Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> Establishing whether uptake of rainwater-recharged soil water (RRS) can increase plant transpiration in response to rainfall pulses requires an investigation to evaluate plant adaptability, especially in water-limited regions where rainwater is the only replenishable soil water source. In this study, the water sources from RRS and three soil layers, the predawn leaf water potential (<span class="inline-formula">Ψ<sub>pd</sub></span>), the midday leaf water potential (<span class="inline-formula">Ψ<sub>m</sub></span>), the gradient of leaf water potential (<span class="inline-formula">Ψ<sub>pd</sub>−Ψ<sub>m</sub></span>), and the plant transpiration in response to rainfall pulses were analyzed for two dominant tree species, <i>Hippophae rhamnoides</i> subsp. <i>sinensis</i> and <i>Populus tomentosa</i>, in pure and mixed plantations during the growing period (June–September). Mixed afforestation significantly enhanced <span class="inline-formula">Ψ<sub>pd</sub>−Ψ<sub>m</sub></span>, RRS uptake proportion (RUP), and the relative response of daily normalized sap flow (SF<span class="inline-formula"><sub>R</sub></span>) and reduced the water source proportion from the deep soil layer (100–200 cm) for both species (<span class="inline-formula"><i>P</i>&lt;0.05</span>). In pure and mixed plantations, the large <span class="inline-formula">Ψ<sub>pd</sub>−Ψ<sub>m</sub></span> was consistent with high SF<span class="inline-formula"><sub>R</sub></span> for <i>H. rhamnoides</i> and the small <span class="inline-formula">Ψ<sub>pd</sub>−Ψ<sub>m</sub></span> was consistent with low SF<span class="inline-formula"><sub>R</sub></span> for <i>P. tomentosa</i> in response to rainfall pulses. Therefore, <i>H. rhamnoides</i> and <i>P. tomentosa</i> exhibited anisohydric and isohydric behavior, respectively, and the former plant species was more sensitive to rainfall pulses than <i>P. tomentosa</i>. Furthermore, in pure plantations, the SF<span class="inline-formula"><sub>R</sub></span> was significantly affected by RUP and <span class="inline-formula">Ψ<sub>pd</sub>−Ψ<sub>m</sub></span> for <i>H. rhamnoides</i> and significantly influenced by <span class="inline-formula">Ψ<sub>pd</sub>−Ψ<sub>m</sub></span> for <i>P. tomentosa</i> (<span class="inline-formula"><i>P</i>&lt;0.05</span>). However, the SF<span class="inline-formula"><sub>R</sub></span> was significantly influenced by RUP and <span class="inline-formula">Ψ<sub>pd</sub>−Ψ<sub>m</sub></span> for both species in the mixed plantation. These results indicate that mixed afforestation enhanced the influence of RRS uptake on plant transpiration for these different rainfall-pulse-sensitive plants. This study provides insights into suitable plantation species selection and management considering the link between RRS uptake and plant transpiration in water-limited regions.

Highlights

  • Rainwater uptake by plant and water consumption in response to rainfall pulses drive the survival of 40 plant species and ecosystem ecohydrological processes, especially in arid and semiarid regions where rainwater is the only replenishable soil water source (Berkelhammer et al, 2020; Gebauer and Ehleringer, 2000; West et al, 2012)

  • These results indicate that mixed afforestation enhanced the influence of rainwater uptake to water consumption after rainfall pulse, regardless of sensitivity to rainfall pulses

  • The SFR was significantly influenced by rainwater uptake proportion (RUP) and Ψpd−Ψm for H. rhamnoides, but the SFR was only significantly influenced by Ψpd−Ψm for P. davidiana

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Summary

Introduction

Rainwater uptake by plant and water consumption in response to rainfall pulses drive the survival of 40 plant species and ecosystem ecohydrological processes, especially in arid and semiarid regions where rainwater is the only replenishable soil water source (Berkelhammer et al, 2020; Gebauer and Ehleringer, 2000; West et al, 2012). The variability and intermittency of rainfall, which plays an important role in plant water uptake and consumption (Swaffer et al, 2014; Wang et al, 2020), have been predicted to increase in water limited regions (Klein et al, 2014; Mendham et al, 2011). Clarifying the influence of rainwater uptake to plant water consumption after rainfall pulses is essential to understand the process of plant species adaptation in water limited 50 regions (Meier et al, 2018; Tfwala et al, 2019). Rainwater uptake by plant is expected to increase water consumption after a rainfall pulse (Cheng et al, 2006; Liu et al, 2019; Xu et al, 2012).

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