Moisture availability limits subalpine tree establishment
Moisture availability limits subalpine tree establishment
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DOI：
10.1002/ecy.2134
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发表时间：
2018-03-01
期刊：
影响因子：
4.8
通讯作者：
Veblen, Thomas T.
中科院分区：
文献类型：
--
作者：
Andrus, Robert A.;Harvey, Brian J.;Veblen, Thomas T.
在没有大规模干扰的情况下，许多温带针叶林只有在充足的种子生产与有利的气候相吻合时才能成功地建立幼苗。确定过去建立事件的频率和有利于幼苗建立的气候条件对于了解气候变暖如何影响未来树木建立事件的频率以及未来森林组成甚至森林覆盖的持续性至关重要。在美国落基山脉南部，对安格曼云杉（Picea engelmannii）和亚高山冷杉（Abies lasiocarpa）这两种在北美广泛分布的、共同出现的针叶树对气候变化的敏感性的研究集中在高山树线交错带，留下了这些物种在大部分海拔分布上的敏感性的不确定性。我们比较了每年的发芽日期>450恩格尔曼云杉和>500亚高山冷杉幼苗收集在一个复杂的地形，水分梯度的气候变化在科罗拉多前线范围。我们发现，安格曼云杉和亚高山冷杉建立episodically具有很强的同步性，在整个研究区域的建立事件。大规模的建立事件发生在土壤水分含量高的年份，其特点是高于平均水平的积雪和/或凉爽潮湿的夏季气候条件。在最近的一半的研究期间（1975-2010年），冷杉和云杉建立事件的数量减少，在他们的分布与积雪减少和几十年的趋势，夏季温度上升，水分亏缺增加。与预期和观察到的海洋亚高山森林中树木建立与气候变暖的增加相反，我们的研究结果表明，随着变暖导致水分亏缺增加，水分有限的亚高山树木范围的核心可能会出现招聘下降。
In the absence of broad-scale disturbance, many temperate coniferous forests experience successful seedling establishment only when abundant seed production coincides with favorable climate. Identifying the frequency of past establishment events and the climate conditions favorable for seedling establishment is essential to understanding how climate warming could affect the frequency of future tree establishment events and therefore future forest composition or even persistence of a forest cover. In the southern Rocky Mountains, USA, research on the sensitivity of establishment of Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa)two widely distributed, co-occurring conifers in North Americato climate variability has focused on the alpine treeline ecotone, leaving uncertainty about the sensitivity of these species across much of their elevation distribution. We compared annual germination dates for >450 Engelmann spruce and >500 subalpine fir seedlings collected across a complex topographic-moisture gradient to climate variability in the Colorado Front Range. We found that Engelmann spruce and subalpine fir established episodically with strong synchrony in establishment events across the study area. Broad-scale establishment events occurred in years of high soil moisture availability, which were characterized by above-average snowpack and/or cool and wet summer climatic conditions. In the recent half of the study period (1975-2010), a decrease in the number of fir and spruce establishment events across their distribution coincided with declining snowpack and a multi-decadal trend of rising summer temperature and increasing moisture deficits. Counter to expected and observed increases in tree establishment with climate warming in maritime subalpine forests, our results show that recruitment declines will likely occur across the core of moisture-limited subalpine tree ranges as warming drives increased moisture deficits.