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Sampaio, Gilvan ^[1] ; Shimizu, Marilia H. ^[1] ; Guimaraes-Junior, Carlos A. ^[1] ; Alexandre, Felipe ^[1] ; Guatura, Marcelo ^[1] ; Cardoso, Manoel ^[1] ; Domingues, Tomas F. ^[2] ; Rammig, Anja ^[3] ; von Randow, Celso ^[1] ; Rezende, Luiz F. C. ^[1] ; Lapola, David M. ^[4]

Afiliação do(s) autor(es)

^[1] Inst Nacl Pesquisas Espaciais, Coordenacao Geral Ciencias Terra, BR-12227010 Sao Jose Dos Campos, SP - Brazil

^[2] Univ Sao Paulo, Dept Biol, BR-14040901 Ribeirao Preto, SP - Brazil

^[3] Tech Univ Munich, Land Surface Atmosphere Interact, D-85354 Freising Weihenstephan - Germany

^[4] Univ Estadual Campinas, Ctr Pesquisas Meteorol & Climat Aplicadas Agr, BR-13083886 Campinas, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: BIOGEOSCIENCES; v. 18, n. 8, p. 2511-2525, APR 22 2021.
• Citações Web of Science: 0

Resumo

The climate in the Amazon region is particularly sensitive to surface processes and properties such as heat fluxes and vegetation coverage. Rainfall is a key expression of the land surface-atmosphere interactions in the region due to its strong dependence on forest transpiration. While a large number of past studies have shown the impacts of large-scale deforestation on annual rainfall, studies on the isolated effects of elevated atmospheric CO2 concentrations (eCO(2)) on canopy transpiration and rainfall are scarcer. Here, for the first time, we systematically compare the plant physiological effects of eCO(2) and deforestation on Amazon rainfall. We use the CPTEC Brazilian Atmospheric Model (BAM) with dynamic vegetation under a 1.5 x CO2 experiment and a 100 % substitution of the forest by pasture grasslands, with all other conditions held similar between the two scenarios. We find that both scenarios result in equivalent average annual rainfall reductions (Physiology: -257 mm, -12 %; Deforestation: -183 mm, -9 %) that are above the observed Amazon rainfall interannual variability of 5 %. The rainfall decreases predicted in the two scenarios are linked to a reduction of approximately 20 % in canopy transpiration but for different reasons: the eCO(2)-driven reduction of stomatal conductance drives the change in the Physiology experiment, and the smaller leaf area index of pasturelands (-72 % compared to tropical forest) causes the result in the Deforestation experiment. The Walker circulation is modified in the two scenarios: in Physiology due to a humidity-enriched free troposphere with decreased deep convection due to the heightening of a drier and warmer (+2.1 degrees C) boundary layer, and in Deforestation due to enhanced convection over the Andes and a subsidence branch over the eastern Amazon without considerable changes in temperature (-0.2 degrees C in 2 m air temperature and +0.4 degrees C in surface temperature). But again, these changes occur through different mechanisms: strengthened west winds from the Pacific and reduced easterlies entering the basin affect the Physiology experiment, and strongly increased easterlies influence the result of the Deforestation experiment. Although our results for the Deforestation scenario agree with the results of previous observational and modelling studies, the lack of direct field-based ecosystem-level experimental evidence regarding the effect of eCO(2) on moisture fluxes in tropical forests confers a considerable level of uncertainty to any projections of the physiological effect of eCO(2) on Amazon rainfall. Furthermore, our results highlight the responsibilities of both Amazonian and non-Amazonian countries to mitigate potential future climatic change and its impacts in the region, driven either by local deforestation or global CO2 emissions. (AU)

• Processo FAPESP: 15/02537-7 - AmazonFACE/ME: projeto de integração Modelagem-Experimento do Amazon-FACE - o papel da biodiversidade e feedbacks climáticos
• Beneficiário: David Montenegro Lapola
• Modalidade de apoio: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Jovens Pesquisadores
• Processo FAPESP: 15/50687-8 - Serviços climáticos através de co-produção de conhecimento: uma iniciativa europeia e da América do Sul para fortalecer as ações de adaptação da sociedade a eventos extremos
• Beneficiário: Iracema Fonseca de Albuquerque Cavalcanti
• Modalidade de apoio: Auxílio à Pesquisa - Temático
• Processo FAPESP: 17/03048-5 - Simulações de distúrbios florestais e mudança de uso da terra na Amazônia e possíveis impactos no clima regional e chuvas no sudeste da América do Sul
• Beneficiário: Luiz Felipe Campos de Rezende
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 17/07135-0 - Avaliação do feedback da elevação de CO2 biosfera-atmosfera em clima regional
• Beneficiário: Carlos Augusto Guimarães Junior
• Modalidade de apoio: Bolsas no Brasil - Programa Capacitação - Treinamento Técnico
• Processo FAPESP: 15/50122-0 - Fenômenos dinâmicos em redes complexas: fundamentos e aplicações
• Beneficiário: Elbert Einstein Nehrer Macau
• Modalidade de apoio: Auxílio à Pesquisa - Temático