Fine-Scale NDVI Reconstruction Back to 1906 from Tree-Rings in the Greater Yellowstone Ecosystem
Fine-Scale NDVI Reconstruction Back to 1906 from Tree-Rings in the Greater Yellowstone Ecosystem
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DOI：
10.3390/f12101324
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发表时间：
2021-09
期刊：
影响因子：
2.9
通讯作者：
Hang Li;Ichchha Thapa;J. Speer
中科院分区：
文献类型：
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作者：
Hang Li;Ichchha Thapa;J. Speer
全球变暖和相关的干扰，如干旱，水和热应力，正在造成森林减少，导致政权转移。传统的研究结合树轮宽度（TRW）和归一化植被指数（NDVI）来重建NDVI值，忽略了混合土地覆盖的影响。利用622幅Landsat卫星影像和15块样地的树芯数据，建立了TRW-NDVI模型，并采用逐点回归方法重建了年NDVI图。我们的模型在研究区域表现良好，如排除水和贫瘠区域的71.14%（p < 0.05）的区域的显著重建所证明的。用常规方法重建的NDVI与本文方法重建的NDVI之间的误差率可达10.36%。30 m分辨率重建的近百年NDVI图像清晰地显示了植被密度的下降，并检测到从1906年到2015年长达数十年的制度转变。我们的研究地点经历了五次政权转移，特别是在20世纪30年代和50年代，这是北美的特大干旱。有了高分辨率的地图，可以每年在百年尺度上观察到政权转变。它们也可以用来了解黄石公园的生态系统是如何在上个世纪随着其生态遗产而逐渐改变的。
Global warming and related disturbances, such as drought, water, and heat stress, are causing forest decline resulting in regime shifts. Conventional studies have combined tree-ring width (TRW) and the normalized difference vegetation index (NDVI) to reconstruct NDVI values and ignored the influences of mixed land covers. We built an integrated TRW-NDVI model and reconstructed the annual NDVI maps by using 622 Landsat satellite images and tree cores from 15 plots using point-by-point regression. Our model performed well in the study area, as demonstrated by significant reconstructions for 71.14% (p < 0.05) of the area with the exclusion of water and barren areas. The error rate between the reconstructed NDVI using the conventional approach and our approach could reach 10.36%. The 30 m resolution reconstructed NDVI images in the recent 100 years clearly displayed a decrease in vegetation density and detected decades-long regime shifts from 1906 to 2015. Our study site experienced five regime shifts, markedly the 1930s and 1950s, which were megadroughts across North America. With fine resolution maps, regime shifts could be observed annually at the centennial scale. They can also be used to understand how the Yellowstone ecosystem has gradually changed with its ecological legacies in the last century.