Ground-and satellite-based evidence of the biophysical mechanisms behind the greening Sahel
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Ground-and satellite-based evidence of the biophysical mechanisms behind the greening Sahel. / Brandt, Martin Stefan; Mbow, Cheikh; Diouf, Abdoul A.; Verger, Aleixandre; Samimi, Cyrus; Fensholt, Rasmus.
I: Global Change Biology, Bind 21, Nr. 4, 01.04.2015, s. 1610-1620.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
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T1 - Ground-and satellite-based evidence of the biophysical mechanisms behind the greening Sahel
AU - Brandt, Martin Stefan
AU - Mbow, Cheikh
AU - Diouf, Abdoul A.
AU - Verger, Aleixandre
AU - Samimi, Cyrus
AU - Fensholt, Rasmus
PY - 2015/4/1
Y1 - 2015/4/1
N2 - After a dry period with prolonged droughts in the 1970s and 1980s, recent scientific outcome suggests that the decades of abnormally dry conditions in the Sahel have been reversed by positive anomalies in rainfall. Various remote sensing studies observed a positive trend in vegetation greenness over the last decades which is known as the re-greening of the Sahel. However, little investment has been made in including long-term ground-based data collections to evaluate and better understand the biophysical mechanisms behind these findings. Thus, deductions on a possible increment in biomass remain speculative. Our aim is to bridge these gaps and give specifics on the biophysical background factors of the re-greening Sahel. Therefore, a trend analysis was applied on long time series (1987-2013) of satellite-based vegetation and rainfall data, as well as on ground-observations of leaf biomass of woody species, herb biomass, and woody species abundance in different ecosystems located in the Sahel zone of Senegal. We found that the positive trend observed in satellite vegetation time series (+36%) is caused by an increment of in situ measured biomass (+34%), which is highly controlled by precipitation (+40%). Whereas herb biomass shows large inter-annual fluctuations rather than a clear trend, leaf biomass of woody species has doubled within 27 years (+103%). This increase in woody biomass did not reflect on biodiversity with 11 of 16 woody species declining in abundance over the period. We conclude that the observed greening in the Senegalese Sahel is primarily related to an increasing tree cover that caused satellite-driven vegetation indices to increase with rainfall reversal. Copyright
AB - After a dry period with prolonged droughts in the 1970s and 1980s, recent scientific outcome suggests that the decades of abnormally dry conditions in the Sahel have been reversed by positive anomalies in rainfall. Various remote sensing studies observed a positive trend in vegetation greenness over the last decades which is known as the re-greening of the Sahel. However, little investment has been made in including long-term ground-based data collections to evaluate and better understand the biophysical mechanisms behind these findings. Thus, deductions on a possible increment in biomass remain speculative. Our aim is to bridge these gaps and give specifics on the biophysical background factors of the re-greening Sahel. Therefore, a trend analysis was applied on long time series (1987-2013) of satellite-based vegetation and rainfall data, as well as on ground-observations of leaf biomass of woody species, herb biomass, and woody species abundance in different ecosystems located in the Sahel zone of Senegal. We found that the positive trend observed in satellite vegetation time series (+36%) is caused by an increment of in situ measured biomass (+34%), which is highly controlled by precipitation (+40%). Whereas herb biomass shows large inter-annual fluctuations rather than a clear trend, leaf biomass of woody species has doubled within 27 years (+103%). This increase in woody biomass did not reflect on biodiversity with 11 of 16 woody species declining in abundance over the period. We conclude that the observed greening in the Senegalese Sahel is primarily related to an increasing tree cover that caused satellite-driven vegetation indices to increase with rainfall reversal. Copyright
KW - Biodiversity
KW - Biomass monitoring
KW - Degradation
KW - Greening
KW - Sahel
KW - Vegetation change
UR - http://www.scopus.com/inward/record.url?scp=84924630351&partnerID=8YFLogxK
U2 - 10.1111/gcb.12807
DO - 10.1111/gcb.12807
M3 - Journal article
C2 - 25400243
AN - SCOPUS:84924630351
VL - 21
SP - 1610
EP - 1620
JO - Global Change Biology
JF - Global Change Biology
SN - 1354-1013
IS - 4
ER -
ID: 138394233