Global vegetation biomass change (19882008) and attribution to environmental and human drivers
Global vegetation biomass change (19882008) and attribution to environmental and human drivers
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DOI：
10.1111/geb.12024
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发表时间：
2013-06-01
影响因子：
6.4
通讯作者：
de Jeu, Richard A. M.
中科院分区：
文献类型：
--
作者：
Liu, Yi Y.;van Dijk, Albert I. J. M.;de Jeu, Richard A. M.
目的植被光学厚度(VOD)是由被动微波遥感提取的陆地地上植被生物量中木质组分和叶组分的含水率指标。VOD不同于光学植被遥感数据，例如归一化差异植被指数，因为它：(A)在茂密的树冠上不容易饱和；(B)对光合作用和非光合作用的生物量都很敏感；以及(C)受大气条件的影响较小。我们的主要目标是分析最近开发的VOD长期记录，并调查1988至2008年间不同土地覆盖类型的植被水分含量如何应对环境变化和人类影响。全球定位。方法首先对年平均VOD进行曼肯德尔趋势检验，找出19882008年间VOD变化显著的地区。为了诊断观察到的变化的根本原因，进一步将这些已确定区域的模式与降水量、作物产量、森林砍伐和火灾发生的独立数据集进行了比较。结果(1)在草地和灌丛上，VOD与时间降雨型有很强的对应关系。(2)在农田上，年平均VOD表现出与报告的作物生产模式相对应的普遍增加，并归因于降水模式和农业改善的综合作用。(3)在湿润的热带森林上，VOD下降的空间格局与森林砍伐模式一致；2005年亚马逊干旱对应着VOD的暂时下降。(4)在北方森林上，区域VOD下降归因于火灾和砍伐的共同作用。主要结论VOD被动微波遥感可用于监测不同土地覆盖类型地上植被总量、含水率和生物量的全球变化。这一新的观测记录有助于水文、农业、生态和气候变化的研究，并为大规模植被变化及其驱动因素提供了新的见解。
Aim Vegetation optical depth (VOD) is an indicator of the water content of both woody and leaf components in terrestrial aboveground vegetation biomass that can be derived from passive microwave remote sensing. VOD is distinct from optical vegetation remote sensing data such as the normalized difference vegetation index in that it is: (a) less prone to saturation in dense canopies; (b) sensitive to both photosynthetic and non-photosynthetic biomass; and (c) less affected by atmospheric conditions. Our primary objective was to analyse a recently developed long-term VOD record and investigate how the vegetation water content of various land-cover types responded to environmental changes and human influences from 1988 to 2008. Location Global. Methods We first conducted MannKendall trend tests on annual average VOD to identify regions with significant changes over the period 19882008. To diagnose the underlying cause of the observed changes, patterns for these identified regions were further compared with independent datasets of precipitation, crop production, deforestation and fire occurrence. Results (1) Over grassland and shrubland, VOD patterns corresponded strongly to temporal precipitation patterns. (2) Over croplands, annual average VOD showed a general increase that corresponded to reported crop production patterns and was attributed to a combination of precipitation patterns and agricultural improvements. (3) Over humid tropical forest, the spatial pattern of VOD decline agrees well with deforestation patterns; the 2005 Amazon drought corresponded with a temporary VOD decrease. (4) Over boreal forests, regional VOD declines are attributed to a combination of fires and clear cutting. Main conclusions Passive microwave remote sensing of VOD can be used to monitor global changes in total aboveground vegetation water content and biomass over various land-cover types. This new observational record can help in hydrological, agricultural, ecological and climate change studies, and provides new insights into large-scale vegetation change and its drivers.