Department of Community Ecology, Helmholtz Centre for Environmental Research - UFZ, Theodor-Lieser-Straße 4, 06120, Halle (Saale), Germany.
German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, 04103, Leipzig, Germany.
Ecology. 2019 May;100(5):e02666. doi: 10.1002/ecy.2666. Epub 2019 Apr 8.
Hydraulic traits are important for woody plant functioning and distribution. Associations among hydraulic traits, other leaf and stem traits, and species' performance are relatively well understood for trees, but remain poorly studied for lianas. We evaluated the coordination among hydraulic efficiency (i.e., maximum hydraulic conductivity), hydraulic safety (i.e., cavitation resistance), a suite of eight morphological and physiological traits, and species' abundances for saplings of 24 liana species and 27 tree species in wet tropical forests in Panama. Trees showed a strong trade-off between hydraulic efficiency and hydraulic safety, whereas efficiency and safety were decoupled in lianas. Hydraulic efficiency was strongly and similarly correlated with acquisitive traits for lianas and trees (e.g., positively with gas exchange rates and negatively with wood density). Hydraulic safety, however, showed no correlations with other traits in lianas, but with several in trees (e.g., positively with leaf dry matter content and wood density and negatively with gas exchange rates), indicating that in lianas hydraulic efficiency is an anchor trait because it is correlated with many other traits, while in trees both efficiency and safety are anchor traits. Traits related to shade tolerance (e.g., low specific leaf area and high wood density) were associated with high local tree sapling abundance, but not with liana abundance. Our results suggest that different, yet unknown mechanisms determine hydraulic safety and local-scale abundance for lianas compared to trees. For trees, the trade-off between efficiency and safety will provide less possibilities for ecological strategies. For lianas, however, the uncoupling of efficiency and safety could allow them to have high hydraulic efficiency, and hence high growth rates, without compromising resistance to cavitation under drought, thus allowing them to thrive and outperform trees under drier conditions.
水力特性对木本植物的功能和分布至关重要。树木的水力特性与其他叶片和茎干特性以及物种表现之间的关联已得到较为充分的研究，但藤本植物的此类关联仍研究甚少。我们评估了巴拿马潮湿热带森林中 24 种藤本植物和 27 种木本植物幼树的水力效率（即最大水力导度）、水力安全性（即抗空化性）、8 种形态和生理特性以及物种丰度之间的协调性。树木表现出水力效率和水力安全性之间的强烈权衡，而藤本植物的效率和安全性则是解耦的。水力效率与藤本植物和树木的获取性状强烈且相似相关（例如，与气体交换速率呈正相关，与木材密度呈负相关）。然而，水力安全性与藤本植物的其他性状没有相关性，但与树木的几个性状有相关性（例如，与叶干物质含量、木材密度呈正相关，与气体交换速率呈负相关），这表明在藤本植物中，水力效率是一种锚定性状，因为它与许多其他性状相关，而在树木中，效率和安全性都是锚定性状。与耐荫性相关的性状（例如，低比叶面积和高木材密度）与当地树木幼树的丰富度有关，但与藤本植物的丰富度无关。我们的结果表明，与树木相比，不同的、未知的机制决定了藤本植物的水力安全性和局部丰度。对于树木来说，效率和安全性之间的权衡将为生态策略提供较少的可能性。然而，对于藤本植物来说，效率和安全性的解耦可以使它们具有较高的水力效率，从而具有较高的生长速率，而不会在干旱条件下损害抗空化性，从而使它们在较干燥的条件下茁壮成长并胜过树木。
