Understanding tree physiological responses to fire is needed to accurately model post‐fire carbon processes and inform management decisions. Given trees can die immediately or at extended time periods after fire, we combined two experiments to assess the short‐ (one‐day) and long‐term (21‐months) fire effects on Pinus ponderosa sapling water transport. Native percentage loss of conductivity (nPLC), vulnerability to cavitation and xylem anatomy were assessed in unburned and burned saplings at lethal and non‐lethal fire intensities. Fire did not cause any impact on nPLC and xylem cell wall structure in either experiment. However, surviving saplings evaluated 21‐months post‐fire were more vulnerable to cavitation. Our anatomical analysis in the long‐term experiment showed that new xylem growth adjacent to fire scars had irregular‐shaped tracheids and many parenchyma cells. Given conduit cell wall deformation was not observed in the long‐term experiment, we suggest that the irregularity of newly grown xylem cells nearby fire wounds may be responsible for decreasing resistance to embolism in burned plants. Our findings suggest that hydraulic failure is not the main short‐term physiological driver of mortality for Pinus ponderosa saplings. However, the decrease in embolism resistance in fire‐wounded saplings could contribute to sapling mortality in the years following fire.

中文翻译：

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火对黄松树苗幼树茎水力学的短期和长期影响

需要了解树木对火的生理反应，才能准确地模拟火后碳过程并为管理决策提供依据。鉴于树木可能在火灾后立即死亡或在较长时间死亡，我们结合两个实验评估了短期（一天）和长期（21个月）火灾对美国黄松树苗幼树水运输的影响。在致死和非致死火强度下，在未燃烧和燃烧的幼树中评估了电导率的自然百分比损失（n PLC），对空化和木质部解剖的脆弱性。火灾没有造成任何影响ñ在任何一个实验中，PLC和木质部细胞壁结构都是如此。但是，射击后21个月评估的存活树苗更容易发生气蚀。我们在长期实验中的解剖分析表明，毗邻火疤的新木质部生长具有不规则形状的气管和许多实质细胞。鉴于在长期实验中未观察到导管细胞壁变形，我们建议在火伤附近新生长的木质部细胞的不规则性可能是造成烧伤植物抗栓塞性降低的原因。我们的发现表明，水力衰竭不是美国黄松树苗死亡的主要短期生理驱动力。但是，火伤幼树的抗栓塞性降低可能会导致火灾后的树苗死亡。