@PhDThesis{Hirota:2010:EsMo,
author = "Hirota, Marina",
title = "Os efeitos de inc{\^e}ndios naturais e das mudan{\c{c}}as
clim{\'a}ticas globais na distribui{\c{c}}{\~a}o da
vegeta{\c{c}}{\~a}o na Am{\'e}rica do Sul tropical - um estudo
de modelagem",
school = "Instituto Nacional de Pesquisas Espaciais (INPE)",
year = "2010",
address = "S{\~a}o Jos{\'e} dos Campos",
month = "2010-09-03",
keywords = "mudan{\c{c}}as clim{\'a}ticas, modelagem conceitual,
transi{\c{c}}{\~a}o floresta-cerrado, fogo natural, biomas da
Am{\'e}rica do Sul, climate change, conceptual modeling,
forest-savanna boundary, natural fires, South American biomes.",
abstract = "Elaborou-se um modelo conceitual clima-vegeta{\c{c}}{\~a}o-fogo
natural (CVFN) para avaliar a sensibilidade e vulnerabilidade da
floresta, da savana e da transi{\c{c}}{\~a}o floresta-savana a
mudan{\c{c}}as ambientais globais, na Am{\'e}rica do Sul
tropical. Inicialmente, em condi{\c{c}}{\~o}es ambientais
atuais, os resultados do modelo CVFN sugeriram que na
aus{\^e}ncia de inc{\^e}ndios, as florestas tropicais se
estenderiam em aproximadamente 200 km para oeste sobre o
dom{\'{\i}}nio sav{\^a}nico atualmente observado.
Posteriormente, mudan{\c{c}}as ambientais na
precipita{\c{c}}{\~a}o, temperatura e descargas el{\'e}tricas
foram impostas ao modelo. Essas altera{\c{c}}{\~o}es, que em
forma agregada representam as mudan{\c{c}}as clim{\'a}ticas
esperadas devido ao aquecimento global e ao desmatamento, variam
entre um aquecimento de 2°C a 6°C, entre +10\% a -20\% de
precipita{\c{c}}{\~a}o, e O a 15\% de aumento no n{\'u}mero de
raios. As altera{\c{c}}{\~o}es mais cr{\'{\i}}ticas na
vegeta{\c{c}}{\~a}o foram projetadas para o extremo leste da
bacia Amaz{\^o}nica, com um alargamento da transi{\c{c}}{\~a}o
floresta-savana de 150 km para 300 km, com perdas da cobertura
arb{\'o}rea variando entre 20\% e 85\%. Isso significa que
\$\sim\$ 6\% das {\'a}reas atualmente cobertas por florestas
poderiam potencialmente se transformar em paisagens sav{\^a}nicas
abertas (dominadas por gram{\'{\i}}neas). O mecanismo que
controla essa redu{\c{c}}{\~a}o arb{\'o}rea consiste na
combina{\c{c}}{\~a}o de condi{\c{c}}{\~o}es clim{\'a}ticas
menos favor{\'a}veis para {\'a}rvores e mais atividade de fogo.
Adicionalmente, essa an{\'a}lise de sensibilidade previu que o
vegeta{\c{c}}{\~a}o de caatinga no Nordeste do Brasil poderia
potencialmente se tornar um solo descoberto. Por outro lado, a
sensibilidade clim{\'a}tica a mudan{\c{c}}as individuais e
concomitantes de cobertura da terra na Amaz{\^o}nia (AMZ), no
Cerrado (CER) e no Nordeste do Brasil (NEB) tamb{\'e}m foi
avaliada atrav{\'e}s de simula{\c{c}}{\~o}es utilizando o
MCGA/CPTEC. Os resultados do experimento de aridiza{\c{c}}{\~a}o
do CER n{\~a}o foram conclusivos. Ainda, al{\'e}m dos efeitos
locais da {"}savaniza{\c{c}}{\~a}o{"} da AMZ (SAV) e da
desertifica{\c{c}}{\~a}o do NEB (DES), os quais j{\'a} foram
estudados anteriormente e ratificados neste trabalho, dois novos
aspectos foram abordados para ambas {\'a}reas: a
avalia{\c{c}}{\~a}o de efeitos n{\~a}o-locais e
sin{\'e}rgicos. De acordo com os resultados, os impactos
n{\~a}o-locais s{\~a}o importantes para AMZ e NEB, e devem ser
inclu{\'{\i}}dos para futuras avalia{\c{c}}{\~o}es da
sensibilidade clim{\'a}tica. No contexto dos impactos
sin{\'e}rgicos, para a AMZ, o efeito l{\'{\i}}quido da
degrada{\c{c}}{\~a}o simult{\^a}nea SAV e DES (denominado SD)
na precipita{\c{c}}{\~a}o poderia ser aproximado pela soma
linear dos efeitos locais (SAV) e n{\~a}o-locais (DES). A
hip{\'o}tese de linearidade, no entanto, falha para o NEB: o
efeito l{\'{\i}}quido de SD foi menor que a soma linear das
anomalias locais (DES) e n{\~a}o-locais (SAV); processos de
sinergia agiram para compensar as anomalias de
precipita{\c{c}}{\~a}o, e o efeito l{\'{\i}}quido foi
pr{\'o}ximo ao resultado do experimento individual DES. ABSTRACT:
We used a climate-vegetation-natural fire conceptual model (CVNF)
to evaluate the sensitivity and vulnerability of forest, savanna,
and forest-savanna transition to environmental changes in tropical
South America. Initially, under current environmental conditions,
CVNF model results suggested that in the absence of fires,
tropical forests would extend westward about 200 km into the
presently-observed savanna domain. Then, environmental changes
were imposed upon the model in temperature, precipitation and
lightning strikes. These changes range from 2°C to 6°C warming,
+10\% to -20\% of precipitation changes and 0 to 15\% increase
in lightning frequency, which, in aggregate form, mimic the
expected future climatic changes in response to global warming and
deforestation. The most critical vegetation changes were projected
to take place over the easternmost portions of the basin, with a
widening of the forest-savanna transition. The transition width
would increase from 150 km to about 300 km, with tree cover losses
ranging from 20\% to 85\%. This means that \$\sim\$ 6\% of
the areas currently covered by forests could potentially turn into
grass-dominated savanna landscapes. The mechanism driving tree
cover reduction consists of a combination of less favorable
climate conditions for trees and more fire activity. In addition,
this sensitivity analysis predicted that the current dry shrubland
vegetation of NE Brazil could potentially turn into a bare soil
landscape. On the other hand, the climatic effects of individual
and concurrent (or combined) land-cover changes in Amazonia (AMZ),
Cerrado (CER) and Northeast Brazil (NEB) were also evaluated by
simulations using the CPTEC AGCM. The experiment of CER
aridization was not conclusive. Moreover, besides the local
effects of AMZ {"}savannization{"} (SAV) and NEB desertification
(DES), which have been studied previously and were ratified here,
we addressed two new aspects over both areas: the evaluation of
non-local and synergystic effects. According to our results,
non-local impacts are markedly important for both AMZ and NEB
regions and shoud be considered for future assessments on climatic
sensitivity. In the context of the synergystic impacts, for AMZ,
the net effect of concurrent SAV and DES (SD) on precipitation
could be approximated by a linear sum between the local (SAV) and
non-local effects (DES). This linear additivity assumption,
however, failed for NEB: the net effect (SD) was weaker than the
linear sum between the local (DES) and non-local effects (SAV);
synergistic processes acted to compensate the precipitation
anomalies, and the net effect was close to the individual DES
experiment.",
committee = "Orsini, Jos{\'e} Antonio Marengo (presidente) and Nobre, Carlos
Afonso (orientador) and Oyama, Marcos Daisuke (orientador) and
Pinto Junior, Osmar and Rocha, Humberto Ribeiro da and Pillar,
Val{\'e}rio De Patta",
copyholder = "SID/SCD",
englishtitle = "The role of natural fires and the impacts of global climate
changes on the vegetation distribution of tropical South America -
A modeling study",
language = "pt",
pages = "132",
ibi = "8JMKD3MGP7W/384KSSE",
url = "http://urlib.net/ibi/8JMKD3MGP7W/384KSSE",
urlaccessdate = "21 maio 2024"
}