Analysis of cerrado physiognomies and conversion in the modis seasonal-temporal domain
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Data
2005
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Resumo
The “cerrado” biome in central Brazil is rapidly being converted
into pasture and agricultural crops with important consequences for local
and regional climate change and regional carbon fluxes between the atmosphere
and land surface. Satellite remote sensing provides an opportunity to
monitor the highly diverse and complex cerrado biome, encompassing grassland,
shrubland, woodland and gallery forests, and converted areas. In this
study, the potential of Terra Moderate Resolution Imaging Spectroradiometer
(MODIS) data is analyzed to discriminate among these diverse cerrado physiognomies
and converted pastures based on their seasonal dynamics and phenology.
Four years (2000–03) of MODIS 16-day composited, 250-m resolution
vegetation index (VI) data were extracted over a series of biophysically
sampled field study sites representing the major cerrado types. The temporal VI
profiles over the cerrado formations exhibited high seasonal contrasts with a
pronounced dry season from June to August and a wet growing season from November to March. The converted pasture areas showed the highest seasonal
contrasts while the gallery forest formation had the lowest contrast. Seasonal
VI variations were negatively correlated with woody canopy crown cover and
provided a method to discriminate among converted cerrado areas, gallery
forests, and the woody and herbaceous cerrado formations. The grassland and
shrub cerrado formations, however, were difficult to separate based on their
seasonal VI profiles. Maximum discrimination among the cerrado types occurred
during the dry season where a positive linear relationship was found
between VI and green cover. The annual integrated VI values showed the
gallery forests and cerrado woodland as having the highest, and hence most
annual productivity, while the more herbaceous shrub and grassland cerrado
types were least productive. The cumulative VI profiles of converted cerrado,
pasture areas varied distinctly in shape due to their strong dry season inactivity.
Furthermore, the annual integrated VI values of the converted pastures differed
significantly between the normalized difference vegetation index (NDVI) and
the enhanced vegetation index (EVI) MODIS VI products, resulting in large
discrepancies in productivity estimates relative to the native cerrado sites. This
study shows that the MODIS seasonal–temporal VI profiles are highly useful
in monitoring the cerrado biome and conversion-related activities.
Descrição
Palavras-chave
Cerrado, Temporal domain, MODIS, Phenology, Remote sensing
Citação
RATANA, P.; HUETE, A. R.; FERREIRA, L. Analysis of cerrado physiognomies and conversion in the modis seasonal-temporal domain. Earth Interactions, New York, v. 9, n. 3, p. 1-22, 2005.