Conversão de talhões de eucalipto em Mata Atlântica: efeitos da intensidade de desbaste na vegetação nativa
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Data
2020-05-28
Autores
Onofre, Felipe Ferreira [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A conversão de florestas homogêneas de eucalipto em floresta nativa tem se tornado uma necessidade comum, principalmente na região sudeste do país, em atendimento não só à legislação ambiental, mas também aos preceitos da certificação florestal. Entretanto, embora se observe que em muitos casos a vegetação nativa seja capaz de se regenerar naturalmente no interior de talhões de eucalipto, ainda não há evidências experimentais suficientes a respeito de qual o melhor método de manejo para acelerar e otimizar este processo. Objetivamos, com esta pesquisa, poder definir estratégias e métodos de manejo para a restauração da Mata Atlântica (Floresta Ombrófila Densa) em antigas unidades de produção (talhões) de Eucalyptus sp., testando a efetividade de alguns tratamentos de raleamento dos talhões na aceleração da regeneração natural da vegetação nativa. Além disso, almejamos compreender os padrões (trajetórias sucessionais) e filtros ecológicos que direcionam a montagem da comunidade regenerante nesses talhões de eucalipto sob diferentes intensidades de manejo. A pesquisa foi realizada no Parque das Neblinas, município de Bertioga, SP, em um talhão comercial de plantio de Eucalyptus saligna Smith em terceira rotação que havia sido abandonado e se encontra em processo de sucessão natural. O delineamento do experimento foi em blocos ao acaso, onde foram aplicados em maio de 2005, seis tratamentos (T1 - testemunha, T2, T3, T4, T5 redução respectivamente de 25, 50, 75 e 100% da área basal das árvores por meio da morte em pé, e T6 - corte raso) com 4 repetições (blocos) e parcelas experimentais de 20 X 40 metros. Após 14 anos do manejo inicial, avaliamos a estrutura, riqueza e diversidade da comunidade regenerante e característica da serapilheira acumulada sobre o solo. Os resultados foram submetidos a análises de variância. Os tratamentos silviculturais surtiram efeito significativo positivo na regeneração natural da vegetação nativa para as duas classes de regeneração natural estudadas (DAP ≥ 5 cm e DAP < 5 cm), principalmente para a regeneração com DAP ≥ 5 cm, promovendo para os tratamentos T3 e T4, melhores resultados em riqueza e diversidade e para os tratamentos T5 e T6 melhores resultados em estrutura, quando comparados aos outros tratamentos e ao controle (T1). A biomassa de serapilheira acumulada (fração folhas e galhos finos) sofreu efeito significativo dos tratamentos, sendo menor nos tratamentos T5 (redução de 100% da área basal) e T6 (corte raso), os quais se equipararam à serapilheira acumulada no solo na mata nativa de referência. Os teores dos nutrientes, não sofreram efeito dos tratamentos, entretanto a quantidade de macronutrientes e micronutrientes aportada na serapilheira se diferiu entre os tratamentos. Não houve efeito significativo na relação C:N entre os tratamentos, entretanto houve efeito significativo entre todos os tratamentos e a mata nativa. A técnica de manejo florestal apresentado é uma ferramenta promissora quando o objetivo é a restauração da estrutura e diversidade nestes ambientes, promovendo uma recuperação mais rápida da vegetação nativa e pode ser adaptada, dependendo do contexto ambiental, e uma análise de custo-benefício.
The conversion of homogeneous eucalyptus forests into native forest has become a common need, especially in the southeastern region of the country, in compliance not only with environmental legislation, but also with of forest certification principles. However, although in many cases the native vegetation is able to naturally regenerate inside eucalyptus stands, there is still insufficient experimental evidence to recommend the best management method to accelerate and optimize this process. We aimed at to define management strategies and methods for the restoration of the Atlantic Forest (Tropical Wet Forest) in old production units (stands) of Eucalyptus sp., testing the effectiveness of some thinning treatments in the acceleration of natural regeneration of the native vegetation. In addition, we aimed at to understand the patterns (successional trajectories) and ecological filters that guide the assembly of the regenerating community in these eucalyptus stands under different management intensities. The research was carried out at Parque das Neblinas, municipality of Bertioga, SP, in a commercial plantation stands of Eucalyptus saligna Smith in third rotation that had been abandoned and is in the process of natural succession. The experiment was designed in a randomized block design, in which six treatments were applied in May 2005 (T1 - control, T2, T3, T4, T5, reduction of 25, 50, 75 and 100% of the basal area of trees through standing death, and clear cut) with 4 replicates (blocks) and experimental plots of 20 X 40 meters. After 14 years of initial management, we evaluated the structure, richness and diversity of the regenerating community and soil litter characteristics. The silvicultural treatments had a significant positive effect on the natural regeneration of native vegetation for the two classes of natural regeneration (DBH ≥ 5 cm and DBH <5 cm), mainly for the size class with DBH ≥ 5 cm, promoting for treatments T3 and T4, better results in richness and diversity and for the treatments T5 and T6 better results in forest structure, when compared to the other treatments and the control (T1). The accumulated litter biomass (fraction of leaves and thin branches) was affected by the treatments, with higher average values for the T1 - control treatment, compared to the T5 and T6 treatment (100% and clear cut), that equaled the native forest. The nutrient contents were not affected by the treatments, however the amount of macronutrients and micronutrients in the litter differed between the treatments, which presented higher values for T1 (control), intermediate values for T2, T3 and T4, lower values for T5 and T6, and even smaller for native forest. There was no significant effect on the relation C:N between treatments, but there was a significant effect between the whole treatments and native forest. The forest management technique presented is a promising tool when the objective is to restore structure and diversity in these environments, promoting a faster recovery of native vegetation and can be adapted, depending on the environmental context and a cost-benefit analysis.
The conversion of homogeneous eucalyptus forests into native forest has become a common need, especially in the southeastern region of the country, in compliance not only with environmental legislation, but also with of forest certification principles. However, although in many cases the native vegetation is able to naturally regenerate inside eucalyptus stands, there is still insufficient experimental evidence to recommend the best management method to accelerate and optimize this process. We aimed at to define management strategies and methods for the restoration of the Atlantic Forest (Tropical Wet Forest) in old production units (stands) of Eucalyptus sp., testing the effectiveness of some thinning treatments in the acceleration of natural regeneration of the native vegetation. In addition, we aimed at to understand the patterns (successional trajectories) and ecological filters that guide the assembly of the regenerating community in these eucalyptus stands under different management intensities. The research was carried out at Parque das Neblinas, municipality of Bertioga, SP, in a commercial plantation stands of Eucalyptus saligna Smith in third rotation that had been abandoned and is in the process of natural succession. The experiment was designed in a randomized block design, in which six treatments were applied in May 2005 (T1 - control, T2, T3, T4, T5, reduction of 25, 50, 75 and 100% of the basal area of trees through standing death, and clear cut) with 4 replicates (blocks) and experimental plots of 20 X 40 meters. After 14 years of initial management, we evaluated the structure, richness and diversity of the regenerating community and soil litter characteristics. The silvicultural treatments had a significant positive effect on the natural regeneration of native vegetation for the two classes of natural regeneration (DBH ≥ 5 cm and DBH <5 cm), mainly for the size class with DBH ≥ 5 cm, promoting for treatments T3 and T4, better results in richness and diversity and for the treatments T5 and T6 better results in forest structure, when compared to the other treatments and the control (T1). The accumulated litter biomass (fraction of leaves and thin branches) was affected by the treatments, with higher average values for the T1 - control treatment, compared to the T5 and T6 treatment (100% and clear cut), that equaled the native forest. The nutrient contents were not affected by the treatments, however the amount of macronutrients and micronutrients in the litter differed between the treatments, which presented higher values for T1 (control), intermediate values for T2, T3 and T4, lower values for T5 and T6, and even smaller for native forest. There was no significant effect on the relation C:N between treatments, but there was a significant effect between the whole treatments and native forest. The forest management technique presented is a promising tool when the objective is to restore structure and diversity in these environments, promoting a faster recovery of native vegetation and can be adapted, depending on the environmental context and a cost-benefit analysis.
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Palavras-chave
Mata Atlântica, Restauração Florestal, Biodiversidade, Manejo adaptativo, Floresta Ombrófila Densa, Sucessão Florestal, Atlantic Forest, Forest Restoration, Biodiversity, Adaptative management, Humid Rain Forest, Forest Succession