Recent Growth and Expansion of Birch Shrubs Across a Low Arctic Landscape in Continental Canada: Are These Responses More a Consequence of the Severely Declining Caribou Herd than of Climate Warming?
Recent Growth and Expansion of Birch Shrubs Across a Low Arctic Landscape in Continental Canada: Are These Responses More a Consequence of the Severely Declining Caribou Herd than of Climate Warming?
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DOI：
10.1007/s10021-019-00474-7
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Grogan P
中科院分区：
文献类型：
--
作者：
Andruko R;Danby R;Grogan P
最近落叶灌木在北极大部分地区的广泛扩张主要归因于气候变暖。本研究调查了矮桦树（Betula glandulosa）在加拿大大陆内陆低北极地区的年代际生长率。对5种典型生境类型的白桦覆盖（100 m2重复样地）和个体灌木高度测量数据集进行了2006 - 2016年的比较，并对其环境特征进行了评价。此外，还根据20年气候记录评估了基于树木年代学的年增长率。桦树高度、横向尺寸和斑块地被盖度均比2006年增加了20 ~ 25%，但不同生境类型的增加幅度相似。总之，该地点最近变暖的证据有限，栖息地类型生长速率差异不明显，年度气候与茎次生生长之间缺乏相关性，这强烈表明气候变化不是主要原因。相反，我们认为在最近鹿群严重减少之后，驯鹿的释放可能解释了净灌木生长。灌木个体生长速率与土壤养分有效性相关，但土壤养分有效性变化较大，表明生长速率主要由细尺度而非生境尺度的养分供应空间异质性决定。总之，我们的研究结果表明，自2006年以来的十年里，在Daring Lake景观的各种栖息地类型中，桦树的生长都得到了增强，并表明最近北美驯鹿群的严重减少可能至少与气候变暖一样重要，因为气候变暖推动了加拿大中部低北极地区桦树灌木的扩张。本文的在线版本（10.1007/s10021-019-00474-7）包含补充资料，仅供授权用户使用。
The recent widespread expansion of deciduous shrubs across much of the Arctic has been largely attributed to climate warming. This study investigated decadal growth rates of dwarf birch (Betula glandulosa) across a low Arctic landscape in the continental interior of Canada. Detailed birch cover (100 m2 replicate plots) and individual shrub stature measurement datasets for five representative habitat-types were compared between 2006 and 2016, and evaluated in relation to environmental characteristics. Furthermore, dendrochronologically-based annual growth rates were assessed in relation to the 20-year climate record. Birch height, lateral dimensions, and patch groundcover all increased 20–25% relative to 2006 values, but these increases were similar among the habitat-types. Together, the limited evidence of recent warming at this site, the absence of significant habitat-type growth rate differences, and the lack of correlation between annual climate and stem secondary growth strongly suggest that climate change was not the principal cause. Instead, we propose that release from caribou impacts following the recent severe herd decline may explain the net shrub growth. Individual shrub growth rates were correlated with soil nutrient availability, but the latter was highly variable, suggesting that growth rates are primarily determined by fine-scale rather than habitat-scale spatial heterogeneity in nutrient supply. Together, our results demonstrate that birch growth has been enhanced across a variety of habitat-types in the Daring Lake landscape over the decade since 2006, and suggest that the recent severe caribou herd declines may be at least as significant as climate warming in driving birch shrub expansion in the Canadian central low Arctic. The online version of this article (10.1007/s10021-019-00474-7) contains supplementary material, which is available to authorized users.
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