains is typical temperate alpine tundra in Northeast Asia. Tree species, Betula ermanii from birch-tundra ecotone has encroached the tundra ecosystem of the Changbai Mountains under climate warming, which threatened the survival of indigenous tundra species and therefore make the ecological security of mountains confront with unprecedented challenges. Based on B. ermanii expansion in tundra zone of Changbai Mountains, firstly, we study spatial distribution of B. ermanii in tundra zone during past two decades, analyze topographic characteristics of its distribution using high resolution remote sensing images and topographic data by remote sensing technology and spatial analysis method, and analyze the habitat characteristics of B. ermanii. Secondly, we determine the driving factors of B. ermanii expansion and reveal the mechanism of its distribution change in tundra zone by in situ control experiment simulated environment change on the growth of birch, such as climate warming and nitrogen deposition. Thirdly, we predict the distribution change of B. ermanii in tundra zone on a landscape and long time scale using dynamic vegetation model. Finally, the environmental driving mechanism of B. ermanii expansion in tundra zone of Changbai Mountains is illustrated, which would provide the scientific basis for the future change of tundra vegetation in Changbai Mountains and have important significance for revealing the change of vegetation distribution in tundra and its response to global climate change.

长白山苔原是亚洲东北部最为典型的山地苔原。目前，在气候变暖的背景下，长白山岳桦林-苔原过渡带的乔木植物岳桦（Betula ermanii）逐渐侵入苔原生态系统，威胁本地苔原植物的生存，山地的生态安全面临前所未有的挑战。基于长白山苔原带岳桦的上侵现象，通过高分辨率遥感影像和地形数据，利用遥感技术及空间分析方法，研究近20a长白山苔原带岳桦的空间分布变化及其分布的地形特征，进一步分析岳桦分布的生境特征；通过野外原位控制实验模拟环境变化（气候变暖和氮沉降）对岳桦生长的影响，明确岳桦上侵苔原带的驱动因子，揭示长白山苔原带岳桦分布变化的机理；利用植被动态过程模型，在景观和长时间尺度上预测苔原带岳桦的分布变化；最终阐明岳桦上侵长白山苔原带的环境驱动机制，为研究长白山苔原带未来植被变化提供科学依据，对揭示苔原带植被分布的变化及其对全球气候变化的响应具有重要意义。

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