Response of Siberian treeline forests to historical and present climate changes - a (paleo)genetic approach

预计环北极的北方树木线将进一步向北移动，以应对预期的高纬度强烈变暖。这一过程可能会对气候产生巨大影响--由于植被的变化--气候反馈--并对生物多样性产生巨大影响。冻原生态系统的减少和森林面积的增加将导致物种和种内基因型生物多样性的重大变化。到目前为止，树木线的变化没有得到充分的记录或理解，特别是在西伯利亚，那里大约有一半的全球环北极北方树木线位于落叶松（落叶松）。目前还不确定（A）落叶松林能以多快的速度定殖新的区域（迁移速度），（B）补充和扩散的空间模式（迁移模式），以及（C）在气候变化时期，落叶松种和基因型之间的竞争如何影响落叶松林（竞争效应）。为了解决这些问题，该项目提出了一个多学科的计划，在十年尺度（在过去的400年）和整个全新世在西伯利亚东北部研究北极树线动态。北极-北方的树线在全新世期间经历了多个时期的树线波动，将对这些波动进行分析。该项目将孢粉学和树木年代学调查与沉积古DNA分析相结合。迄今为止，沉积古DNA的使用主要限于物种鉴定，但遗传数据也可能用于解决单个物种的时间动态。在本项目中，将分析泰梅尔半岛南部的湖泊沉积物岩心。特别是，将追求以下研究目标：1）迁移速度：将使用孢粉学和遗传学数据来推断树线的位置并确定对气候变化的反应速度，以确定落叶松的发生。 2)迁移模式：定殖树线种群的种内基因型将在树线推进的时候确定，并与当前的基因型分布进行比较，以分析招募是本地的还是通过长距离扩散。3)竞争效应：将确定造林后落叶松种和基因型发生的可能变化，以分析种间和种内竞争是否影响森林组成。这些历史过程的分析，在一个subspecific分辨率将提高我们的树线变化和相关的多样性变化的理解，并将能够更好地预测未来的变化。

The circum-arctic boreal treeline is projected to move further north in response to the prospected strong high-latitude warming. This process will potentially have tremendous effects on climate - due to changes in vegetation-climate feedbacks - and on biodiversity. The reduction of tundra ecosystems and the increase of forested areas will lead to significant changes in biodiversity, both at the level of species and of intraspecific genotypes. To date, the treeline changes are not sufficiently documented or understood, especially in Siberia, where about half of the global circum-arctic boreal treeline is located and dominated by larch (Larix). It is uncertain (A) how fast Larix forest can colonize new areas (migration speed), (B) which are the spatial patterns of recruitment and spread (migration pattern), and (C) how competition between Larix species and genotypes affects larch forests in times of climatic change (competition effects). To address these questions this project proposes a multidisciplinary program to study arctic treeline dynamics at the decadal scale (within the last 400 years) and throughout the Holocene in North-Eastern Siberia. The arctic-boreal treeline has experienced multiple periods of treeline fluctuations during the Holocene, and these will be analysed. The project combines the use of palynological and dendrochronological investigations with sedimentary ancient DNA analyses. The use of sedimentary ancient DNA has to date mostly been restricted to species identification, but genetic data can also potentially be used to address temporal dynamics within single species. In this project, lake sediment cores from the southern Taymyr peninsula will be analyzed. In particular, the following research objectives will be pursued: 1) Migration speed: The occurrence of Larix will be determined using palynological and genetic data to infer the position of the treeline and determine the speed of response to climatic changes. 2) Migration pattern: Intraspecific genotypes of colonizing treeline populations will be determined in times of treeline advance, and compared to the current genotype distribution, to analyze whether recruitment is local or by long distance dispersal. 3) Competition effects: Possible shifts in the occurrence of Larix species and genotypes after forestation will be determined to analyze whether inter- and intraspecific competition influences forest composition. The analysis of these historical processes at a subspecific resolution will improve our understanding of treeline shifts and associated diversity changes, and will enable better projections of future shifts.