Non-Structural Carbohydrate Storage Strategy Explains the Spatial Distribution of Treeline Species.

Hudong Han,Shengwei Zong,Hongshi He,Yan Li,Yu Cong,Yuanyuan Fu,Changbao Yu,Zhengfang Wu,Hang Sun,Jindan Xu,Jianan He,Kai Liu

doi:10.3390/plants9030384

Abstract

Environmental factors that drive carbon storage are often used as an explanation for alpine treeline formation. However, different tree species respond differently to environmental changes, which challenges our understanding of treeline formation and shifts. Therefore, we selected Picea jezoensis and Betula ermanii, the two treeline species naturally occurring in Changbai Mountain in China, and measured the concentration of non-structural carbohydrates (NSC), soluble sugars and starch in one-year-old leaves, shoots, stems and fine roots at different elevations. We found that compared with P. jezoensis, the NSC and soluble sugars concentrations of leaves and shoots of B. ermanii were higher than those of P. jezoensis, while the starch concentration of all the tissues were lower. Moreover, the concentration of NSC, soluble sugars and starch in the leaves of B. ermanii decreased with elevation. In addition, the starch concentration of B. ermanii shoots, stems and fine roots remained at a high level regardless of whether the soluble sugars concentration decreased. Whereas the concentrations of soluble sugars and starch in one-year-old leaves, shoots and stems of P. jezoensis responded similarly changes with elevation. These findings demonstrate that compared with P. jezoensis, B. ermanii has a higher soluble sugars/starch ratio, and its shoots, stems and fine roots actively store NSC to adapt to the harsh environment, which is one of the reasons that B. ermanii can be distributed at higher altitudes.

Highlights

The alpine treeline is the upper limit of mountain forest distribution and is highly sensitive to climate change and human disturbance [1,2]
non-structural carbohydrates (NSC) concentrations is an important indicator that reflects the response of the trees to environmental changes [13,19]
Li et al (2015) concluded that the concentrations of NSC, soluble sugars and starch of leaves in different forest trees were negatively correlated with temperature [28]

Summary

Introduction

The alpine treeline is the upper limit of mountain forest distribution and is highly sensitive to climate change and human disturbance [1,2]. Upward shifts of the alpine treeline have been observed in most areas [3,4,5,6,7], while some more drought-prone areas have remained unchanged, or even moved downward [8,9,10,11]. Different tree species vary in their responses to environmental changes [13]. As a result of the asynchrony of alpine treeline shift and climate change, Plants 2020, 9, 384; doi:10.3390/plants9030384 www.mdpi.com/journal/plants. Plants 2020, 9, 384 an enormous challenge has been brought to predict future alpine treeline shifts. Studying two different treeline species in response to environmental changes will help to explain the formation and shifts of the alpine treeline

Objectives

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Results

Conclusion