Termotolerância foliar em espécies de formações savânicas e florestais
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Data
2021-06-01
Autores
da Silva, Bianca Helena Porfírio [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O aumento da temperatura causado pelas recentes mudanças climáticas vem afetando a estrutura e o funcionamento de ecossistemas tropicais segundo dados do IPCC. O aumento da temperatura média dos trópicos demonstra que plantas desses sistemas serão expostas a temperaturas acima da faixa ótima para certas funções fisiológicas, especialmente as taxas fotossintéticas, acarretando assim danos às espécies que não possuem características que confiram termotolerância. O Cerrado é um ecossistema tropical savânico extremamente diverso, que tem passado por dinâmicas sucessionais, como a invasão de espécies típicas de formações florestais, que são favorecidas na ausência de episódios de fogo. Em áreas no interior do estado de São Paulo frequentemente encontramos transições entre formações florestais da Mata Atlântica (floresta estacional semidecidual) e de Cerrado (cerradão) dividindo a paisagem com formações savânicas. Diante do novo cenário ambiental de aquecimento global e levando em consideração as projeções futuras, espécies florestais podem estar sendo desfavorecidas pelo aumento da temperatura, já que em períodos quentes e secos espécies florestais não são capazes de avançar sobre sobre áreas savânicas. O presente estudo objetivou comparar a termotolerância de espécies arbóreas do cerrado típico e de duas formações florestais (cerradão e floresta estacional semidecidual) expostas à altas temperaturas e quais aspectos morfológicos e fenológicos (perenes x decíduas) dessas espécies poderiam estar relacionados a termotolerância, testando se espécies típicas de savanas seriam mais termotolerantes que as espécies presentes em formações florestais, o que ajudaria a conter a expansão florestal dentro de ambientes savânicos. Os resultados obtidos evidenciaram que espécies de formações de cerrado típico e de cerradão não diferem na sua capacidade de termotolerância (49,80±0,49°C e 49,71±0,71°C, respectivamente), porém o hábito foliar está fortemente relacionado a capacidade de tolerar altas temperaturas. Espécies perenes, independentemente de sua origem (cerrado típico x cerradão), se mostraram mais termotolerantes que as espécies decíduas. As espécies tropicais de floresta estacional apresentaram a mesma termotolerância que espécies de cerrado típico (47,78±0,51°C e 49,36±0,59°C, respectivamente), indicando que somente a temperatura não afetará as dinâmicas de fronteira desses dois ecossistemas. Os resultados obtidos neste estudo fornecem informações importantes sobre a ecofisiologia de espécies do sistema savânico e florestais frente às elevações na temperatura média global impostas pelo aquecimento global.
According to the IPCC data, temperature increases due to climatic changes are affecting the structure and functioning of tropical ecosystems. Increases in the average temperature of the tropics demonstrates that the plants in these systems will be exposed to temperatures above the optimum range for certain physiological functions, such as photosynthetic rates, leading to significant decrease of species performance, especially in those lacking traits that confirm thermotolerance. The Cerrado is a diverse tropical ecosystem, where savanna vegetation have been subjected to the invasion of typical forest species of adjacent vegetation. In transitional areas, such as those of São Paulo state, it is possible to find forest vegetation of the Atlantic Forest (semideciduous seasonal forest) and Cerrado (cerradão) side by side in the landscape with typical open savannas (typical cerrado). In view of the scenario of global warming, and taking into account the IPCC future projections, forest species may be disadvantaged by the increase in temperature, since in hot and dry periods forest species are not able to advance over savanna areas. The present study aimed to compare leaf thermotolerance of tree species from typical cerrado and from two forest formations (cerradão and semideciduous seasonal forest) exposed to high temperatures, testing whether the typical savanna species were more thermotolerant than those species present in forest formations. Additionally, we tested which aspect are more related to thermotolerance, plant origin or phenology The results showed that typical cerrado and cerradão species do not differ in their thermotolerance capacity (49,80±0,49°C e 49,71±0,71°C, respectively), however the leaf habit (evergreen x deciduous) is strongly related to the ability to tolerate high temperatures. Perennial species regardless of their origin (typical cerrado x cerradão) are more thermotolerant than deciduous species. The tree species of semideciduous forest have similar leaf thermotolerance as the typical savanna species (47,78±0,51°C e 49,36±0,59°C, respectively), suggesting that temperature alone will not affect the frontier dynamics of these two ecosystems. The results obtained in this study provide important information about the ecophysiology of species in the Cerrado and forest systems in view of the increases in the average global temperature imposed by global warming.
According to the IPCC data, temperature increases due to climatic changes are affecting the structure and functioning of tropical ecosystems. Increases in the average temperature of the tropics demonstrates that the plants in these systems will be exposed to temperatures above the optimum range for certain physiological functions, such as photosynthetic rates, leading to significant decrease of species performance, especially in those lacking traits that confirm thermotolerance. The Cerrado is a diverse tropical ecosystem, where savanna vegetation have been subjected to the invasion of typical forest species of adjacent vegetation. In transitional areas, such as those of São Paulo state, it is possible to find forest vegetation of the Atlantic Forest (semideciduous seasonal forest) and Cerrado (cerradão) side by side in the landscape with typical open savannas (typical cerrado). In view of the scenario of global warming, and taking into account the IPCC future projections, forest species may be disadvantaged by the increase in temperature, since in hot and dry periods forest species are not able to advance over savanna areas. The present study aimed to compare leaf thermotolerance of tree species from typical cerrado and from two forest formations (cerradão and semideciduous seasonal forest) exposed to high temperatures, testing whether the typical savanna species were more thermotolerant than those species present in forest formations. Additionally, we tested which aspect are more related to thermotolerance, plant origin or phenology The results showed that typical cerrado and cerradão species do not differ in their thermotolerance capacity (49,80±0,49°C e 49,71±0,71°C, respectively), however the leaf habit (evergreen x deciduous) is strongly related to the ability to tolerate high temperatures. Perennial species regardless of their origin (typical cerrado x cerradão) are more thermotolerant than deciduous species. The tree species of semideciduous forest have similar leaf thermotolerance as the typical savanna species (47,78±0,51°C e 49,36±0,59°C, respectively), suggesting that temperature alone will not affect the frontier dynamics of these two ecosystems. The results obtained in this study provide important information about the ecophysiology of species in the Cerrado and forest systems in view of the increases in the average global temperature imposed by global warming.
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Palavras-chave
Cerrado, Floresta tropical, Ecofisiologia vegetal, Aquecimento global, Ecologia dos cerrados, Climate change, Gglobal warming, Savanna, Tropical forest, Plant ecology, Plant physiology, Hábito foliar, Savanas, Termotolerância, Leaf habit, Cerradão, Thermotolerance