land degradation; greening; drought; Sahel; FAPAR time series; GIMMS3g; Geoland; biomass observations; Senegal; Mali
Abstract :
[en] Local vegetation trends in the Sahel of Mali and Senegal from Geoland Version 1
(GEOV1) (5 km) and the third generation Global Inventory Modeling and Mapping Studies
(GIMMS3g) (8 km) Fraction of Absorbed Photosynthetically Active Radiation (FAPAR)
time series are studied over 29 years. For validation and interpretation of observed greenness
trends, two methods are applied: (1) a qualitative approach using in-depth knowledge of
the study areas and (2) a quantitative approach by time series of biomass observations and
rainfall data. Significant greening trends from 1982 to 2010 are consistently observed in both
GEOV1 and GIMMS3g FAPAR datasets. Annual rainfall increased significantly during the
observed time period, explaining large parts of FAPAR variations at a regional scale. Locally,
GEOV1 data reveals a heterogeneous pattern of vegetation change, which is confirmed by
long-term ground data and site visits. The spatial variability in the observed vegetation trends
in the Sahel area are mainly caused by varying tree- and land-cover, which are controlled by
human impact, soil and drought resilience. A large proportion of the positive trends are
caused by the increment in leaf biomass of woody species that has almost doubled since the
1980s due to a tree cover regeneration after a dry-period. This confirms the re-greening of the Sahel, however, degradation is also present and sometimes obscured by greening. GEOV1
as compared to GIMMS3g made it possible to better characterize the spatial pattern of trends
and identify the degraded areas in the study region.
Disciplines :
Environmental sciences & ecology
Author, co-author :
Brandt, Martin
Verger, Aleixandre
Diouf, Abdoul Aziz ; Université de Liège - ULiège > Doct. sc. (sc. & gest. env. - Bologne)
Baret, Frédéric
Samimi, Cyrus
Language :
English
Title :
Local Vegetation Trends in the Sahel of Mali and Senegal Using Long Time Series FAPAR Satellite Products and Field Measurement (1982–2010)
Publication date :
2014
Journal title :
Remote Sensing
eISSN :
2072-4292
Publisher :
Multidisciplinary Digital Publishing Institute (MDPI), Basel, Switzerland
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