Estratégias de persistência e regeneração em campo sujo de Cerrado após o fogo
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Data
2017-05-12
Autores
Zupo, Talita Marques [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Em ambientes onde ocorre o fogo, as espécies de plantas podem regenerar via rebrote, semente ou através de ambas as estratégias. Os mecanismos de regeneração são favorecidos ou limitados tanto pelas condições ambientais (produtividade e disponibilidade de recursos) quanto pelo regime de queima, incluindo sua frequência e época. Assim, o objetivo principal desta tese foi investigar a regeneração pós-fogo de espécies de uma comunidade de campo sujo de Cerrado localizada na Reserva Natural Serra do Tomabdor (Goiás). Avaliamos o papel da regeneração via rebrote e via semente e procuramos avaliar os fatores que estão envolvidos no rebrote das plantas após serem submetidas a diferentes tipos de distúrbio, e distúrbios que ocorreram em diferentes frequências e épocas do ano, visto que tanto o tipo do distúrbio quanto a época e a frequência em que ele ocorre podem afetar a regeneração das plantas. Verificamos que o rebrotamento é a principal estratégia de regeneração pós-fogo, ocorrendo principalmente a partir de gemas localizadas em estruturas subterrâneas que estão altamente protegidas pelo solo, e que o recrutamento via semente tem um papel pequeno na regeneração. No entanto, a tolerância das sementes a altas temperaturas é uma característica importante que permite o recrutamento quando as condições ambientais forem favoráveis. Também verificamos que as respostas pós-fogo, relacionadas tanto com o rebrote como com a floração, estão relacionadas com a disponibilidade de recursos no ambiente pós-fogo. A regeneração mais devagar das plantas queimadas no inicio da estação seca está provavelmente relacionada com o maior número de meses que estas plantas foram sujeitas a déficit hídrico, sendo que, após a estação chuvosa, as plantas queimadas nas diferentes épocas do ano apresentaram tamanhos similares. A regeneração após três queimas consecutivas não foi diferente da regeneração após queimas com intervalos maiores, sugerindo que a quantidade de reservas armazenadas não foi um fator limitante. Além disso, o fogo induziu a floração das espécies em relação a plantas não queimadas, sugerindo que o fogo é um fator importante na reprodução das espécies.
In fire-prone ecosystems, plant species can persist by resprouting, recruiting from seeds, or use both strategies. Such regeneration mechanisms can be favored or limited by both environmental conditions (site productivity and resource availability) and fire regimes, such as fire frequency and season. The aim of this thesis was investigate the post-fire regeneration mechanism of Cerrado plant species from an open savanna community located at the Reserva Natural Serra do Tombador (Goiás, Central Brazil). Thus, we evaluated the role of post-fire resprouting and post-fire seeding as regeneration mechanisms in Cerrado open savannas. Moreover, we evaluated the factors driving resprouting responses after plants are subjected to different disturbance types and to disturbances in different seasons and frequencies. We verified that resprouting is the main post-fire regeneration mechanism in Cerrado, originating mainly from buds located in underground structures, and that post-fire seeding plays a minor role in the post-fire regeneration of this community. However, seed tolerance is an important seed trait as it allows for seed germination and recruitment when favorable environmental conditions arise. Our results suggest that post-fire resprouting is driven mainly by availability of resources present in the post-fire environment. The slower recovery of plants burned during early-dry season fires is most likely related to the prolonged exposure to water deficits as plants endured all five months of the dry season. However, after the rainy season, plants burned in the different fire seasons had similar sizes. We found no difference in resprouting responses between annually and biennially burned plants, and plants resprouted vigorously after three consecutive burns, suggesting that amount of stored reserves was not a limiting factor. Moreover, fire induced flowering in most species in relation to unburnt plants, suggesting fire is an important factor for the reproduction of these species.
In fire-prone ecosystems, plant species can persist by resprouting, recruiting from seeds, or use both strategies. Such regeneration mechanisms can be favored or limited by both environmental conditions (site productivity and resource availability) and fire regimes, such as fire frequency and season. The aim of this thesis was investigate the post-fire regeneration mechanism of Cerrado plant species from an open savanna community located at the Reserva Natural Serra do Tombador (Goiás, Central Brazil). Thus, we evaluated the role of post-fire resprouting and post-fire seeding as regeneration mechanisms in Cerrado open savannas. Moreover, we evaluated the factors driving resprouting responses after plants are subjected to different disturbance types and to disturbances in different seasons and frequencies. We verified that resprouting is the main post-fire regeneration mechanism in Cerrado, originating mainly from buds located in underground structures, and that post-fire seeding plays a minor role in the post-fire regeneration of this community. However, seed tolerance is an important seed trait as it allows for seed germination and recruitment when favorable environmental conditions arise. Our results suggest that post-fire resprouting is driven mainly by availability of resources present in the post-fire environment. The slower recovery of plants burned during early-dry season fires is most likely related to the prolonged exposure to water deficits as plants endured all five months of the dry season. However, after the rainy season, plants burned in the different fire seasons had similar sizes. We found no difference in resprouting responses between annually and biennially burned plants, and plants resprouted vigorously after three consecutive burns, suggesting that amount of stored reserves was not a limiting factor. Moreover, fire induced flowering in most species in relation to unburnt plants, suggesting fire is an important factor for the reproduction of these species.
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Palavras-chave
Ecologia vegetal, Ecologia de fogo, Regime de fogo, Rebrotamento, Germinação