碳供给与碳利用对树木生长的限制机制

doi:10.17521/cjpe.2019.0104

摘要/Abstract

摘要：

树木生长固碳过程使森林生态系统成为减缓大气CO₂浓度升高的一个巨大而持续的碳汇。根据树木可利用碳的状况, 限制树木生长的机制可分为碳供给限制和碳利用限制。许多环境因子交互作用, 共同影响树木的碳供给与碳利用, 因而很难量化碳供给和碳利用活动及其对环境变化敏感性对树木生长的影响。因此, 从碳供给与碳利用角度揭示环境变化对树木生长影响的生理机制, 对于预测全球变化背景下树木生长及森林碳汇功能至关重要。为此, 该文介绍了树木生长碳供给与碳利用限制争议的相关背景; 从碳供给与碳利用角度探讨了叶损失、干旱和低温等胁迫条件限制树木生长的生理机制; 提出该领域今后应优先研究的3个问题: (1)探索非结构性碳水化合物(NSC)储存形成的调控机制, 确定什么情况下以及多大程度上树木通过主动降低生长而将光合产物优先分配给NSC储存; (2)加强碳利用活动研究, 系统测定光合产物在其碳利用组分的分配(特别是根系及其共生微生物活动); (3)开展树木碳代谢、矿质营养与水分生理的互作研究, 充分认识树木碳、水和养分耦合关系及对树木生长的影响。

关键词: 碳利用, 碳供给, 非结构性碳水化合物, 胁迫, 树木生长

Abstract:

Forests are large and persistent carbon (C) sink mainly through the C sequestration of tree growth, which can mitigate the rising rate of CO₂ concentration in the atmosphere. According to C availability in trees, two mechanisms involved in controlling tree growth are attributed to limitations to C input and C utilities. Since many environmental factors influence the activities of C-source and C-sink of trees interdependently, it is difficult to quantify how the sensitivity of C-source or C-sink activity to environmental changes affects tree growth. Therefore, it is of significance to understand physiological mechanisms underlying potential limitations to tree growth in order to predict tree growth and forest C sink under global change scenarios. In this review, the debates on the C-source and C-sink limitations to tree growth were firstly introduced. Second, we discussed responses of tree growth to biotic and abiotic stresses, such as defoliation, drought and low temperature from the perspective of C-source/sink limitations. Finally, we proposed three priorities for future studies in this field: (1) to explore the regulating mechanisms on the allocation of non-structural carbohydrates (NSC) in trees, and to determine what conditions and what extent trees actively allocate the photosynthates to NSC storage at the expense of growth; (2) to strengthen studies on the tree C-sink, and determine the photosynthates allocated to all components of tree C-sink, especially the missing C-sinks such as the activities of roots and related microorganisms; and (3) to implement studies on interactions among C metabolism, mineral nutrition and hydraulics physiology, and fully understand the C-water-nutrient coupling and its effects on tree growth.

Key words: carbon sink, carbon source, non-structural carbohydrates, stress, tree growth

王兆国, 王传宽. 碳供给与碳利用对树木生长的限制机制. 植物生态学报, 2019, 43(12): 1036-1047. DOI: 10.17521/cjpe.2019.0104

WANG Zhao-Guo, WANG Chuan-Kuan. Mechanisms of carbon source-sink limitations to tree growth. Chinese Journal of Plant Ecology, 2019, 43(12): 1036-1047. DOI: 10.17521/cjpe.2019.0104

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2019.0104

https://www.plant-ecology.com/CN/Y2019/V43/I12/1036

图/表 1

图1 树木生长的碳供给与碳利用限制机制概念框架。a-b-c路径, 生物和非生物胁迫(如叶损失、干旱或低温等)减少光合作用碳固定, 非结构性碳水化合物(NSC)浓度降低, 从而降低树木生长(碳供给限制); d-e-c路径, 面对胁迫, 树木主动储备NSC, 减少可利用碳, 从而降低树木生长(碳供给限制); f-h-i路径, 生物和非生物胁迫直接限制树木生长(碳利用限制), 过剩的NSC通过反馈作用抑制光合作用。实线指直接作用, 虚线指反馈作用;+指正效应, –指负效应。

Fig. 1 A conceptual framework of the mechanisms of carbon source-sink limitations to tree growth. From a-b-c pathway, carbon assimilation is reduced by biotic and abiotic stresses (such as defoliation, drought and low temperature), hence tree growth is limited by available carbon (i.e. carbon source limitation). From d-e-c pathway, the storage of non-structural carbohydrates (NSC) is an active process, which decreases available carbon for tree growth (carbon source limitation). From f-h-i pathway, tree growth is constrained by biotic and abiotic stresses directly, leading to NSC accumulation and thus limitation to photosynthesis (i.e. carbon sink limitation). Solid lines represent direct effects, and dotted lines represent feedbacks. + and - represent positive and negative effects, respectively.

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