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.