Distribuição e intensidade de derrubadas de floresta causadas por vento na Amazônia em janeiro de 2005
A large number of blowdowns occurred in Amazonia in mid-January of 2005 when a squall line traversed 4.6 million km2 of forest, propagating from SW to NE. This paper describes the spatial distribution of blowdown forest damage and tree mortality across Amazonia attributed to that event, consideri...
| Autor principal: | Araujo, Raquel Fernandes de |
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| Grau: | Dissertação |
| Idioma: | por |
| Publicado em: |
Instituto Nacional de Pesquisas da Amazônia - INPA
2020
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| Acesso em linha: |
https://repositorio.inpa.gov.br/handle/1/5129 http://lattes.cnpq.br/2890034429403066 |
| Resumo: |
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A large number of blowdowns occurred in Amazonia in mid-January of 2005 when a squall
line traversed 4.6 million km2 of forest, propagating from SW to NE. This paper describes the
spatial distribution of blowdown forest damage and tree mortality across Amazonia attributed
to that event, considering disturbance patches > ~3 ha in size. In Landsat images, blowdowns
associated with the January 2005 squall line exhibit a distinct geometry. They are either
diffuse or have SW to NE directed lineaments. Thirty sample polygons were allocated across
the Amazon region, each containing 15,000 km2 of continuous forest. These were visually
inspected at 1:80,000 scale in Landsat TM RGB images (bands 5-4-3) from the 2005 dry
season. All blowdown footprints <~1y old and >~3 ha were recognized by spectral pattern
and geometry. After linear spectral unmixing with CLASLite, the disturbed pixels were
identified within each blowdown by a threshold of the pure vegetation fraction (≤85%) then
summed within each 15,000 km2 sample. The percent of forest damaged and attributed to this
single squall line was then interpolated between the 30 sample centroids. Based on field dates,
the mortality was estimate to the study area. As verified by field visits, diffuse blowdowns
observed on Landsat images were caused by January 2005 squall line. Damage was found to
be highly concentrated near Central Amazonia, not widespread. Nonetheless, blowdowns
attributed to this single squall line contributed over half of all annual blowdown area detected
in 30 samples across Amazonia for that year. The total number of dead trees in squall line
forest area was ~11 million trees. The major mortality occurred at Manaus region, with
~440,000 dead trees. Leaving a single Landsat scene out of the sample would cause a large
difference in the estimate of total damage. |