A narrow window of summer temperatures associated with shrub growth in Arctic Alaska
A narrow window of summer temperatures associated with shrub growth in Arctic Alaska
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DOI：
10.1088/1748-9326/ab897f
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发表时间：
2020-10-01
影响因子：
6.7
通讯作者：
D'Arrigo, Rosanne
中科院分区：
文献类型：
--
作者：
Andreu-Hayles, Laia;Gaglioti, Benjamin, V;D'Arrigo, Rosanne
近几十年来的变暖引发了北极和高山苔原的灌木扩张，这正在改变这些温度有限的生态系统，改变碳和养分循环，火灾制度，永久冻土稳定性，地表气候反馈和野生动物栖息地。未来北极灌木丛扩张的地点和时间将部分取决于不同的灌木群落对气温变暖的反应。在这里，我们分析了一个灌木环宽度网络的18个网站组成的柳属。和Alnus viridisgrowing横跨阿拉斯加北坡（68-71度N; 164-149度W），以评估灌木的温度敏感性，并比较自1982年以来的卫星NDVI（归一化差异植被指数）数据的径向生长模式。无论立地条件和分类群如何，所有灌木都有一个共同的逐年生长变异性，并且对大约10年以来的每日最高气温（Tmax）有积极的反应。5月31日（即Tmax类似于6摄氏度）至7月初（即Tmax类似于12摄氏度），其中三分之二为显著相关。因此，6月份的灌木生长温度的敏感性最高。这一时期的温度和物候绿色的季节性增加相吻合的实地观测和季节性周期的植被指数（光合活性的代理）表明北坡。几乎所有的抽样灌木（98%）开始他们的增长后，1960年，74%自1980年开始。1980年后的灌木补充脉冲与6月气温比以往同期高出2摄氏度，以及灌木断面积增量和夏季NDVI峰值的积极趋势相吻合。灌木生长和夏季高峰期NDVI之间的显着相关性表明，这些径向生长模式在灌木反映苔原生产力在更广泛的规模和阿拉斯加北坡苔原植被经历了绿化的趋势在1980年和2012年之间。
Warming in recent decades has triggered shrub expansion in Arctic and alpine tundra, which is transforming these temperature-limited ecosystems and altering carbon and nutrient cycles, fire regimes, permafrost stability, land-surface climate-feedbacks, and wildlife habitat. Where and when Arctic shrub expansion happens in the future will depend in part on how different shrub communities respond to warming air temperatures. Here, we analyze a shrub ring-width network of 18 sites consisting ofSalixspp. andAlnus viridisgrowing across the North Slope of Alaska (68-71 degrees N; 164-149 degrees W) to assess shrub temperature sensitivity and compare radial growth patterns with satellite NDVI (normalized difference vegetation index) data since 1982. Regardless of site conditions and taxa, all shrubs shared a common year-to-year growth variability and had a positive response to daily maximum air temperatures (Tmax) from ca. May 31 (i.e. Tmax similar to 6 degrees C) to early July (i.e. Tmax similar to 12 degrees C), two-thirds of which were significant correlations. Thus, the month of June had the highest shrub growth-temperature sensitivity. This period coincides with the seasonal increase in temperature and phenological green up on the North Slope indicated by both field observations and the seasonal cycle of NDVI (a proxy of photosynthetic activity). Nearly all of the sampled shrubs (98%) initiated their growth after 1960, with 74% initiated since 1980. This post-1980 shrub-recruitment pulse coincided with similar to 2 degrees C warmer June temperatures compared to prior periods, as well as with positive trends in shrub basal area increments and peak summer NDVI. Significant correlations between shrub growth and peak summer NDVI indicate these radial growth patterns in shrubs reflect tundra productivity at a broader scale and that tundra vegetation on the North Slope of Alaska underwent a greening trend between 1980 and 2012.