Background and aims

Understanding the variation of root hydraulic conductance (L_p) is critical for the simulation of the soil–plant-atmosphere continuum (SPAC), but its monitoring remains challenging. In this study, we introduce a new non-destructive method for characterizing L_p dynamics in woody species through the combination of simultaneous determinations of sap flow and xylem water potential. Recent studies indicate that modern microtensiometers provide robust estimates of xylem water potential, but it is unknown whether they allow tracking rapid changes in water potential without significant time lags, which may have implications for the proposed methodology.

Methods

The impulse response of microtensiometers was measured in the lab, developing a procedure for correcting sensor data by deconvolution. Then, microtensiometers and compensation heat pulse sensors were used to evaluate the variations in L_p in two well-watered olive trees during the summer of 2022 in Cordoba, Spain.

Results

Correcting microtensiometer outputs was critical to analyze our field data as strong stomatal oscillations occurred, with microtensiometers damping xylem water potential variations. By contrast, our results suggest that correction procedures may not be required for many practical applications like irrigation scheduling. The daytime values of L_p were close to those obtained in previous studies, while nighttime values were extremely low. Therefore, a proportionality between L_p and sap flow rate was observed, which agrees with previous studies, although it does not prove a causal relationship.

Conclusions

The methods proposed here could be applied to studying the temporal dynamics of root hydraulic conductance in other tree species.

中文翻译：

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使用微张力计和液流传感器测量橄榄树根部电导的日变化

 背景和目标

了解根系水导率 ( L _p ) 的变化对于土壤-植物-大气连续体 (SPAC) 的模拟至关重要，但其监测仍然具有挑战性。在这项研究中，我们引入了一种新的非破坏性方法，通过同时测定树液流量和木质部水势来表征木本物种的L _p动态。最近的研究表明，现代微张力计可以对木质部水势进行可靠的估计，但尚不清楚它们是否允许在没有显着时间滞后的情况下跟踪水势的快速变化，这可能对所提出的方法产生影响。

 方法

在实验室中测量了微张力计的脉冲响应，开发了一种通过反卷积校正传感器数据的程序。然后，使用微张力计和补偿热脉冲传感器评估 2022 年夏季西班牙科尔多瓦两棵浇水良好的橄榄树的L _p变化。

 结果

校正微张力计输出对于分析我们的现场数据至关重要，因为发生了强烈的气孔振荡，微张力计抑制了木质部水势的变化。相比之下，我们的结果表明，许多实际应用（例如灌溉计划）可能不需要校正程序。 L _p的白天值与之前研究中获得的值接近，而夜间值极低。因此，观察到L _p和液流速率之间存在比例关系，这与之前的研究一致，尽管它没有证明因果关系。

 结论

这里提出的方法可以应用于研究其他树种根系导水率的时间动态。