Zhu LiRong, Zhou Ting, Chen BaoMing, Peng ShaoLin
State Key Laboratory of Biocontrol, Key Laboratory of Biodiversity Dynamics and Conservation of Guangdong Higher Education Institutes, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510006, China.
Sci China Life Sci. 2015 May;58(5):472-9. doi: 10.1007/s11427-014-4722-2. Epub 2014 Oct 14.
The response and recovery mechanisms of forests to damage from freezing rain and snow events are a key topic in forest research and management. However, the relationship between the degree of damage and tree age, i.e., whether seedlings, young trees, or adult trees are most vulnerable, remains unclear and is rarely reported. We investigated the effect of tree age on the degrees of vegetation damage and subsequent recovery in three subtropical forest types-coniferous, mixed, and broad-leaved-in the Tianjing Mountains, South China, after a series of rare icy rain and freezing snow events in 2008. The results showed that damage and recovery rates were both dependent on tree age, with the proportion of damaged vegetation increasing with age (estimated by diameter at breast height, DBH) in all three forest types and gradually plateauing. Significant variation occurred among forest types. Young trees in the coniferous forest were more vulnerable than those in the broad-leaved forest. The type of damage also varied with tree age in different ways in the three forest types. The proportion of young seedlings that were uprooted (the most severe type of damage) was highest in the coniferous forest. In the mixed forest, young trees were significantly more likely to be uprooted than seedlings and adult trees, while in the broad-leaved forest, the proportion of uprooted adult trees was significantly higher than that of seedlings and young trees. There were also differences among forest types in how tree age affected damage recovery. In the coniferous forest, the recovery rate of trees with broken trunks or crowns (DBH > 2.5 cm) increased with tree age. However, in the mixed and broad-leaved forests, no obvious correlation between the recovery rate of trees with broken trunks or crowns and tree age was observed. Trees with severe root damage did not recover; they were uprooted and died. In these forests, vegetation damage and recovery showed tree age dependencies, which varied with tree shape, forest type, and damage type. Understanding this dependency will guide restoration after freezing rain and snow disturbances.
森林对冻雨和雪灾的响应及恢复机制是森林研究与管理中的关键课题。然而，损害程度与树龄之间的关系，即幼苗、幼树或成年树中哪类最易受损，仍不明确且鲜有报道。我们研究了树龄对中国南方天井山三种亚热带森林类型（针叶林、混交林和阔叶林）植被损害程度及后续恢复的影响，这是在2008年一系列罕见的冻雨和暴雪事件之后进行的。结果表明，损害率和恢复率均取决于树龄，在所有三种森林类型中，受损植被比例随树龄（以胸径，即DBH估算）增加而上升，并逐渐趋于平稳。不同森林类型间存在显著差异。针叶林中的幼树比阔叶林中的更易受损。在三种森林类型中，损害类型也因树龄而异。针叶林中被连根拔起（最严重的损害类型）的幼苗比例最高。在混交林中，幼树比幼苗和成年树更易被连根拔起，而在阔叶林中，成年树被连根拔起的比例显著高于幼苗和幼树。树龄对损害恢复的影响在不同森林类型间也存在差异。在针叶林中，树干或树冠受损（DBH > 2.5 cm）的树木恢复率随树龄增加。然而，在混交林和阔叶林中，未观察到树干或树冠受损树木的恢复率与树龄之间有明显相关性。根系严重受损的树木无法恢复；它们被连根拔起并死亡。在这些森林中，植被损害和恢复呈现出树龄依赖性，这种依赖性因树型、森林类型和损害类型而异。了解这种依赖性将为冻雨和雪灾干扰后的恢复提供指导。
