Treeline dynamics in Siberia under changing climates as inferred from an individual-based model for Larix, supplementary material@en

Siberian boreal forests are expected to expand northwards in the course of global warming. However, processes of the treeline ecotone transition, as well astiming and related climate feedbacks are still not understood. Here, we present 'Larix Vegetation Simulator' LAVESI, an individual-based spatially-explicit model that can simulate Larix gmelinii (RUPR.) RUPR. stand dynamics in an attempt to improve our understanding about past and future treeline movements under changing climates. The relevant processes (growth, seed production and dispersal, establishment and mortality) are incorporated and adjusted to observation data mainly gained from the literature. Results of a local sensitivity analysis support the robustness of the model's parameterization by giving relatively small sensitivity values. We tested the model by simulating tree stands under modern climate across the whole Taymyr Peninsula, north-central Siberia (c. 64-80° N; 92-119° E). We find tree densities similar to observed forests in the northern to mid-treeline areas, but densities are overestimated in the southern parts of the simulated region. Finally, from a temperature-forcing experiment, we detect that the responses of tree stands lag the hypothetical warming by several decades, until the end of 21st century. With our simulation experiments we demonstrate that the newly-developed model captures the dynamics of the Siberian latitudinal treeline.全球变暖背景下，西伯利亚寒温带针叶林预计将向北扩张。然而，林线交错带（treeline ecotone）的过渡过程、发生时序及其相关的气候反馈机制尚未得到充分解析。本研究提出一款名为兴安落叶松植被模拟器（Larix Vegetation Simulator, LAVESI）的模型，该模型属于基于个体的空间显式模型，可模拟兴安落叶松（Larix gmelinii (RUPR.) RUPR.）林分动态，以期深化我们对气候变化背景下林线历史与未来迁移过程的认知。该模型纳入了林木生长、种子生产与扩散、定居及死亡等关键过程，并依据主要来自文献的观测数据完成参数校准。局部敏感性分析结果显示模型敏感性数值相对较低，佐证了其参数化方案的鲁棒性。研究团队通过在西伯利亚中北部全泰梅尔半岛（约北纬64°~80°，东经92°~119°）范围内模拟现代气候下的林分，对该模型进行了验证。结果表明，林线北部至中部区域的模拟林木密度与实际观测森林的密度较为吻合，但模拟区域南部的林木密度存在高估现象。最后，通过温度强迫试验，我们发现林分对升温的响应相较于假设的变暖进程存在数十年的滞后，该滞后效应将持续至21世纪末。本研究通过系列模拟试验证实，这款新开发的模型能够准确捕捉西伯利亚纬度林线的动态变化。