Vulnerability of Amazonian forests to repeated droughts
Vulnerability of Amazonian forests to repeated droughts
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DOI：
10.1098/rstb.2017.0411
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发表时间：
2018-11-19
影响因子：
6.3
通讯作者：
Oliveira e Cruz de Aragao, Luiz Eduardo
中科院分区：
文献类型：
--
作者：
Anderson, Liana Oighenstein;Neto, Germano Ribeiro;Oliveira e Cruz de Aragao, Luiz Eduardo
在过去的几十年里，极端干旱在亚马逊地区反复出现，造成了社会经济和环境影响。在这里，我们调查了亚马逊森林的脆弱性，包括未受干扰的和人为修改的，反复干旱。我们将脆弱性定义为(i)暴露度，即这些生态系统暴露于干旱的程度；（ii）敏感性，即干旱对遥感得出的森林绿化率的影响程度。利用标准化降水指数（SPI）和与植被水分胁迫相关的最大累积亏水（MCWD）对1981 - 2016年的气象干旱进行评估，计算暴露量。基于2003 - 2016年新获得的中分辨率成像光谱仪(MODIS)/多角度大气校正算法（MAIAC）产品的增强型植被指数异常（AEVI），对森林光合能力的敏感性进行了评估。我们估计，根据SPI测量，2015/2016年巴西亚马逊生物群落的46%处于严重至极端干旱状态，而2009/2010年和2004/2005年的干旱分别为16%和8%。最近的干旱（2015/2016）影响了自1981年干旱以来最大的地区。基于最小和最大AEVI分析，干旱会增加亚马逊森林光合能力的差异。然而，光合能力下降的区域在信号中占主导地位，超过40万km(2)的森林，比AEVI增强的区域大4个数量级。2005 - 2016年，负AEVI强度稳步上升。这些结果表明，在分析期间，干旱影响随着时间的推移而加剧。21世纪的森林越来越容易受到干旱的影响，面积更大的森林对该区域的缺水作出了强烈和消极的反应。本文是讨论会议“2015/2016年厄尔尼诺现象对陆地热带碳循环的影响：模式、机制和影响”的一部分。
Extreme droughts have been recurrent in the Amazon over the past decades, causing socio-economic and environmental impacts. Here, we investigate the vulnerability of Amazonian forests, both undisturbed and human-modified, to repeated droughts. We defined vulnerability as a measure of (i) exposure, which is the degree to which these ecosystems were exposed to droughts, and (ii) its sensitivity, measured as the degree to which the drought has affected remote sensing-derived forest greenness. The exposure was calculated by assessing the meteorological drought, using the standardized precipitation index (SPI) and the maximum cumulative water deficit (MCWD), which is related to vegetation water stress, from 1981 to 2016. The sensitivity was assessed based on the enhanced vegetation index anomalies (AEVI), derived from the newly available Moderate Resolution Imaging Spectroradiometer (MODIS)/Multi-Angle Implementation of Atmospheric Correction algorithm (MAIAC) product, from 2003 to 2016, which is indicative of forest's photosynthetic capacity. We estimated that 46% of the Brazilian Amazon biome was under severe to extreme drought in 2015/2016 as measured by the SPI, compared with 16% and 8% for the 2009/2010 and 2004/2005 droughts, respectively. The most recent drought (2015/2016) affected the largest area since the drought of 1981. Droughts tend to increase the variance of the photosynthetic capacity of Amazonian forests as based on the minimum and maximum AEVI analysis. However, the area showing a reduction in photosynthetic capacity prevails in the signal, reaching more than 400 000 km(2) of forests, four orders of magnitude larger than areas with AEVI enhancement. Moreover, the intensity of the negative AEVI steadily increased from 2005 to 2016. These results indicate that during the analysed period drought impacts were being exacerbated through time. Forests in the twenty-first century are becoming more vulnerable to droughts, with larger areas intensively and negatively responding to water shortage in the region.This article is part of a discussion meeting issue 'The impact of the 2015/2016 El Nino on the terrestrial tropical carbon cycle: patterns, mechanisms and implications'.