Arid
DOI10.1016/j.rse.2013.09.011
Re-greening Sahel: 30 years of remote sensing data and field observations (Mali, Niger)
Dardel, C.1; Kergoat, L.1; Hiernaux, P.1; Mougin, E.1; Grippa, M.1; Tucker, C. J.2
通讯作者Dardel, C.
来源期刊REMOTE SENSING OF ENVIRONMENT
ISSN0034-4257
EISSN1879-0704
出版年2014
卷号140页码:350-364
英文摘要

Desertification of the Sahel region has been debated for decades, while the concept of a "re-greening" Sahel appeared with satellite remote sensing data that allowed vegetation monitoring across wide regions and over increasingly long series of years (nowadays 30 years with the GIMMS-3g dataset). However, the scarcity of long-term field observations of vegetation in the Sahel prevents ground validation and deeper analysis of such trends. After assessing the consistency of the new GIMMS-3g NDVI product by comparison to three other AVHRR-NDVI datasets and MODIS NDVI, regional GIMMS-3g NDVI trends over 1981-2011 are analyzed. Trends are found positive and statistically significant almost everywhere in Sahel over the 1981-2011 period. Long-term field observations of the aboveground herbaceous layer mass have been collected within the Gourma region in Mali (1984-2011) and within the Fakara region in western Niger (1994-2011). These observations sample ecosystem and soil diversity, thus enabling estimation of averaged values representative of the Gourma and Fakara. NDVI measurements are found in good agreement with field observations, both over the Gourma and Fakara regions where re-greening and negative trends are observed respectively. A linear regression analysis performed between spatially averaged seasonal NDVI and a weighted average of field measurements explains 59% of the variability for the Gourma region over 1984-2011, and 38% for the Fakara region over 1994-2011. In the Gourma, which is a pastoral region, the re-greening trend is mainly observed over sandy soils, and attests for the ecosystem’s resilience to the 1980s’ drought, able to react to the more favorable rainfall of the 1990s and 2000s. However, contrasted changes in the landscape’s functioning have occurred locally. An increase in erosion and run-off processes in association with decreasing or stable vegetation cover was observed over shallow soils, which occupy 30% of the area. In the agro-pastoral Fakara, the decreasing trends observed both from satellite NDVI and field assessments of herbaceous mass are hardly explained by rainfall. These results give confidence in the dominant positive trends in Sahelian greenness, but indicate that degradation trends can also be observed, both in situ and from satellite time series. (C) 2013 Elsevier Inc. All rights reserved.


英文关键词Sahel Desertification Re-greening Trend analysis Herbaceous production NDVI AVHHR Field measurements Mali Niger
类型Article
语种英语
国家France ; USA
收录类别SCI-E
WOS记录号WOS:000329766200030
WOS关键词WEST-AFRICAN COLONIES ; AVHRR-NDVI DATA ; VEGETATION DYNAMICS ; HAPEX-SAHEL ; SEMIARID ENVIRONMENT ; SAHARA DESERT ; DATA SETS ; DESERTIFICATION ; MODIS ; TRENDS
WOS类目Environmental Sciences ; Remote Sensing ; Imaging Science & Photographic Technology
WOS研究方向Environmental Sciences & Ecology ; Remote Sensing ; Imaging Science & Photographic Technology
资源类型期刊论文
条目标识符http://119.78.100.177/qdio/handle/2XILL650/184708
作者单位1.Observ Midi Pyrenees, UMR CNRS UPS IRD CNES 5563, F-31400 Toulouse, France;
2.NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA
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Dardel, C.,Kergoat, L.,Hiernaux, P.,et al. Re-greening Sahel: 30 years of remote sensing data and field observations (Mali, Niger)[J],2014,140:350-364.
APA Dardel, C.,Kergoat, L.,Hiernaux, P.,Mougin, E.,Grippa, M.,&Tucker, C. J..(2014).Re-greening Sahel: 30 years of remote sensing data and field observations (Mali, Niger).REMOTE SENSING OF ENVIRONMENT,140,350-364.
MLA Dardel, C.,et al."Re-greening Sahel: 30 years of remote sensing data and field observations (Mali, Niger)".REMOTE SENSING OF ENVIRONMENT 140(2014):350-364.
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