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LC-19 Abstract

Use of Airborne Remote Sensing for Uncertainty Assessments in Regional Extrapolations of Ground LBA Ecology Measurements with MODIS Data

Laerte Ferreira — UFG - LAPIG (SA-PI)
Alfredo R. Huete — University of Arizona (US-PI)
Edson Eyji Sano — EMBRAPA (SA-PI)


The Cerrado and Amazon Forest Cerrado transition are the most intensely

stressed areas in Brazil, with rapid and aggressive land use conversions. 

This study aims to scale-up and extrapolate ground-measured ecological

parameters, such as fraction of absorbed photosynthetically-active radiation (fAPAR)

and leaf area index (LAI), over this fragmented and heterogeneous region in

Brazil.  Synoptic and repetitive fAPAR and LAI estimations are crucial as

inputs in regional-scale productivity and carbon budget models, prompting many

remote sensing investigations for the development of techniques for

satellite-based LAI/fAPAR retrievals.


We propose low level AVIRIS flights for scaling-up field measured, ecologic

parameters (fAPAR, LAI, %cover) across an environmental gradient spanning the

diverse Brazilian cerrado biome (dry grassland woodland cerrado cerrado-forest

transition) to the seasonal Amazon forest biome, including their land use and

land converted classes.   As part of the scaling-up process, we will

use AVIRIS hyperspectral reflectances to identify and discriminate the natural

and altered land cover classes along the gradient of vegetation types using

mixture models based on 'pure spectral signatures' of 'endmember' grassland,

woodland, forest classes. This refined land cover characterization will be used

in the scaling up of fAPAR, LAI, and % cover to AVIRIS pixel size (5 m) and the

coarser Landsat ETM+ (30 m) and MODIS (250 m to 1 km) sensors. Our scaling and

extrapolation approach will result in regional mapped products, with an accuracy

and uncertainty fields, that account for distinct, land cover dependent,

functional relationships between ecologic parameter (linear and non-linear) and

vegetation indices. The scaled-up regional products will account for

inter-sensor translation and continuity and will provide an independent

'validation' of the LAI/fPAR, land cover, and surface reflectance/VI MODIS

products (both Terra and Aqua) for the cerrado,  transition, and forest

study areas.  The results of this study will enable the detection of

'hotspots' of land conversion activities with the MODIS sensor;  enable for

their fine-scale analysis with the Landsat ETM+ sensor or ASTER sensor; and

allow a time-series analysis with the AVHRR historical data. This will greatly

aid seasonal and inter-annual carbon balance studies in the Cerrado and Amazon

transition regions.

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