The creation of alternative stable states in the southern boreal forest, Quebec, Canada
The creation of alternative stable states in the southern boreal forest, Quebec, Canada
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DOI：
10.1890/04-1621
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发表时间：
2005-11-01
影响因子：
6.1
通讯作者：
Payette, S
中科院分区：
文献类型：
--
作者：
Jasinski, JPP;Payette, S
加拿大魁北克大花园公园最南端的云杉地衣林地位于北方地衣林地带的通常分布范围以南500 km处。它们在云杉苔藓森林基质中的共存表明存在替代稳定状态。我们调查的可能性，这些云杉地衣林地作为一个替代的稳定状态沿着的因素，有助于他们的起源和时空分布。分析植物mnacrofossils，木炭，头胶囊落叶昆虫，花粉被用来沿着植被调查重建过去和现在的干扰动态沿着东西向的样带，对应于降水和火灾频率梯度。在每个站点，云杉芽虫头胶囊被发现之前的木炭层划定转移到云杉地衣林地，证明复合干扰（昆虫火灾）的地衣林地的起源。苔藓森林以前占据了所有的地衣林地，最古老的记录始于约。8300-9400年BP。在公园的地衣林地区，2500年BP左右的火灾频率较高的变化是显而易见的。较低的火灾频率西部的地衣林地区可能是地形降水的结果。虽然云杉芽虫影响整个地区，地衣林地被发现专门在火灾频率增加的区域。因此，正是这两种干扰因素的叠加，才导致了它们的产生和空间分布。地衣林地成立日期范围580和1440年BP之间，表明这些地衣林地一直保持开放的结构，随着时间的推移，并没有转化为封闭的森林。他们的持久性，沿着与他们以前的苔藓森林的历史和目前发生在封闭的苔藓森林附近，表明他们是一个替代的稳定状态的云杉苔藓森林，而不是一个演替阶段。与报告的其他替代稳定状态的例子相比，这一情况是系统固有的自然扰动而不是人为影响的结果。
The southernmost spruce-lichen woodlands in the Parc des Grands-Jardins, Quebec, Canada, are situated 500 km south of their usual range in the northern lichen woodland zone. Their co-occurrence within a spruce-moss forest matrix suggests the existence of alternative stable states. We investigate the possibility of these spruce-lichen woodlands as an alternative stable state along with the factors contributing to their origin and spatiotemporal distribution. Analysis of plant rnacrofossils, charcoal, head capsules of defoliating insects, and pollen were used along with vegetation surveys to reconstruct the past and present disturbance dynamics along an east-west transect, corresponding to a precipitation and fire frequency gradient. At each site, spruce budworm head capsules were found preceding the charcoal layer delineating the shift to spruce-lichen woodland, demonstrating the compound disturbance (insect-fire) origin of the lichen woodlands. Moss forests previously occupied all lichen woodland sites, with the oldest record starting ca. 8300-9400 yr BP. A change to a higher fire frequency around 2500 yr BP was evident in the lichen woodland zone of the park. A lower fire frequency west of the lichen woodland zone likely is a result of orographic precipitation. While the spruce budworm affects the entire region, lichen woodlands are found exclusively within an increased fire frequency zone. Thus, it is the superimposition of these two disturbance factors that is responsible both for their creation and spatial distribution. Lichen woodland inception dates range between 580 and 1440 yr BP, demonstrating that these lichen woodlands have maintained their open structure with time and have not transformed into closed forests. Their persistence, along with their previous moss forest histories and current occurrence adjacent to closed moss forests, indicate that they are an alternative stable state to the spruce-moss forests and not a successional stage. In contrast to other examples of reported alternative stable states, this one is a result of natural disturbances inherent to the system and not anthropogenic impacts.