The heat plume associated with fire has been hypothesized to cause sufficient water loss from trees to induce embolism and hydraulic failure. However, it is unclear whether the water transport path remains sufficiently intact during scorching or burning of foliage to sustain high water loss. We measured water uptake by branches of Magnolia grandiflora while exposing them to a range of fire intensities and examined factors influencing continued water uptake after fire. Burning caused a 22-fold mean increase in water uptake, with greatest rates of water loss observed at burn intensities that caused complete consumption of leaves. Such rapid uptake is possible only with steep gradients in water potential, which would likely result in substantial cavitation of xylem and loss of conductivity in intact stems. Water uptake continued after burning was complete and was greatest following burn intensities that killed leaves but did not consume them. This post-fire uptake was mostly driven by rehydration of the remaining tissues, rather than evaporation from the tissues. Our results indicate that the fire plume hypothesis can be expanded to include a wide range of burning conditions experienced by plants. High rates of water loss are sustained during burning, even when leaves are killed or completely consumed.

中文翻译：

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水力分段不能保护茎在火灾期间避免急性失水

与火灾相关的热羽被假设会导致树木中的水分流失，从而引发栓塞和液压故障。然而，尚不清楚在叶子的灼烧或燃烧过程中，水分输送路径是否保持足够完整以维持高水分流失。我们测量了广玉兰枝条的吸水量同时将它们暴露在一定范围的火灾强度下，并检查影响火灾后持续吸水的因素。燃烧导致吸水量平均增加 22 倍，在导致完全消耗叶子的燃烧强度下观察到最大的水分流失率。这种快速吸收只有在水势陡峭的梯度下才有可能，这可能会导致木质部的大量空化和完整茎的导电性损失。燃烧完成后继续吸水，并且在杀死叶子但没有消耗叶子的燃烧强度之后吸水量最大。这种火灾后吸收主要是由剩余组织的再水化驱动的，而不是从组织中蒸发。我们的结果表明，火羽假说可以扩展到包括植物经历的各种燃烧条件。