Abstract
Treeline shift and tree growth often respond to climatic changes and it is critical to identify and quantify their dynamics. Some regions are particularly sensitive to climate change and the Altai Mountains, located in Central and East Asia, are showing unequivocal signs. The mean annual temperature in the area has increased by 1.3–1.7 °C in the last century. As this mountain range has ancient and protected forests on alpine slopes, we focus on determining the treeline structure and dynamics. We integrated in situ fine-scale allometric data with analyses from dendrochronological samples, high-resolution 3D drone photos and new satellite images to study the dynamics and underlying causal mechanisms of any treeline movement and growth changes in a remote preserved forest at the Aktru Research Station in the Altai Mountain. We show that temperature increase has a negative effect on mountain tree growth. In contrast, only younger trees grow at higher altitudes and we document a relatively fast upward shift of the treeline. During the last 52 years, treeline moved about 150 m upward and the rate of movement accelerated until recently. Before the 1950s, it never shifted over 2150–2200 m a.s.l. We suggest that a continuous upward expansion of the treeline would be at the expense of meadow and shrub species and radically change this high-mountain ecosystem with its endemic flora. This documented treeline shift represents clear evidence of the increased velocity of climate change during the last century.
Highlights
IntroductionPlanet Earth has experienced significant temperature increases, in the Northern Hemisphere[1,2]
Over the last century, planet Earth has experienced significant temperature increases, in the Northern Hemisphere[1,2]
These studies in the Tianshan and Altai Mountains and in other high-mountains of the world[40,41], showed that climate change might have a harmful effect on tree growth and recent evidence reported that the lower forests can display “browning” over extensive areas in the boreal region[42]
Summary
Planet Earth has experienced significant temperature increases, in the Northern Hemisphere[1,2]. Www.nature.com/scientificreports annual temperature in the Northern Altai Mountains has shown a significant increase of 1.3–1.7 °C in the last century[30] This general trend was confirmed by a comprehensive study that analyzed 50 years of temperature and precipitation variations in the whole mountain chain in both Russia and China[31]. Several studies reconstructed the impact of climate change in the Central Eurasia from tree ring-based records[32,33,34,35,36,37,38,39] These studies in the Tianshan and Altai Mountains and in other high-mountains of the world[40,41], showed that climate change might have a harmful effect on tree growth and recent evidence reported that the lower forests can display “browning” over extensive areas in the boreal region[42]. Several studies showed that slightly higher temperatures and greater accumulation of carbon dioxide in the atmosphere accelerate the growth rate of species in forest ecosystems[44,45]
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