Research Centre for Applied Alpine Ecology, La Trobe University, Bundoora Victoria, Australia.
Department of Ecology, Environment and Evolution, La Trobe University, Bundoora Victoria, Australia.
PLoS One. 2020 Apr 10;15(4):e0231339. doi: 10.1371/journal.pone.0231339. eCollection 2020.
How species respond to climate change will depend on biological characteristics, species physiological limits, traits (such as dispersal), and interactions with disturbance. We examine multi-decadal shifts in the distribution of trees at the alpine treeline in response to regional warming and repeated disturbance by fire in the Victorian Alps, south-east Australia. Alpine treelines are composed of Eucalyptus pauciflora subsp. niphophila (Snow Gum, Myrtaceae) species. The location and basal girth of all trees and saplings were recorded across treelines at four mountains in 2002 and 2018. We quantify changes in treeline position (sapling recruitment above treeline) over time in relation to warming and disturbance by fire, and examine changes in stand structure below treeline (stand density, size class analyses). Short-distance advance of the treeline occurred between 2002 and 2018, but was largely restricted to areas that were unburned during this period. No saplings were seen above treeline after two fires, despite evidence that saplings were common pre-fire. Below treeline, subalpine woodland stands were largely resilient to fire; trees resprouted from lignotubers. However, small trees were reduced in number in woodlands when burned twice within a decade. Population dynamics at the alpine treeline were responsive to recent climate change, but other factors (e.g. disturbance) are crucial to understand recruitment trends. Establishment of saplings above treeline was largely restricted to unburned areas. These results indicate fire is a strong demographic filter on treeline dynamics; there is a clear need to frame alpine treeline establishment processes beyond just being a response to climate warming. Long lag periods in treeline change may be expected where recurrent disturbance is a feature of the landscape.
物种对气候变化的反应将取决于生物特征、物种生理极限、特征（如扩散）以及与干扰的相互作用。我们研究了澳大利亚东南部维多利亚阿尔卑斯山树木分布在多十年时间内的变化，以响应区域变暖以及火灾的反复干扰。高山树线由桉树少花亚种组成。niphophila（雪胶，桃金娘科）物种。2002 年和 2018 年，在四座山上的树线附近记录了所有树木和幼树的位置和基围。我们量化了随着时间的推移，树线位置（树线以上的幼树招募）的变化与变暖以及火灾干扰之间的关系，并研究了树线以下林分结构的变化（林分密度、大小类分析）。2002 年至 2018 年间，树线短距离前进，但主要限于该期间未被烧毁的区域。尽管有证据表明火灾前幼树很常见，但两次火灾后，树线以上仍未发现幼树。在树线以下，亚高山林地林分对火灾具有很强的弹性；树木从木质部再生。然而，在十年内两次燃烧后，林地中小树的数量减少了。高山树线的种群动态对最近的气候变化有反应，但其他因素（例如干扰）对于理解招募趋势至关重要。在树线以上建立幼树主要限于未燃烧的区域。这些结果表明，火灾是树线动态的一个强大的人口过滤器；明确需要超越仅仅对气候变暖的反应来构建高山树线建立过程。如果反复发生干扰是景观的一个特征，那么预计树线变化的滞后时间会很长。
