College of Forestry, Northwest A&F University, Tai Cheng Road No. 3, Yangling, Shaanxi 712100, China.
Qinling National Forest Ecosystem Research Station, Northwest A&F University, Tai Cheng Road No. 3, Yangling, Shaanxi 712100, China.
Tree Physiol. 2024 Oct 3;44(10). doi: 10.1093/treephys/tpae115.
In addition to inducing xylem embolism, freeze-thaw events can cause frost fatigue phenomena. Freezing temperature, freezing times, number of freeze-thaw cycles and frost drought can affect the level of freeze-thaw-induced embolism, but it is unknown whether there is an effect on frost fatigue. We assessed whether these frost-related factors changed frost fatigue in the three diffuse-porous species by simulating freeze-thaw treatments under different conditions. We also proposed a new metric, embolism area, in place of embolism resistance, to more accurately quantify the shift of the vulnerability curve after experiencing freeze-thaw-induced embolism and refilling. Frost fatigue caused vulnerability curves of all species to change from S-shaped to double S-shaped or even R-shaped curves. When exposed to a freeze-thaw event, Acer truncatum showed strong resistance to frost fatigue; in contrast, Populus (I-101 × 84 K) and Liriodendron chinense were more vulnerable. Changing freezing temperature and times did not impact the response to frost fatigue in the three species, but a greater number of freeze-thaw cycles and more severe frost drought significantly exacerbated their fatigue degree. Considering that frost fatigue may be a widespread phenomenon among temperate diffuse-porous species, more work is needed in the future to reveal the mechanisms of frost fatigue.
除了诱导木质部栓塞外，冻融事件还会引起霜疲劳现象。冻结温度、冻结时间、冻融循环次数和霜旱都会影响冻融诱导栓塞的程度，但尚不清楚它们对霜疲劳是否有影响。我们通过模拟不同条件下的冻融处理，评估了这些与霜有关的因素是否改变了三种散孔材的霜疲劳。我们还提出了一个新的指标——栓塞面积，以取代栓塞阻力，更准确地量化经历冻融诱导栓塞和再填充后脆弱性曲线的移动。霜疲劳使所有物种的脆弱性曲线从 S 形变为双 S 形甚至 R 形曲线。在经历冻融事件时，青榨槭表现出对霜疲劳的强抵抗力；相比之下，欧美杨 101×84K 和杂种鹅掌楸更容易受到影响。改变冻结温度和时间并不会影响三种物种对霜疲劳的反应，但更多的冻融循环和更严重的霜旱会显著加剧它们的疲劳程度。考虑到霜疲劳可能是温带散孔材中普遍存在的现象，未来需要做更多的工作来揭示霜疲劳的机制。
