DataSheet_1_Hydraulic trade-off and coordination strategies mediated by leaf functional traits of desert shrubs.docx

Desert shrubs play important roles in desertification control and vegetation restoration, which are particularly affected by droughts caused by climate change. However, the hydraulic strategies associated with hydraulic functional traits of desert shrubs remain unclear. Here, eight desert shrub species with different life forms and morphologies were selected for a common garden experiment at the southeast edge of the Tengger Desert in northern China to study the hydraulic strategies mediated by leaf hydraulic functional traits. Diurnal leaf water potential change, leaf hydraulic efficiency and safety, hydraulic safety margin, hydraulic capacitance, and water potential and relative water content at the turgor loss point were observed to significantly differ among species, suggesting that leaf hydraulic functional traits were strongly associated with species even when living in the same environment. Additionally, shrubs with greater leaf hydraulic efficiency had lower midday leaf water potential and leaf hydraulic safety, suggesting that leaf hydraulic efficiency had a strong trade-off with hydraulic safety and minimum leaf water potential, whereas there was also a coordination between leaf hydraulic safety and the leaf minimal water potential. Moreover, shrubs with higher leaf hydraulic capacitance had greater hydraulic safety margins, indicating coordination between leaf hydraulic capacitance and hydraulic safety margin. Overall, this study indicated that minimal daily leaf water potential, as an easily measured parameter, may be used preliminarily to predict leaf hydraulic conductivity and the resistance to embolism of desert shrubs, providing critical insights into hydraulic trade-off and coordination strategies for native shrubs as priority species in desert vegetation restoration and reconstruction.

荒漠灌木在荒漠化防治与植被恢复中发挥着关键作用，但其生存极易受到气候变化引发的干旱胁迫影响。然而，与荒漠灌木水力功能性状（hydraulic functional traits）相关的水力策略仍未得到明确阐释。本研究选取8种具有不同生活型与形态特征的荒漠灌木，在中国北方腾格里沙漠东南缘开展同质园实验（common garden experiment），以探究叶片水力功能性状介导的水力策略。研究观测显示，不同物种的日间叶水势变化、叶片水力效率与安全性、水力安全裕度（hydraulic safety margin）、水力容度（hydraulic capacitance）以及膨压丧失点（turgor loss point）处的水势与相对含水量均存在显著差异，这表明即便处于相同环境中，叶片水力功能性状仍与物种特性紧密关联。此外，叶片水力效率更高的灌木，其正午叶水势与叶片水力安全性更低，说明叶片水力效率与水力安全性、最低叶水势之间存在显著权衡（trade-off）关系，而叶片水力安全性与最低叶水势则呈现协同特征。进一步而言，叶片水力容度更高的灌木，其水力安全裕度也更大，表明叶片水力容度与水力安全裕度之间存在协同关系。综上，本研究表明，作为一项易于测定的参数，日间最低叶水势可初步用于预测荒漠灌木的叶片水力导度（leaf hydraulic conductivity）与抗栓塞能力（resistance to embolism），为将本土灌木作为荒漠植被恢复与重建的优先物种提供了关于水力权衡与协同策略的关键理论依据。