Max Planck Institute for Biogeochemistry, Hans Knoll Str. 10, 07745, Jena, Germany.
New Phytol. 2013 Oct;200(2):340-349. doi: 10.1111/nph.12331. Epub 2013 May 21.
Drought-induced tree mortality results from an interaction of several mechanisms. Plant water and carbon relations are interdependent and assessments of their individual contributions are difficult. Because drought always affects both plant hydration and carbon assimilation, it is challenging to disentangle their concomitant effects on carbon balance and carbon translocation. Here, we report results of a manipulation experiment specifically designed to separate drought effects on carbon and water relations from those on carbon translocation. In a glasshouse experiment, we manipulated the carbon balance of Norway spruce saplings exposed to either drought or carbon starvation (CO2 withdrawal), or both treatments, and compared the dynamics of carbon exchange, allocation and storage in different tissues. Drought killed trees much faster than did carbon starvation. Storage C pools were not depleted at death for droughted trees as they were for starved, well-watered trees. Hence drought has a significant detrimental effect on a plant's ability to utilize stored carbon. Unless they can be transported to where they are needed, sufficient carbon reserves alone will not assure survival of a drought except under specific conditions, such as moderate drought, or in species that maintain plant water relations required for carbon re-mobilization.
干旱导致的树木死亡是多种机制相互作用的结果。植物的水分和碳关系是相互依存的，评估它们各自的贡献是困难的。由于干旱总是同时影响植物的水合作用和碳同化作用，因此很难将它们对碳平衡和碳转运的伴随影响分开。在这里，我们报告了一项专门设计的操纵实验的结果，该实验旨在将干旱对碳和水分关系的影响与对碳转运的影响分开。在温室实验中，我们操纵了暴露于干旱或碳饥饿（CO2 撤离）或两种处理的挪威云杉幼苗的碳平衡，并比较了不同组织中碳交换、分配和储存的动态。干旱导致树木死亡的速度比碳饥饿快得多。对于干旱的树木来说，在死亡时，储存的 C 池并没有像饥饿的、水分充足的树木那样耗尽。因此，干旱对植物利用储存碳的能力有显著的不利影响。除非它们能够被运输到需要的地方，否则仅仅足够的碳储备不足以保证干旱下的生存，除非在特定条件下，如适度干旱，或在那些维持植物水分关系以进行碳再动员的物种中。
