Arctic greening associated with lengthening growing seasons in Northern Alaska
Arctic greening associated with lengthening growing seasons in Northern Alaska
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DOI：
10.1088/1748-9326/ab5e26
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发表时间：
2019-12-01
影响因子：
6.7
通讯作者：
Zona, Donatella
中科院分区：
文献类型：
--
作者：
Arndt, Kyle A.;Santos, Maria J.;Zona, Donatella
许多研究报告说，北极正在绿化;然而，我们缺乏对导致这种观察到的绿化的详细模式和过程的了解。归一化差异植被指数被用来量化绿化情况，过去几十年来，在泛北极地区使用诸如高级甚高分辨率辐射计或中分辨率成像分光仪等低空间分辨率卫星图像，绿化情况基本上呈积极趋势。然而，在北极地区大量的细尺度空间异质性使得这种大规模的调查很难解释植被和其他环境变化。在这里，我们专注于北方阿拉斯加北极地区的一个区域，使用DigitalGlobe（TM）的高空间分辨率（4米）多光谱卫星图像来分析2002年至2016年14年间Utqiagvik（以前称为巴罗）附近的绿化趋势。我们发现，苔原植被已经绿化（tau = 0.65，p = 0.01，NDVI增加0.01年（-1）），尽管没有整体变化的植被群落组成。绿化与解冻度日数最密切相关（R-2 = 0.77，F = 21.5，p < 0.001），在14年的研究期间，解冻度日数以类似的线性趋势增加（1.79.+/-. 0.50天/年，p < 0.01，τ = -0.56）。这表明，在这个北极生态系统中，由于生长季节的延长，绿色正在发生，这似乎刺激了植物生产力，而植被群落没有任何显着变化。我们发现，在潮湿的地方，植被群落变绿的速度是在干燥条件下发现的植被群落变绿的速度的两倍，这支持了这些群落对变暖反应更强烈的假设。我们认为，在北极环境中，植被生产力可能会继续上升，特别是在潮湿地区。
Many studies have reported that the Arctic is greening; however, we lack an understanding of the detailed patterns and processes that are leading to this observed greening. The normalized difference vegetation index (NDVI) is used to quantify greening, which has had largely positive trends over the last few decades using low spatial resolution satellite imagery such as AVHRR or MODIS over the pan-Arctic region. However, substantial fine scale spatial heterogeneity in the Arctic makes this large-scale investigation hard to interpret in terms of vegetation and other environmental changes. Here we focus on one area of the northern Alaskan Arctic using high spatial resolution (4m) multispectral satellite imagery from DigitalGlobe (TM) to analyze the greening trend near Utqiagvik (formerly known as Barrow) over 14 years from 2002 to 2016. We found that tundra vegetation has been greening (tau = 0.65, p = 0.01, NDVI increase of 0.01 yr(-1)) despite no overall change in vegetation community composition. The greening is most closely correlated to the number of thawing degree days (R-2 = 0.77, F = 21.5, p < 0.001) which increased in a similar linear trend over the 14 year study period (1.79.+/-.0.50 days per year, p < 0.01, tau = -0.56). This suggests that in this Arctic ecosystem, greening is occurring due to a lengthening growing season that appears to stimulate plant productivity without any significant change in vegetation communities. We found that vegetation communities in wetter locations greened about twice as fast as those found in drier conditions supporting the hypothesis that these communities respond more strongly to warming. We suggest that in Arctic environments, vegetation productivity may continue to rise, particularly in wet areas.