Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, SP, 05508-090, Brazil.
Institute of Botany, Ulm University, Albert-Einstein-Allee 11, Ulm D-89081, Germany.
Ann Bot. 2024 Jul 9;134(2):337-350. doi: 10.1093/aob/mcae077.
Lianas have higher relative abundance and biomass in drier seasonal forests than in rainforests, but whether this difference is associated with their hydraulic strategies is unclear. Here, we investigate whether lianas of seasonally dry forests are safer and more efficient in water transport than rainforest lianas, explaining patterns of liana abundance.
We measured hydraulic traits on five pairs of congeneric lianas of the tribe Bignonieae in two contrasting forest sites: the wet 'Dense Ombrophilous Forest' in Central Amazonia (2 dry months) and the drier 'Semideciduous Seasonal Forest' in the inland Atlantic Forest (6 dry months). We also gathered a broader database, including 197 trees and 58 liana species from different tropical forests, to compare hydraulic safety between habits and forest types.
Bignonieae lianas from both forests had high and similar hydraulic efficiency but exhibited variability in resistance to embolism across forest types when phylogenetic relationships were taken into account. Three genera had higher hydraulic safety in the seasonal forest than in the rainforest, but species across both forests had similar positive hydraulic safety margins despite lower predawn water potential values of seasonal forest lianas. We did not find the safety-efficiency trade-off. Merging our results with previously published data revealed a high variability of resistance to embolism in both trees and lianas, independent of forest types.
The high hydraulic efficiency of lianas detected here probably favours their rapid growth across tropical forests, but differences in hydraulic safety highlight that some species are highly vulnerable and may rely on other mechanisms to cope with drought. Future research on the lethal dehydration threshold and the connection between hydraulic resistance strategies and liana abundance could offer further insights into tropical forest dynamics under climatic threats.
藤本植物在季节性干燥森林中的相对丰度和生物量都高于雨林,但这种差异是否与其水力策略有关尚不清楚。在这里,我们研究了季节性干燥森林中的藤本植物在水分运输方面是否比雨林藤本植物更安全、更高效,从而解释藤本植物丰度的模式。
我们在两个具有对比性的森林地点(亚马逊中部湿润的“茂密湿性森林”(约 2 个月的干燥期)和内陆大西洋森林较干燥的“半落叶季节性森林”(约 6 个月的干燥期))对五个 Bignonieae 族的同源藤本植物进行了水力特征测量。我们还收集了一个更广泛的数据库,包括来自不同热带森林的 197 棵树和 58 种藤本植物,以比较不同习性和森林类型之间的水力安全性。
来自两个森林的 Bignonieae 藤本植物具有较高且相似的水力效率,但当考虑到系统发育关系时,它们在对栓塞的抗性方面表现出跨森林类型的变异性。三个属在季节性森林中的水力安全性高于雨林,但跨两个森林的物种尽管季节性森林藤本植物的黎明前水势值较低,但仍具有相似的正水力安全裕度。我们没有发现安全性-效率权衡。将我们的结果与以前发表的数据合并表明,树木和藤本植物的栓塞抗性具有高度的可变性,与森林类型无关。
这里检测到的藤本植物的高水力效率可能有利于它们在热带森林中快速生长,但水力安全性的差异表明,一些物种非常脆弱,可能依赖于其他机制来应对干旱。未来对致死脱水阈值和水力阻力策略与藤本植物丰度之间的联系的研究可能会进一步深入了解热带森林在气候威胁下的动态。