在较高纬度地区树木越冬过程中频繁经历冻融交替，该过程可通过诱导木质部产生气穴化栓塞而严重威胁树木的水分传输安全，从而造成树木越冬伤害、死亡，甚至引发森林衰退等林业问题。在该环境中，越冬过程中木质部栓塞的抵抗力和修复作用对树木的存活和生长至关重要，但相关过程和机理仍不明确，亟需开展相关的树木生理研究。本项目拟依托长白山森林生态系统研究站，通过同质园测定、跨海拔梯度测定和幼苗实验，开展树木木质部冬季栓塞相关的抗逆生理研究。将明确该区主要造林树种的木质部水力结构差异，揭示水分传输效率和安全性对树木生产力和抗逆性的影响机制；探讨冬季栓塞风险随环境梯度发生变化时，光合产物在结构性生长和非结构性碳水化合物储存间分配的变化规律；揭示幼苗碳水化合物储存和再活化对冬季栓塞修复的影响机制。以期为该区造林树种选育、森林生产力提高、林下更新障碍解除等林业实践提供科学依据。

In forest ecosystems of relatively high latitudes, freeze-thaw cycles frequently occur in the cold seasons and often induce xylem embolism in overwintering organs of trees, i.e. the blockage of water conducting conduits by air bubbles. Xylem embolism caused by freeze-thaw cycles can result in reduced hydraulic conductivity and even hydraulic failure and thus often cause tree damage, mortality or even large-scale forest decline in temperate regions. Keeping hydraulic integrity through enhancing winter embolism resistance or by an effective winter embolism repair process is critical to temperate forest tree species but the underlying mechanisms are still waiting for further investigations. For this proposed project, xylem hydraulics related to winter embolism resistance and repair will be investigated at the Forest Ecosystem Research Station of Changbai Mountain using a combination of three approaches, i.e. a common garden comparative study among dominant tree species, a intra-specific comparative study across the altitudinal gradient, and a seedling experiment under controlled light conditions. We have three major objectives for this project: 1) to clarify the structural and functional differences in traits related to hydraulic architecture and find out whether differences in the way of coping with winter embolism result in interspecific differences in productivity and stress tolerance; 2) to investigate the pattern of coordinated changes between structural growth and storage of non-structural carbohydrates along the environmental gradient where different risks of winter embolism are expected to occur; and 3) to investigate the mechanistic association between winter embolism refilling and non-structural carbohydrate storage and remobilization. Besides its own merits in tree physiological studies, this project will provide a sound scientific basis for improving practices in forestry, such as the selection of more suitable tree species for afforestation according to local environmental conditions, enhancement forest productivity, and dealing with the problem of natural regeneration failure for some founder species in natural forests of Northeast China.