aag 2010 washington dc assessing savanna ecosystem changes with remote sensing in east africa jiaguo...
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AAG 2010 Washington DC
Assessing Savanna Ecosystem Changes with
Remote Sensing in East Africa
Jiaguo Qi1,Chuan Qin1 , Gopal Alagarswamy1, Joseph Ogutu2,
Mohamed Said2, Simon Mugatha2, Simon Mwansasu3, Pauline Noah3, Joseph Maitima2, Pius Z. Yanda3
1. Michigan State University; 2. International Livestock Research Institute, Nairobi, Kenya; 3. University of Dar Es Salaam
AAG 2010 Washington DC
RATIONALE
• Savannah system in E.A. is sensitive to disturbances– Climate change
• Drought and flood• Pattern shifting
– Human• Change in grazing intensity,
fires, conversion
Climate Change
Land Management
Savanna Vegetation
Livelihood Systems
AAG 2010 Washington DC
OBJECTIVE
• To assess phenological changes of savannah system in East Africa using remote sensing– Phenology is an important attribute as it
• Reflects ecosystem dynamics• Shifts with changes in climate patterns• Changes with land use
– Spatio-temporal pattern of phenology can have significant implications for human and climate systems
AAG 2010 Washington DC
DATA
• Long term record (1982-2006) of remote sensing data– GIMMS (Global Inventory Modeling and Mapping Studies)
NDVI (Normalized Difference Vegetation Index) data (Tucker, 2004 )
• Rainfall Data– CRU data
• Land Cover– UMD Global Land Cover Classification (Hansen, 1998)
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METHODS
• Extract phenological attributes
• A linear/simple regression to examine the trends;
• Quantify spatial patterns• Analyze the rainfall data to
examine the relationship between climate and vegetation change
Jönsson and Eklundh, 2002; Jönsson and Eklundh, 2004
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RESULTS• Large Integral - Productivity
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“Large Integral” Change (1982-2006)
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“Large Integral” Change (1982-2006)
Finer resolution analyses:
1. Northern site in Kenya
2. Tarangire Park and surroundings in Tanzania
1
2
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Northern Kenya Site
1
AAG 2010 Washington DC
Northern Kenya Site• Land Cover type
– Grassland/Shrubland
• Phenology : Bi-modal season– 1st season
• Start: March – April• End: June – July
– 2nd season• Start: October-November• End: January - February
1982 1983
2005 2006
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Northern Kenya Site
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Tarangire Park in Tanzania
Tarangire Park
Outside the park
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Tarangire Park in Tanzania
• Land Cover type– Wooded Grassland
• Phenology : – Single-season
• Start: November-December• End: May - June
1982 1983
2005 2006
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Tarangire Park in Tanzania
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Tarangire Park in Tanzania
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SUMMARY
• Phenological Changes– Some places are bi-modal while others are
uni-modal– May be a false alarm - Places of bi-modal
seasons may show uni-modal in drought years Change may not be long term
– There is a shift from bi-modal towards unimodal in some places
– It appears that climate is a dominant driver in Tanzania study site
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CONCLUSIONS
• Phenology is an important indicator of ecosystems
• Can be characterized with remotely sensed data• Shifts in spatial patterns of phenology are either
an indicator of climate change or human land use changes, or combination of the two
• There is a need to separate the two, which will be the work in the future
AAG 2010 Washington DC
Questions?