Data from: Initial hydraulic failure followed by late-stage carbon starvation leads to drought-induced death in tree, Trema orientalis

Drought-induced tree death has become a serious problem in global forest
ecosystems. Two nonexclusive hypotheses, hydraulic failure and carbon
starvation, have been proposed to explain tree die-offs. To clarify the
mechanisms, we investigated the physiological processes of drought-induced
tree death in saplings with contrasting Huber values (sapwood area/total
leaf area). First, hydraulic failure and reduced respiration were found in
the initial process of tree decline, and in the last stage carbon
starvation leaded to tree death. The carbohydrate reserves at the stem
bases, low in healthy trees, were accumulated at the beginning of the
declining process because of phloem transport failure, and then decreased
just before dying. The concentrations of non-structural carbohydrates at
the stem bases are a good indicator of tree damage. The physiological
processes and carbon sink-source dynamics that occur during lethal drought
provide important insight into the adaptive measures underlying forest
die-offs under global warming conditions.

干旱诱导的树木死亡已成为全球森林生态系统面临的严峻问题。目前已有两种非互斥假说用以解释树木死亡现象，分别为水力衰竭与碳饥饿。为阐明该机制，本研究针对具有差异化胡贝尔值（Huber value，即边材面积/总叶面积）的幼树，探究了干旱诱导树木死亡的生理过程。研究发现，在树木衰退的初始阶段，会发生水力衰竭与呼吸作用减弱；而在衰退末期，碳饥饿则会导致树木死亡。健康树木茎基部的碳水化合物储备本就较低，而在衰退初期，由于韧皮部运输受阻，茎基部碳水化合物储备会出现累积，随后在植株死亡前夕再度下降。茎基部的非结构性碳水化合物浓度可作为树木受损伤程度的良好指示指标。致死干旱过程中发生的生理过程与碳汇源动态变化，为理解全球变暖背景下森林死亡背后的适应性策略提供了重要见解。