Chair of Ecophysiology and Vegetation Ecology, Julius-von-Sachs Institute of Biological Sciences, University of Würzburg, Würzburg, Germany.
Chair of Forest Botany, Institute of Forest Botany and Forest Zoology, Technische Universität Dresden, Tharandt, Germany.
Plant Biol (Stuttg). 2023 Dec;25(7):1171-1185. doi: 10.1111/plb.13573. Epub 2023 Sep 13.
The increasing frequency of global change-type droughts has created a need for fast, accurate and widely applicable techniques for estimating xylem embolism resistance to improve forecasts of future forest changes. We used data from 12 diffuse-porous temperate tree species covering a wide range of xylem safety to compare the pneumatic and flow-centrifuge method, two rapid methods used for constructing xylem vulnerability curves. We evaluated the agreement between parameters estimated with both methods and the sensitivity of pneumatic measurements to the duration of air discharge (AD) measurements. There was close agreement between xylem water potentials at 50% air discharged (PAD), estimated with the Pneumatron, and 50% loss of hydraulic conductivity (PLC), estimated with the flow-centrifuge method (mean signed deviation: 0.12 MPa, Pearson correlation: 0.96 after 15 s of gas extraction). However, the relationship between the estimated slopes was more variable, resulting in lower agreement in the xylem water potential at 12% and 88% PAD/PLC. The agreement between the two methods was not affected by species-specific vessel length distributions. All pneumatic parameters were sensitive to AD time. Overall agreement was highest at relatively short AD times, with an optimum at 16 s. Our results highlight the value of the Pneumatron as an easy and reliable tool to estimate 50% embolism thresholds for a wide range of diffuse-porous temperate angiosperms. Further, our study provides a set of useful metrics for methodological comparisons of vulnerability curves in terms of systematic and random deviations, as well as overall agreement.
全球变化型干旱的频率不断增加，这就需要快速、准确和广泛适用的技术来评估木质部栓塞阻力，以提高对未来森林变化的预测。我们使用了来自 12 种具有广泛木质部安全范围的散孔温带树种的数据，比较了用于构建木质部脆弱性曲线的两种快速方法，即气动法和流动离心法。我们评估了这两种方法估计的参数之间的一致性，以及气动测量对空气排出（AD）测量持续时间的敏感性。用 Pneumatron 估计的木质部水势在 50%空气排出时（PAD）与用流动离心法估计的 50%水力传导率损失（PLC）非常吻合（平均符号偏差：0.12 MPa，Pearson 相关系数：气体提取 15 秒后为 0.96）。然而，估计斜率之间的关系更加多变，导致在 12%和 88% PAD/PLC 时木质部水势的一致性较低。这两种方法之间的一致性不受种特异性导管长度分布的影响。所有气动参数都对 AD 时间敏感。在相对较短的 AD 时间内，整体一致性最高，最佳时间为 16 秒。我们的研究结果突出了 Pneumatron 作为一种简单可靠的工具的价值，可用于广泛的散孔温带被子植物的 50%栓塞阈值的估计。此外，我们的研究提供了一套有用的指标，用于从系统和随机偏差以及整体一致性方面比较脆弱性曲线的方法。
