Respostas ecofisiológicas de plantas arbóreas do cerrado à geada
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Data
2019-03-25
Autores
Antonio, Ariadne Cristina De
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Universidade Estadual Paulista (Unesp)
Resumo
O Cerrado pode estar exposto a diversos distúrbios naturais moduladores, entre eles a geada. Este é um fenômeno capaz de afetar a distribuição e seleção de características de tolerância e sobrevivência das espécies nestas vegetações. Deste modo, o presente estudo pretendeu compreender os efeitos causados pela geada em espécies afetadas e não afetadas por este fenômeno, assim como quantificar características morfo-fisiológicas que possam explicar as respostas de rebrota a baixas temperaturas. As pesquisas foram realizadas em três locais distintos: em Águas de Santa Bárbara - SP na Estação Ecológica de Águas de Santa Bárbara – EecSB (acometida em 2016 por seis episódios de geada entre os meses de junho e agosto) (Capítulo I); Assis - SP na Estação Ecológica de Assis –EEA que foi acometida por eventos de geada no mesmo ano (Capítulo I e II) e na Reserva Ecológica do IBGE em Brasília – DF (Capítulo III). No segundo capítulo as coletas e experimentos foram realizados na EEA e no câmpus da Unesp. No capítulo I e II foram avaliados indivíduos de espécies previamente selecionadas após a ocorrência da geada, com o intuito de analisar os efeitos da mesma na mortalidade de indivíduos e ramos de espécies arbóreas consideradas como afetadas pelo fenômeno; também foi verificado se o espécime teve rebrote a partir do solo ou do caule/ramos e o grau de proteção das gemas, além disso, realizamos análises de respostas morfo-fisiológicas por meio da avaliação de atributos foliares, como, espessura da folha; área foliar; dimensões foliares; área foliar específica e respostas fotossintéticas (razão Fv:Fm). No capítulo III analisamos se os atributos relacionados a proteção ao fogo são importantes para proteger ramos das espécies lenhosas do cerrado contra as baixas temperaturas: quantificamos a posição das gemas e analisamos se a espessura e a densidade da casca atuam como isolantes térmicos. No capítulo I encontramos que as posições das gemas diferiram entre as espécies afetadas e não afetadas, e as espécies afetadas apresentaram diferentes respostas de rebrota de seus ramos. No capítulo II os parâmetros morfológicos não demonstraram grande influência sobre as divisões das espécies entre afetadas e não afetadas, sendo as respostas fotossintéticas a baixas temperaturas o fator que separou os grupos que haviam sido previamente determinados. As espécies afetadas e não afetadas responderam ao tratamento a baixas temperaturas como o esperado, sendo que as espécies afetadas apresentaram grandes declínios nos valores de Fv:Fm a baixas temperaturas. No capítulo III não foram encontradas diferenças na espessura da camada de casca interna e espécies com casca mais densa apresentaram maior variação de temperatura, porém a variação de temperatura foi positivamente relacionada com a densidade da casca. Conclui-se então que existem diferenças morfológicas e fisiológicas entre espécies afetadas e não afetadas, mostrando que a geada pode afetar aspectos da vegetação de cerrado podendo atuar em conjunto com outros moduladores da fisionomia savânica.
The Cerrado can be exposed to several natural disturbances, being frost one of them. Frost is a phenomenon that can affect the distribution and selects tolerance and survival characteristics of species occurring in these vegetations. This study aimed to understand the effects caused by frost on the biomass of frost affected and non-affected tree species, and to quantify morpho-physiological characteristics that may explain the regrowth responses after the exposition to low temperatures. Data collection was carried out in three different locations: the first chapter was developed in Águas de Santa Bárbara- SP at the Ecological Station of Águas de Santa Bárbara – EecSB, which was affected in 2016 by six episodes of frost between the months of June and August; data for first and second chapter were collected in Assis – SP at the Ecological Station of Assis –EEA, which was also affected by frost events in the same year. The chapter III was conducted at the IBGE Ecological Reserve in Brasília – DF. In the chapter II the collections and experiments were carried out in Assis in the EEA and in Unesp campus. In chapter I and II, individuals from preselected species were evaluated to analyze the effects of frost on the branch mortality of tree species considered to be affected by the phenomenon; additionally it was verified whether the specimen had regrowth from the soil or the stem / branches and the degree of protection of the buds. We performed analyzes of morpho-physiological responses through the evaluation of leaf attributes, such as leaf thickness; leaf area; leaf dimensions; specific leaf area and photosynthetic responses (Fv:Fm). In chapter III, we analyzed whether the attributes related to fire protection are important to protect branches of the woody species of the cerrado against temperature variations. We quantify the position of the buds and analyze if the thickness and the density of the bark act as thermal insulation. In the first chapter we found that the bud position differed between the two functional groups and the affected species showed different regrowth responses. In chapter II, the morphological parameters did not show great influence on the separation of the species between affected and non-affected, being the photosynthetic responses at low temperatures the most important factor separating the groups. The affected and non-affected species responded to the treatment at low temperatures as expected, and the affected species showed large declines in the Fv: Fm values under lower temperatures. In chapter III, the temperature variation was positively related to the bark density, but no differences were found in the inner bark thickness, and species with more density bark presented higher temperature variation. We concluded that there are morphological and physiological differences between affected and non-affected species showing that frost can affect aspects of Cerrado vegetation acting in conjunction with other modulators of the savanna physiognomy.
The Cerrado can be exposed to several natural disturbances, being frost one of them. Frost is a phenomenon that can affect the distribution and selects tolerance and survival characteristics of species occurring in these vegetations. This study aimed to understand the effects caused by frost on the biomass of frost affected and non-affected tree species, and to quantify morpho-physiological characteristics that may explain the regrowth responses after the exposition to low temperatures. Data collection was carried out in three different locations: the first chapter was developed in Águas de Santa Bárbara- SP at the Ecological Station of Águas de Santa Bárbara – EecSB, which was affected in 2016 by six episodes of frost between the months of June and August; data for first and second chapter were collected in Assis – SP at the Ecological Station of Assis –EEA, which was also affected by frost events in the same year. The chapter III was conducted at the IBGE Ecological Reserve in Brasília – DF. In the chapter II the collections and experiments were carried out in Assis in the EEA and in Unesp campus. In chapter I and II, individuals from preselected species were evaluated to analyze the effects of frost on the branch mortality of tree species considered to be affected by the phenomenon; additionally it was verified whether the specimen had regrowth from the soil or the stem / branches and the degree of protection of the buds. We performed analyzes of morpho-physiological responses through the evaluation of leaf attributes, such as leaf thickness; leaf area; leaf dimensions; specific leaf area and photosynthetic responses (Fv:Fm). In chapter III, we analyzed whether the attributes related to fire protection are important to protect branches of the woody species of the cerrado against temperature variations. We quantify the position of the buds and analyze if the thickness and the density of the bark act as thermal insulation. In the first chapter we found that the bud position differed between the two functional groups and the affected species showed different regrowth responses. In chapter II, the morphological parameters did not show great influence on the separation of the species between affected and non-affected, being the photosynthetic responses at low temperatures the most important factor separating the groups. The affected and non-affected species responded to the treatment at low temperatures as expected, and the affected species showed large declines in the Fv: Fm values under lower temperatures. In chapter III, the temperature variation was positively related to the bark density, but no differences were found in the inner bark thickness, and species with more density bark presented higher temperature variation. We concluded that there are morphological and physiological differences between affected and non-affected species showing that frost can affect aspects of Cerrado vegetation acting in conjunction with other modulators of the savanna physiognomy.
Descrição
Palavras-chave
Savana brasileira, Geada, Atributos morfo-fisiológicos, Brazilian savanna, Frost, Morphological and physiological attributes