Lab of Vegetation Ecology, Universidade Estadual Paulista (UNESP), Instituto de Biociências, Avenida 24-A, 1515, Rio Claro, 13506-900, Brazil.
AMAP, Univ Montpellier, CIRAD, CNRS, INRAE, IRD, Montpellier, France.
Ann Bot. 2023 Apr 28;131(4):613-621. doi: 10.1093/aob/mcad014.
Bark allows species to survive fire, protecting their inner tissues and allowing new branches to resprout from aerial buds. Thus, bark production is likely to be selected with aerial bud protection in fire-prone ecosystems. By considering the coexistence of fire-prone and fire-free ecosystems, in addition to the different impacts of flames on different growth forms, in this study we tested whether: (1) species from areas with higher fire frequencies have a faster bark production; (2) bark growth rate differs between trees and shrubs; (3) generalists adjust their bark production according to their environment (fire-prone or fire-free ecosystems); and (4) fast bark production results in better aerial bud protection.
We sampled two different types of forests and savannas in the Cerrado and registered every woody individual with height between 1.5 and 3 m tall (directly exposed to the flames). For the 123 species registered, we sampled three different individuals in each vegetation type where the species occurred to assess their bark production and aerial bud protection. We then checked, for each species, their preferred habitat (savanna and forest specialists or generalists) and their predominant growth form.
A minimal threshold of 0.13 mm per growth unit of bark production differentiated woody communities from savannas and forests. Shrubs and trees did not differ in terms of bark growth rate, despite being exposed to the flames in a different manner. Generalist species in savannas were able to produce bark above the threshold. However, when these species were in forests they produced bark below the threshold. Finally, a higher bark growth rate accounted for a better aerial bud protection.
Generalist species are likely to be capable of displaying plasticity in their bark production, which could be important for their success in contrasting ecosystems. The relationship between aerial bud protection and bark growth rate suggests that bark production plays an important role in protecting the dormant buds, in addition to being selected in fire-prone ecosystems.
树皮使物种能够在火灾中存活，保护其内部组织，并允许新的树枝从空中芽中重新萌发。因此，在易发生火灾的生态系统中，树皮的产生很可能与空中芽的保护一起被选择。通过考虑到易发生火灾和无火灾的生态系统的共存，以及火焰对不同生长形式的不同影响，本研究测试了以下几点：（1）来自火灾频率较高地区的物种是否具有更快的树皮产生速度；（2）树皮生长速度在树木和灌木之间是否存在差异；（3）广食性物种是否根据其环境（易发生火灾或无火灾的生态系统）调整其树皮产生；（4）快速的树皮产生是否能更好地保护空中芽。
我们在塞拉多（Cerrado）采样了两种不同类型的森林和热带稀树草原，并记录了每一个高度在 1.5 到 3 米之间（直接暴露在火焰下）的木本个体。对于登记的 123 个物种，我们在每个物种出现的植被类型中采样了三个不同的个体，以评估它们的树皮产生和空中芽保护。然后，我们检查了每个物种的首选栖息地（热带稀树草原和森林专家或广食性物种）和其主要生长形式。
树皮产生的最小阈值为 0.13 毫米/生长单位，可将木本群落与热带稀树草原和森林区分开来。尽管灌木和树木暴露在火焰中的方式不同，但它们的树皮生长速度没有差异。热带稀树草原的广食性物种能够产生高于阈值的树皮。然而，当这些物种处于森林中时，它们产生的树皮低于阈值。最后，较高的树皮生长速度可以更好地保护空中芽。
广食性物种可能具有在树皮产生方面的可塑性，这对它们在不同生态系统中的成功可能很重要。空中芽保护和树皮生长速度之间的关系表明，树皮产生除了在易发生火灾的生态系统中被选择外，还在保护休眠芽方面发挥了重要作用。
