Regeneração natural em pastagens abandonadas e sua correlação com variáveis ambientais e espaciais em diferentes métodos de restauração florestal no sul do Brasil

Abstract

Resumo: Nesta tese caracterizamos a composicao e estrutura da regeneracao natural de pastagens abandonadas submetidas a diferentes metodos de restauracao na Floresta Atlantica Subtropical, localizada no Faxinal do Bepe, Parque Nacional da Serra do Itajai - SC, de modo a investigar atributos relacionados com as variacoes floristicas e estruturais da vegetacao, bem como os padroes de distribuicao de especies lenhosas regenerantes em funcao de variaveis ambientais e espaciais. No Capitulo 1 (A composicao das especies lenhosas da Floresta Atlantica Subtropical varia em funcao do tipo de solo), o principal objetivo foi verificar se as variacoes na composicao e estrutura de uma floresta em estagio avancado de regeneracao estao relacionadas com o tipo de solo. Realizamos analises de ordenacao, calculamos os parametros fitossociologicos e detectamos as especies indicadoras para cada grupo floristico. No Capitulo 2 (Poucas especies lenhosas nativas dominantes: como age o processo de regeneracao da Floresta Atlantica Subtropical em pastagens abandonadas no Sul do Brasil), analisamos a composicao e estrutura das especies lenhosas da regeneracao natural de pastagens abandonadas. Calculamos os parametros fitossociologicos para as especies, indices de heterogeneidade e analisamos diagramas de Whittaker. No Capitulo 3 (Padroes floristicos da regeneracao natural da Floresta Atlantica Subtropical e suas implicacoes na restauracao florestal), investigamos se variaveis ambientais e espaciais predizem a variacao nos padroes de composicao de especies lenhosas regenerantes em pastagens abandonadas submetidas a diferentes metodos de restauracao. Efetuamos analises de ordenacao, similaridade e particao da variancia. Os resultados revelaram que a floresta em estagio avancado de regeneracao apresenta variacoes floristicas e estruturais em funcao do tipo de solo, alem de ser constituida por especies indicadoras para cada ambiente de solo analisado. A regeneracao natural da Floresta Atlantica Subtropical em pastagens abandonadas e caracterizada, predominantemente, por poucas especies lenhosas dominantes, e essas especies resultam em menor diversidade da vegetacao. A variacao na composicao de especies lenhosas regenerantes em pastagens abandonadas submetidas a diferentes metodos de restauracao esta relacionada a fatores ambientais (e.g., propriedades fisicas e quimicas dos solos). Contudo, verificamos que as variaveis espaciais - geralmente negligenciada em estudos sobre regeneracao de florestas subtropicais em pastagens abandonadas - desempenham um papel ainda mais relevante do que as proprias variaveis ambientais. Isso indica que a regeneracao florestal e predominantemente espacial, com destaque para processos bioticos e estocasticos. Finalmente, concluimos que a presente tese gerou importantes informacoes sobre o efeito do solo nos padroes floristicos da regeneracao natural de pastagens abandonadas submetidas a diferentes metodos de restauracao na Floresta Atlantica Subtropical, alem de mostrar os principais padroes de distribuicao das especies lenhosas ao longo de gradientes ambientais. Palavras-chave: Fitossociologia. Inventario florestal. Recuperacao de areas degradadas. Restauracao ecologica. Regeneracao florestal. Recuperacao florestal. Distribuicao de especies. Relacoes solovegetacao. Estrutura espacial. Particionamento da variancia.

Abstract: In this thesis we characterized the composition and structure of forest natural regeneration in abandoned pastures subjected to different restoration methods in the Subtropical Atlantic Rainforest, at Faxinal do Bepe, Parque Nacional da Serra do Itajai - SC, to investigate floristic and structural variations, and also the relationship among environmental/spatial variables and the distribution patterns of regenerating woody species. In the first chapter 1 (Subtropical Rainforest's woody species composition varies depending on the soil type), the main objective was to verify if the variations in composition and structure of a forest community in advanced successional stage are related to soil type. We conducted ordination analyses, calculated phytosociological parameters, and identified indicator species for each floristic group. In the second chapter (Few dominant native woody species: How the Subtropical Atlantic Rainforest's regeneration process develops in abandoned pastures in Southern Brazil?), we analyzed the composition and structure of natural regenerating woody species in abandoned pastures. We calculated the species' phytosociological parameters, heterogeneity index, and we also analyzed Whittaker diagrams. In the third chapter (Floristic patterns of the Atlantic Subtropical Rainforest natural regeneration and its forest restoration implications), we investigated if environmental and spatial variables predict variations in the composition of regenerating woody species in abandoned pastures subjected to different restoration methods. We performed ordination analyses, analysis of similarity, and variance partitioning. The results revealed that floristic and structural variations in forests in advanced regeneration stages are related to soil type; each soil type was related to a different set of indicator species. The natural regeneration of the Atlantic Subtropical Rainforest in abandoned pastures is characterized, predominantly, by few highly dominant woody species forming a community with reduced species diversity. The variation in the composition of regenerating woody species in abandoned pastures subjected to different restoration methods was shown to be related to environmental factors (e.g., soils' physical and chemical properties). However, we verified that the spatial variables - which are usually ignored in studies about the regeneration of subtropical rainforest in abandoned pastures - are stronger predictors than just the environmental variables. This suggests that forest regeneration in the studied area is driven mainly by spatial biotic/stochastic processes. Finally, we believe that this thesis generated important information about the influence of soil properties on floristic patterns of forest natural regeneration in abandoned pastures subjected to different restoration methods in the subtropical portion of the Subtropical Atlantic Rainforest. In addition, the main patterns of woody species distribution along environmental gradients were presented and discussed. Key-words: Phytosociology. Forest inventory. Recovery of degraded areas. Ecological restoration. Forest regeneration. Forest recovery. Species Distribution. Soil-vegetation relationship. Spatial structure. Variance partitioning.