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Brazil

“Phenological shifts and variations in vegetation along Amazon eco-climatic transect using MODIS VI time series” P. Ratana, A. Huete, Y. Yin, and A. Jacobson and K. Didan Terrestrial Biophysics and Remote Sensing Lab ( TBRS ) Soil Water and Environmental Science Department

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Brazil

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  1. “Phenological shifts and variations in vegetation along Amazon eco-climatic transect using MODIS VI time series” P. Ratana, A. Huete, Y. Yin, and A. Jacobson and K. Didan Terrestrial Biophysics and Remote Sensing Lab (TBRS) Soil Water and Environmental Science Department University of Arizona 27 July 2004

  2. Rainforest Rainforest Cerrado Cerrado Brazil • Tropical rainforest and Brazilian savanna are the major land cover types in Brazil, covers nearly 6 million km². • Climate (i.e. rainfall pattern) is the major determinant, whilst topography and soils are subregion determinant for Amazonian rainforest, cerrado and their boundaries. • Recent issues, rapid deforestation and land conversion in rainforest and cerrado impacts biological diversity, the hydrological cycle, energy balance, climate and carbon dynamics at local and regional levels. • To better understand the consequences, improved knowledge of vegetation dynamics is needed.

  3. Purposes of Study • To analyze seasonal patterns of photosynthetic activity and spatio-temporal variability of vegetation along an Amazon eco-climatic transect using multitemporal MODIS Vegetation Indices (VI) products. • To investigate the discrimination of cerrado, transition zone and rainforest using MODIS VI temporal domain. • To investigate the temporal-seasonal characteristics of converted areas in forest, cerrado, and transition zone.

  4. Cerrado Amazonian forest • Rainforest covers Brazil nearly 4 million km2in Ar Köppen classification climate with average annual rainfall about 2150 mm/y • Until year 2000, more than 50 millions of hectares were deforested and converted to pasture. Annual rate of deforestation rages 15,000 – 30,000 km2 /y . • Cerrado covers approximately 2 million km2 of Brazil, falls in Aw Köppen classification climate with average annual rainfall 1500 mm/y. • Currently, the cerrado biome is suffering by human activities associated with conversion, high fire incidence, and invasive alien species. • It has been reported that the rate of cerrado conversion exceeds rainforest conversion. Forest-cerrado boundary • (1) the external limits or edges of a particular stand : vegetation type/composition or areas cleared by disturbance. • (2) transition zone or “ecotone”: previous studies found cerradão occurred between forest and savanna. • They also found, however, some areas had abrupt change between forest and cerrado due to climatic, geologic, and edaphic conditions.

  5. Rainfall quantity and seasonality • Brasilia has annual precipitation ~1500mm, 4-5 months dry season. • Porto Nacional has annual precipitation ~ 1650mm, higher precipitation in wet season than Brasilia. • Xingu has 4 months of dry season (May to August). • Dry season in Santarem starts August through October with annual rainfall ~2000mm. • From north to south, length of dry season increases steadily from 3 to 5 months.

  6. Terra Platform Data • Moderate Resolution Imaging Spectroradiometer (MODIS) 250m and Climate Modeling Grid (CMG), 0.05 degree, 16-day composite Vegetation Index (NDVI and EVI) products To isolate “green”, photosynthetic active signal and allow meaningful spatial and temporal interpretations of vegetation activity. Useful to monitor photosynthetic activity & study phenology. • 4-year MODIS VI data (Feb 2000 to Apr 2004) • 30-year average rainfall data from Global Historical Climatology Network (GHCN) • Landsat images acquired 07/2001

  7. South-to-North Transect: Cerrado-to-Rainforest • Delineated an eco-climatic transect onto MODIS VI images, then extracted CMG NDVI and EVI values (1 and 1x3 pixels) along the transect • Averaged VI values into one representative value for each 16-day composite, one month, and 4-year average • Generated temporal profiles Cerrado and Tropical rainforest biomes • Selected extraction sites for cerrado and rainforest biomes based on site visits and Ikonos and Landsat images • Then, extracted 250m VI values : 1, 3x3 and 7x7 pixels • Averaged into one representative value for each month • Generated temporal profiles

  8. Palmas Xingu Santarem Brasilia Amazon eco-climatic transect • Vegetation phenological responses and dynamics are related to seasonal dynamics. • At a given time period, the “greenness” changes along the eco-climatic transect, the further north the higher VI values. • Vise versa, for the same geographic location, VI values change due to seasonal vegetation responses.

  9. Interannual Variations Iriri Xingu Tocantins Araguaia • From 4-year July composites of NDVI and EVI along the eco-climatic transect, there are year-to-year variations, results from climatic variability and may be from vegetation composition. • However, same trend could be found in the profiles, lower VI values in the south, Brasilia-Palmas, and higher in the north, Xingu-Santarem, of the transect.

  10. Seasonal Response Palmas Xingu Santarem Brasilia • We found a sloped , “boundary”, between north (forest) and south (cerrado) around lat-8.05S long-50.45W to lat-7.55S long-50.95W

  11. Cerrado and Rainforest Cerrado Rainforest

  12. Periodic biological events or “phenology” in vegetations are driven by climate. • The complex species-, seasonal-, annual-, local-, and regional-specific phenological response to changes in rainfall. • Transition zone VI seasonal profiles fall in between cerrado and rainforest seasonal profile.

  13. Converted pasture Cerrado and their conversion Brasilia Nation Park Rio de Janeiro Farm

  14. Forests and their conversion Santarem Km67 Santarem Pasture

  15. Conclusions • Complex spatio-temporal variations were caused by climate, vegetation composition, and landscape at the regional scale. • From temporal profiles of the transect, both NDVI and EVI showed unique patterns for cerrado, rainforest and transition zone. • The 4-year average seasonal profiles along the eco-climatic transect depicted nicely the cerrado, rainforest, and the transition zone. • Due to their differences in phenological phenomena, converted cerrado and forest conversion can be detected and monitored with the MODIS sensor. • MODIS, broad areal coverage and fine temporal resolution, posses significant potential for phenology and vegetation dynamics study over the Amazon eco-climatic region. • However, a better correlation of conventional phenology with remotely sensed greenness measures is needed for maximum effectiveness.

  16. Acknowledgement Thank you • This work was supported by NASA LBA grant NCC-5603 and MODIS contract NAS5-31364.

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