Wright Cynthia L, de Lima André L A, de Souza Eduardo S, West Jason B, Wilcox Bradford P
Environmental Sciences Division Oak Ridge National Laboratory Oak Ridge TN USA.
Ecology and Conservation Biology Texas A&M University College Station TX USA.
Ecol Evol. 2021 Aug 4;11(17):11808-11825. doi: 10.1002/ece3.7949. eCollection 2021 Sep.
In seasonally dry tropical forests, plant functional type can be classified as deciduous low wood density, deciduous high wood density, or evergreen high wood density species. While deciduousness is often associated with drought-avoidance and low wood density is often associated with tissue water storage, the degree to which these functional types may correspond to diverging and unique water use strategies has not been extensively tested.We examined (a) tolerance to water stress, measured by predawn and mid-day leaf water potential; (b) water use efficiency, measured via foliar δC; and (c) access to soil water, measured via stem water δO.We found that deciduous low wood density species maintain high leaf water potential and low water use efficiency. Deciduous high wood density species have lower leaf water potential and variable water use efficiency. Both groups rely on shallow soil water. Evergreen high wood density species have low leaf water potential, higher water use efficiency, and access alternative water sources. These findings indicate that deciduous low wood density species are drought avoiders, with a specialized strategy for storing root and stem water. Deciduous high wood density species are moderately drought tolerant, and evergreen high wood density species are the most drought tolerant group.. Our results broadly support the plant functional type framework as a way to understand water use strategies, but also highlight species-level differences.
在季节性干燥的热带森林中，植物功能类型可分为落叶低木材密度、落叶高木材密度或常绿高木材密度物种。虽然落叶通常与干旱规避相关，低木材密度通常与组织水分储存相关，但这些功能类型在何种程度上可能对应于不同且独特的水分利用策略尚未得到广泛测试。我们研究了：（a）通过黎明前和中午叶片水势测量的水分胁迫耐受性；（b）通过叶片δC测量的水分利用效率；以及（c）通过茎干水δO测量的土壤水分获取情况。我们发现，落叶低木材密度物种保持高叶片水势和低水分利用效率。落叶高木材密度物种具有较低的叶片水势和可变的水分利用效率。这两组都依赖浅层土壤水。常绿高木材密度物种具有低叶片水势、较高的水分利用效率，并能获取其他水源。这些发现表明，落叶低木材密度物种是干旱规避者，具有储存根和茎水分的特殊策略。落叶高木材密度物种具有中等耐旱性，而常绿高木材密度物种是最耐旱的群体。我们的结果广泛支持将植物功能类型框架作为理解水分利用策略的一种方式，但也突出了物种水平的差异。
