Purpose of Review

Numerous studies have reported that treelines are moving to higher elevations and latitudes over the last few decades. Climate change is assumed to be the main driver behind the observed migration of treelines. Predicting how treelines are likely to move in the future is important to identify impacts on sensitive high-alpine ecosystems and help model potential climatic feedback mechanisms associated with the expansion of alpine and arctic forests.

Recent Findings

Here, we examine the correlation between treeline movements and recent climate change to better understand the drivers of treeline migration. Changes in monthly minimum and maximum temperature and precipitation between 1961 and 1970 and 2009 and 2018 for 256 treeline sites in the Northern Hemisphere were analysed through logistic regression modelling. The model was run at various spatial scales to assess if globally significant climatic drivers are applicable at regional scales.

Summary

Our analysis revealed that the rate of temperature change during the northern hemisphere autumn, particularly in October, was a significant predictor of treeline movement. At the end of the growing season, increased minimum temperatures corresponded with treeline migration. At warmer maximum summer temperatures, treelines were more likely to remain stationary. While statistically significant correlations were identified at global scales, there were also substantial regional correlations of treeline movement regarding warmer temperatures. Changes in precipitation correlated with treeline migration were not statistically significant. Continued warming is likely to further extend the growing season for alpine forests, promoting continued encroachment of forests into alpine grassland and tundra in areas where moisture availability does not present a limiting factor for tree survival.

中文翻译：

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北半球及次区域林线迁移与气温和降水变化关系的调查

审查目的

许多研究报告称，在过去的几十年里，林线正在向更高的海拔和纬度移动。气候变化被认为是观察到的林线迁移的主要驱动因素。预测林线未来可能如何移动对于确定对敏感高山生态系统的影响非常重要，并有助于模拟与高山和北极森林扩张相关的潜在气候反馈机制。

最近的发现

在这里，我们研究了林线移动与近期气候变化之间的相关性，以更好地了解林线迁移的驱动因素。通过逻辑回归模型分析了北半球256个林线地点1961年至1970年以及2009年至2018年的每月最低和最高气温以及降水量的变化。该模型在不同的空间尺度上运行，以评估全球重要的气候驱动因素是否适用于区域尺度。

概括

我们的分析表明，北半球秋季（尤其是十月）的温度变化率是林线移动的重要预测因素。在生长季节结束时，最低温度的增加与林线迁移相对应。在夏季最高气温升高的情况下，林线更有可能保持静止。虽然在全球范围内发现了统计上显着的相关性，但林线移动与气温升高也存在显着的区域相关性。与林线迁移相关的降水变化没有统计显着性。持续变暖可能会进一步延长高山森林的生长季节，促使森林继续侵蚀高山草原和苔原，而这些地区的水分供应不会成为树木生存的限制因素。