Current and potential tree locations in tree line ecotone of Changbai Mountains, Northeast China: the controlling effects of topography.

Shengwei Zong,Xiaofeng Gao,Lei Wang,Zhengfang Wu,Haibo Du,Hongshi He,Ming Li,Jiawei Xu,Eryuan Liang

doi:10.1371/journal.pone.0106114

Shengwei Zong, Xiaofeng Gao + Show 7 more

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https://doi.org/10.1371/journal.pone.0106114

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Abstract

Tree line ecotone in the Changbai Mountains has undergone large changes in the past decades. Tree locations show variations on the four sides of the mountains, especially on the northern and western sides, which has not been fully explained. Previous studies attributed such variations to the variations in temperature. However, in this study, we hypothesized that topographic controls were responsible for causing the variations in the tree locations in tree line ecotone of the Changbai Mountains. To test the hypothesis, we used IKONOS images and WorldView-1 image to identify the tree locations and developed a logistic regression model using topographical variables to identify the dominant controls of the tree locations. The results showed that aspect, wetness, and slope were dominant controls for tree locations on western side of the mountains, whereas altitude, SPI, and aspect were the dominant factors on northern side. The upmost altitude a tree can currently reach was 2140 m asl on the northern side and 2060 m asl on western side. The model predicted results showed that habitats above the current tree line on the both sides were available for trees. Tree recruitments under the current tree line may take advantage of the available habitats at higher elevations based on the current tree location. Our research confirmed the controlling effects of topography on the tree locations in the tree line ecotone of Changbai Mountains and suggested that it was essential to assess the tree response to topography in the research of tree line ecotone.

Highlights

Tree line is considered as an important indicator of terrestrial ecosystems to climate change because it is sensitive to environmental change
The current tree locations on the western side are subject to the windthrow effect
The western side is on the windward side and westerly winds prevail during the growing season [34]

Summary

Introduction

Tree line is considered as an important indicator of terrestrial ecosystems to climate change because it is sensitive to environmental change. The responses of tree species around tree line to the climate warming differ in different regions. Some researches show that tree line species are responsive to changes in summer temperature [6], whereas others suggest that winter temperature may have important effects [7,8]. The warming in the past 200 year is already having a significant impact on the population density of the trees, but not on the position of the Smith fir tree line [10]. In mountainous regions, topography may control local environments including microclimates, soil properties, and disturbances [12] and exerts a strong influence on vegetation distribution and succession in tree line ecotone [13,14]. It is essential to assess the response of tree species to topography in tree line ecotone

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Conclusion