Abstract
Precise and accurate estimation of key hydraulic points of plants is conducive to mastering the hydraulic status of plants under drought stress. This is crucial to grasping the hydraulic status before the dieback period to predict and prevent forest mortality. We tested three key points and compared the experimental results to the calculated results by applying two methods. Saplings (n = 180) of Robinia pseudoacacia L. were separated into nine treatments according to the duration of the drought and rewatering. We established the hydraulic vulnerability curve and measured the stem water potential and loss of conductivity to determine the key points. We then compared the differences between the calculated [differential method (DM) and traditional method (TM)] and experimental results to identify the validity of the calculation method. From the drought-rewatering experiment, the calculated results from the DM can be an accurate estimation of the experimental results, whereas the TM overestimated them. Our results defined the hydraulic status of each period of plants. By combining the experimental and calculated results, we divided the hydraulic vulnerability curve into four parts. This will generate more comprehensive and accurate methods for future research.
Highlights
Patterns of precipitation have substantially changed owing to global climate change, and in several parts of the world, the total precipitation has gradually decreased (Easterling et al, 2000; Högy et al, 2013; Gimbel et al, 2015; Ge et al, 2017; Oliveira et al, 2019)
Hydraulic failure caused by embolism has been invoked as the Differential Method in Hydraulics Calculating most direct and critical mechanism that causes forest mortality (Martinez-Vilalta and Pinol, 2002; Nardini et al, 2013; O’Grady et al, 2013; Liu et al, 2018), which initially resulted in tree dieback and led to extensive tree death
This is different from the gymnosperms calculating point Ψ 50 (Choat et al, 2012) and the global synthesis reported by Adams et al (2017), in which the trees died when the hydraulic failure exhibited more than a 0.60 loss of conductivity (LC) in all cases
Summary
Patterns of precipitation have substantially changed owing to global climate change, and in several parts of the world, the total precipitation has gradually decreased (Easterling et al, 2000; Högy et al, 2013; Gimbel et al, 2015; Ge et al, 2017; Oliveira et al, 2019). By combining the vulnerability curves and half-lethal effect, Hammond et al (2019) studied the Ψ l of Pinus taeda L., and they reported that Ψ l of P. taeda has a pressure that can cause a 0.80 LC. This is different from the gymnosperms calculating point Ψ 50 (Choat et al, 2012) and the global synthesis reported by Adams et al (2017), in which the trees died when the hydraulic failure exhibited more than a 0.60 LC in all cases. They strongly recommended that continued experimentation is necessary to assess the different tree species, populations, and individuals in different ontogeny stages
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