Zhang Yuhan, Zhao Jiale, Xu Jinshi, Chai Yongfu, Liu Peiliang, Quan Jiaxin, Wu Xipin, Li Cunxia, Yue Ming
Key Laboratory of Resource Biology and Biotechnology in Western China, Northwest University, Xi'an, China.
Xi'an Botanical Garden of Shaanxi Province/Institute of Botany of Shaanxi Province, Xi'an, China.
Front Plant Sci. 2022 May 26;13:902509. doi: 10.3389/fpls.2022.902509. eCollection 2022.
Water availability is a key environmental factor affecting plant species distribution, and the relationships between hydraulic and economic traits are important for understanding the species' distribution patterns. However, in the same community type but within different soil water availabilities, the relationships in congeneric species remain ambiguous. In northwest China, forests in the Qinling Mountains (QM, humid region) and Loess Plateau (LP, drought region) have different species composition owing to contrasting soil water availability, but with common species occurring in two regions. We analyzed eight hydraulic traits [stomatal density (SD), vein density (VD), wood specific gravity (WSG), lower leaf area: sapwood area (Al: As), stomatal length (SL), turgor loss point (Ψ), maximum vessel diameter (Vd) and height (Height)] and five economic traits [leaf dry matter content (LDMC), leaf tissue density (TD), leaf dry mass per area (LMA), Leaf thickness (LT) and maximum net photosynthetic rate (P)] of congeneric species (including common species and endemic species) in forests of QM and LP. We explored whether the congeneric species have different economic and hydraulic traits across regions. And whether the relationship between hydraulic and economic traits was determined by soil water availability, and whether it was related to species distribution and congeneric endemic species composition of the same community. We found that LP species tended to have higher SD, VD, WSG, Al: As, SL, Ψ and Vd than QM species. There was a significant trade-off between hydraulic efficiency and safety across congeneric species. Also, the relationships between hydraulic and economic traits were closer in LP than in QM. These results suggested that relationships between hydraulic and economic traits, hydraulic efficiency and safety played the role in constraining species distribution across regions. Interestingly, some relationships between traits changed (from significant correlation to non-correlation) in common species across two regions (from LP to QM), but not in endemic species. The change of these seven pairs of relationships might be a reason for common species' wide occurrence in the two forests with different soil water availability. In drought or humid conditions, congeneric species developed different types of adaptation mechanisms. The study helps to understand the environmental adaptive strategies of plant species, and the results improve our understanding of the role of both hydraulic and economic traits during community assembly.
水分有效性是影响植物物种分布的关键环境因素，而水力特性与经济特性之间的关系对于理解物种的分布格局很重要。然而，在相同群落类型但不同土壤水分有效性的情况下，同属物种之间的关系仍不明确。在中国西北部，秦岭（QM，湿润地区）和黄土高原（LP，干旱地区）的森林由于土壤水分有效性不同而具有不同的物种组成，但两个地区存在共有物种。我们分析了QM和LP森林中同属物种（包括共有物种和特有物种）的八个水力特性[气孔密度（SD）、叶脉密度（VD）、木材比重（WSG）、叶面积：边材面积（Al: As）、气孔长度（SL）、膨压损失点（Ψ）、最大导管直径（Vd）和树高（Height）]和五个经济特性[叶片干物质含量（LDMC）、叶组织密度（TD）、单位面积叶干质量（LMA）、叶厚度（LT）和最大净光合速率（P）]。我们探究了同属物种在不同地区是否具有不同的经济和水力特性。以及水力特性与经济特性之间的关系是否由土壤水分有效性决定，是否与同一群落的物种分布和同属特有物种组成有关。我们发现，LP物种的SD、VD、WSG、Al: As、SL、Ψ和Vd往往高于QM物种。在同属物种中，水力效率与安全性之间存在显著的权衡。此外，LP中水力特性与经济特性之间的关系比QM中更紧密。这些结果表明，水力特性与经济特性之间的关系、水力效率与安全性在限制跨区域物种分布方面发挥了作用。有趣的是，两个地区（从LP到QM）共有物种的一些特性之间的关系发生了变化（从显著相关变为不相关），但特有物种没有。这七对关系的变化可能是共有物种在具有不同土壤水分有效性的两个森林中广泛出现的一个原因。在干旱或湿润条件下，同属物种发展出了不同类型的适应机制。该研究有助于理解植物物种的环境适应策略，研究结果增进了我们对水力特性和经济特性在群落组装过程中作用的理解。
