Bravo-Avila Catherine H, Feeley Kenneth J
Department of Biology, University of Miami, Coral Gables, FL 33146, USA.
Fairchild Tropical Botanical Garden, Coral Gables, FL 33156, USA.
Plants (Basel). 2023 Aug 16;12(16):2957. doi: 10.3390/plants12162957.
Little is known about how differences in water availability within the "super humid" tropics can influence the physiology of understory plant species and the composition of understory plant communities. We investigated the variation in the physiological drought tolerances of hundreds of understory plants in dozens of plant communities across an extreme elevation and precipitation gradient. Specifically, we established 58 understory plots along a gradient of 400-3600 m asl elevation and 1000-6000 mm yr rainfall in and around Manu National Park in southeastern Peru. Within the plots, we sampled all understory woody plants and measured three metrics of physiological leaf drought tolerance-turgor loss point (TLP), cuticular conductance (G), and solute leakage (SL)-and assessed how the community-level means of these three traits related to the mean annual precipitation (MAP) and elevation (along the study gradient, the temperature decreases linearly, and the vapor pressure deficit increases monotonically with elevation). We did not find any correlations between the three metrics of leaf drought tolerance, suggesting that they represent independent strategies for coping with a low water availability. Despite being widely used metrics of leaf drought tolerance, neither the TLP nor G showed any significant relationships with elevation or the MAP. In contrast, SL, which has only recently been developed for use in ecological field studies, increased significantly at higher precipitations and at lower elevations (i.e., plants in colder and drier habitats have a lower average SL, indicating greater drought tolerances). Our results illustrate that differences in water availability may affect the physiology of tropical montane plants and thus play a strong role in structuring plant communities even in the super humid tropics. Our results also highlight the potential for SL assays to be efficient and effective tools for measuring drought tolerances in the field.
关于“超级湿润”热带地区内水分可利用性的差异如何影响林下植物物种的生理特征以及林下植物群落的组成，我们所知甚少。我们调查了数十个植物群落中数百种林下植物在极端海拔和降水梯度下生理干旱耐受性的变化。具体而言，我们在秘鲁东南部马努国家公园及其周边，沿着海拔400 - 3600米和年降雨量1000 - 6000毫米的梯度建立了58个林下样地。在这些样地内，我们对所有林下木本植物进行了采样，并测量了生理叶片干旱耐受性的三个指标——膨压丧失点（TLP）、角质层导度（G）和溶质渗漏（SL），并评估了这三个性状的群落水平均值与年平均降水量（MAP）和海拔的关系（沿着研究梯度，温度呈线性下降，蒸气压亏缺随海拔单调增加）。我们没有发现叶片干旱耐受性的三个指标之间存在任何相关性，这表明它们代表了应对低水分可利用性的独立策略。尽管TLP和G是广泛使用的叶片干旱耐受性指标，但它们与海拔或MAP均未显示出任何显著关系。相比之下，SL是最近才开发用于生态野外研究的指标，在较高降水量和较低海拔处显著增加（即生活在较冷和较干燥栖息地的植物平均SL较低，表明其耐旱性更强）。我们的结果表明，水分可利用性的差异可能会影响热带山地植物的生理特征，从而在构建植物群落中发挥重要作用，即使在超级湿润的热带地区也是如此。我们的结果还突出了SL测定作为在野外测量耐旱性的高效有效工具的潜力。
