Quantas vezes devemos queimar o Cerrado? O efeito da frequência do fogo em comunidades vegetais de campo sujo de Cerrado
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Data
2019-11-29
Autores
Rodrigues, Cassy Anne dos Santos [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O Cerrado é formado por fisionomias campestres e savânicas, evoluiu na presença do fogo e depende dele para manter suas fisionomias e biodiversidade. O regime de fogo influencia diretamente na montagem da comunidade vegetal, na regeneração e nas habilidades competitivas das plantas. A frequência é um dos fatores do regime de fogo e alterações nela podem ser prejudiciais até mesmo para plantas e comunidades adaptadas ao fogo. Portanto, este estudo busca compreender os efeitos de diferentes frequências de fogo em comunidades de campo sujo de Cerrado. Para isso, foram realizados levantamentos da vegetação e coleta de biomassa em áreas com diferentes históricos de fogo (excluído do fogo, queimadas anualmente e bienalmente), o que forneceu os dados de composição e produtividade da comunidade. Os levantamentos, incluindo a cobertura (%) por espécie, foram realizados em 10 subparcelas de 1x1m por tratamento (10 subparcelas/tratamento,3 tratamentos, 4 parcelas/tratamento). Avaliamos também através da taxa de propagação (m.s-1), eficiência de queima (%) e intensidade (kW.m-1) entre outros parâmetros do fogo, os efeitos de diferentes frequências no comportamento do fogo. Nossos resultados mostraram que a riqueza de espécies das comunidades vegetais foi maior nas áreas com frequência anual de fogo do que nas excluídas, 6 meses após o fogo e maior para as bienais do que as excluídas 12 meses após o fogo. O índice de diversidade foi maior no tratamento anual de queima antes e 12 meses após as queimas. Quanto ao número de espécies por grupo funcional, apenas as herbáceas apresentaram aumento e apenas nas parcelas com queimas. Além disso, encontramos diferenças na porcentagem de cobertura de acordo com a forma de crescimento, apenas as herbáceas entre os tratamentos de queima e as parcelas de exclusão. Em relação à cobertura, são as porcentagens de biomassa morta e solo nu que variam entre os históricos de fogo. As parcelas com menor frequência de queima apresentaram cerca de 7 vezes mais cobertura de biomassa morta do que os outros tratamentos. Estes resultados sugerem que 6 anos de exclusão de fogo começam a causar perda e mudanças no padrão de cobertura das espécies. Quanto ao comportamento do fogo encontramos para as comunidades com queimas anuais menos biomassa morta e total e porcentagens mais altas de solo nu do que com queimas bienais. Quanto aos parâmetros de queima, a intensidade, altura da chama, temperaturas máximas e tempo de permanência foram menores nas parcelas anuais. Maior frequência de fogo mudou a estrutura da vegetação e os parâmetros de queima responderam a essas mudanças. Concluímos que a frequência da queima influencia o comportamento do fogo, afetando o aumento da biomassa morta. As comunidades vegetais sob queimas anuais não acumularam a mesma quantidade de biomassa morta que as bienais e, portanto, elas têm porcentagens mais altas de solo nu. Essa combinação afeta o comportamento do fogo devido a uma diminuição e descontinuidade da carga de combustível disponível, o que dificulta a sustentação e a propagação do fogo. Assim, buscou-se através deste estudo compreender a influência e importância da frequência do fogo na dinâmica e montagem de comunidades vegetais de Cerrado, bem como no comportamento do fogo. O que deve contribuir com o desenvolvimento de estratégias de manejo de fogo para conservação deste ecossistema.
The Cerrado is formed by grasslands and savannah physiognomies, evolved in the presence of fire and depends on it to maintain its physiognomies and biodiversity. The fire regime influences the plant community assembly, the regeneration and the competitive abilities of the plants. Frequency is one of the factors of the fire regime and changes in it can be detrimental even to fire-adapted plants and communities. Therefore, this study aimed to understand the effects of different fire frequencies in campo sujo of Cerrado communities. For this, vegetation surveys and biomass collection were carried out in areas with different fire histories (excluded from fire, burned annually and biennially), which provided community composition and productivity data. Surveys, including coverage (%) by species, were performed on 10 1x1m subplots per treatment (10 subplots / treatment, 3 treatments, 4 plots / treatment). We also evaluated through propagation rate (m.s-1), firing efficiency (%) and intensity (kW.m-1) among other fire parameters, the effects of different frequencies on fire behavior. Our results showed that species richness of plant communities was higher in areas with annual fire frequency than in excluded areas 6 months after fire and higher for biennials than those excluded 12 months after fire. The diversity index was higher in the annual burn treatment before and 12 months after the burns. Regarding the number of species per functional group, only the forbs presented increase and only in the plots with burns. Moreover, we found differences in the percentage of coverage according to the growth form, only the forbs between the burn treatments and the exclusion fire plots. Regarding the cover, the percentages of dead biomass and bare soil vary among fire histories. The plots with lower burning frequency showed about 7 times more dead biomass coverage than the other treatments. These results suggest that 6 years of fire exclusion begin to cause loss and changes in species cover pattern. Regarding fire behavior, we found for communities with annual burns less dead and total biomass and higher percentages of bare soil than with biennial burns. Regarding the burning parameters, the intensity, flame height, maximum temperatures and residence time were lower in the annual plots. Higher frequency of fire changed vegetation structure and burning parameters responded to these changes. We conclude that the frequency of burning influences fire behavior, affecting the increase of dead biomass. Plant communities under annual burns have not accumulated the same amount of dead biomass as biennial burns, therefore they have higher percentages of bare soil. This combination affects the fire behavior due to a decrease and discontinuity of available fuel load, which makes it difficult to sustain and spread the fire. Thus, we aimed through this study to understand the influence and importance of fire frequency on the dynamics and assembly of Cerrado plant communities, as well as on the behavior of fire. This should contribute to the development of fire management strategies for the conservation of this ecosystem.
The Cerrado is formed by grasslands and savannah physiognomies, evolved in the presence of fire and depends on it to maintain its physiognomies and biodiversity. The fire regime influences the plant community assembly, the regeneration and the competitive abilities of the plants. Frequency is one of the factors of the fire regime and changes in it can be detrimental even to fire-adapted plants and communities. Therefore, this study aimed to understand the effects of different fire frequencies in campo sujo of Cerrado communities. For this, vegetation surveys and biomass collection were carried out in areas with different fire histories (excluded from fire, burned annually and biennially), which provided community composition and productivity data. Surveys, including coverage (%) by species, were performed on 10 1x1m subplots per treatment (10 subplots / treatment, 3 treatments, 4 plots / treatment). We also evaluated through propagation rate (m.s-1), firing efficiency (%) and intensity (kW.m-1) among other fire parameters, the effects of different frequencies on fire behavior. Our results showed that species richness of plant communities was higher in areas with annual fire frequency than in excluded areas 6 months after fire and higher for biennials than those excluded 12 months after fire. The diversity index was higher in the annual burn treatment before and 12 months after the burns. Regarding the number of species per functional group, only the forbs presented increase and only in the plots with burns. Moreover, we found differences in the percentage of coverage according to the growth form, only the forbs between the burn treatments and the exclusion fire plots. Regarding the cover, the percentages of dead biomass and bare soil vary among fire histories. The plots with lower burning frequency showed about 7 times more dead biomass coverage than the other treatments. These results suggest that 6 years of fire exclusion begin to cause loss and changes in species cover pattern. Regarding fire behavior, we found for communities with annual burns less dead and total biomass and higher percentages of bare soil than with biennial burns. Regarding the burning parameters, the intensity, flame height, maximum temperatures and residence time were lower in the annual plots. Higher frequency of fire changed vegetation structure and burning parameters responded to these changes. We conclude that the frequency of burning influences fire behavior, affecting the increase of dead biomass. Plant communities under annual burns have not accumulated the same amount of dead biomass as biennial burns, therefore they have higher percentages of bare soil. This combination affects the fire behavior due to a decrease and discontinuity of available fuel load, which makes it difficult to sustain and spread the fire. Thus, we aimed through this study to understand the influence and importance of fire frequency on the dynamics and assembly of Cerrado plant communities, as well as on the behavior of fire. This should contribute to the development of fire management strategies for the conservation of this ecosystem.
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Palavras-chave
Comportamento do fogo, Intensidade do fogo, Quantidade de material combustível, Distribuição do material combustível, Composição da comunidade vegetal, Regeneração pós-fogo, Fire behavior, Fire intensity, Amount of fuel load, Distribution of fuel load, Composition of the plant community, Post-fire regeneration