Regional‐scale forest restoration effects on ecosystem resiliency to drought: a synthesis of vegetation and moisture trends on Google Earth Engine
Regional‐scale forest restoration effects on ecosystem resiliency to drought: a synthesis of vegetation and moisture trends on Google Earth Engine
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DOI：
10.1002/rse2.186
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发表时间：
2020-11
影响因子：
5.5
通讯作者：
T. Sankey;Adam Belmonte;R. Massey;J. Leonard
中科院分区：
文献类型：
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作者：
T. Sankey;Adam Belmonte;R. Massey;J. Leonard
整个北美西部森林结构和生态功能的大规模变化导致野火的频率，规模和严重程度增加。美国林务局正在实施全州范围的森林恢复计划，以减少野火危害并改善森林健康。我们提供了亚利桑那州1990年至2017年处理前和处理后森林植被和生态系统水分趋势的综合，亚利桑那州是美国第一个在350万公顷的1,200多个多边形区域实施各种间伐和燃烧方法的州。使用Google Earth Engine上的4，426张Landsat卫星图像，我们计算了归一化差异水分指数（NNDW），归一化差异水分指数（NDWI）和归一化差异植被指数（NDVI），以创建密集的时间序列数据集。然后使用Mann-Kendall tau检验对指数和1990 - 2017年的年总降水量数据集进行检查，以确定每个像素的统计学显著性上升和下降趋势。我们的研究结果表明，大部分的研究区域都经历了干旱条件恢复治疗和NDVI值显着下降，特别是在干燥的春季。然而，NNDWI和NNDWI趋势都表明，森林恢复处理有助于增加总生态系统水分，而处理后期间的降水量呈现稳定的趋势。森林恢复处理似乎改善了森林的整体健康和抗旱能力，特别是在干旱的春季，当森林最容易受到水压力和野火风险。我们对这些变量的空间模式和长期趋势的研究结果可以为目前正在进行和未来的修复治疗提供信息，以更好地针对美国西南部的治疗策略。Google Earth Engine使我们能够综合大区域的这些长期趋势，并将在未来十年加强我们的持续监测。
Large‐scale changes in forest structure and ecological function throughout western North America have led to increased frequency, size, and severity of wildfires. The US Forest Service is implementing state‐wide forest restoration initiatives to reduce wildfire hazards and improve forest health. We provide a synthesis of pre‐ and post‐treatment forest vegetation and ecosystem moisture trends between 1990 and 2017 in Arizona, the first US state where the initiative has implemented a variety of thinning and burning methods in over 1,200 polygon areas across 3.5 million ha. Using 4,426 Landsat satellite images on Google Earth Engine, we calculated normalized difference moisture index (NDMI), normalized difference water index (NDWI), and normalized difference vegetation index (NDVI) to create dense time‐series datasets. The indices and 1990‐2017 annual total precipitation dataset were then examined using a Mann–Kendall tau test to identify statistically significant upward and downward trends for each pixel. Our results indicate that much of the study region were experiencing drought conditions prior to restoration treatments and NDVI values were significantly decreasing, especially during the dry spring season. However, both NDMI and NDWI trends indicate that the forest restoration treatments have contributed to increased total ecosystem moisture, while precipitation in the post‐treatment period exhibit stable trends. Forest restoration treatments appear to have improved the overall forest health and resiliency to drought, especially during the dry spring season, when forests are most vulnerable to water stress and wildfire risks. Our results of the spatial patterns and long‐term trends in these variables can inform the currently ongoing and future restoration treatments to better target the treatment strategy across the southwestern USA. Google Earth Engine enabled our synthesis of these long‐term trends over the large region and will enhance our continued monitoring in the coming decade.