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We aimed to describe the floristic-structural organization, the richness and the phylogenetic structure of tree components in highland forest fragments in different successional stages, at São Joaquim National Park, in the municipality of Urubici, Santa Catarina state. Three fragments were selected, two in an advanced successional stage and one in an initial successional stage, being each one evaluated by 20 10 x 10 m sampling plots, allocated as 20 x 100 m transects. All trees with dbh ≥ 5 cm were identified and measured. The data were analyzed through rarefaction, multivariate ordination, indicator species analysis and phylogenetic structure metrics. There was no relationship between the richness and the successional stage, once the studied areas did not differ in relation to the number of species. The floristic-structural organization was influenced by the interaction between the successional stage and the environmental differences among areas. Phylogenetic clustering of species was observed in the initial successional stage area and random phylogenetic pattern was observed in advanced successional stage areas. The results indicated independent variation in richness in relation to successional phase and, that the forest succession influenced the floristic-structural composition and phylogenetic structure of the study areas.

RESUMO Investigar o padrão espacial das árvores, segundo suas classes de tamanho e segundo suas espécies mais abundantes pode fornecer evidências sobre a estrutura da comunidade vegetal, sendo que, o padrão espacial é uma questão-chave para estudos de ecologia florestal. O nível de organização espacial das árvores no ambiente depende de diversos processos ecológicos e características próprias de cada ambiente, de modo que a melhor compreensão deste quadro fornece subsídios importantes para o conhecimento sobre formações florestais. Neste trabalho objetivou-se estudar o padrão espacial das árvores, segundo suas classes de diâmetro e das quatro espécies mais abundantes em diferentes florestas, visando fornecer evidências sobre a ecologia de cada comunidade vegetal. A descrição do padrão espacial em cada formação florestal foi realizada segundo a Função K de Ripley. As formações florestais estudadas foram: Floresta Ombrófila, Cerradão, Floresta Estacional e Restinga. Instalou-se uma parcela de 10,24 ha em cada formação florestal, e todas as árvores com circunferência na altura do peito (CAP) a partir de 15 cm foram medidas, georreferenciadas e identificadas. Os resultados obtidos ressaltam o caráter agregado em florestas tropicais, como foi observado em todas as florestas estudadas. As árvores do Cerradão e da Restinga apresentaram padrões de agregação muito próximos. Para a Floresta Ombrófila, o padrão agregado foi significativo em toda a escala de distâncias estudada. Na Floresta Estacional, foi observada tendência à aleatoriedade, embora, uma agregação significativa tenha sido notada para curtas distâncias. O padrão espacial por classes de diâmetro foi, em linhas gerais, agregado para árvores menores que 10 cm de diâmetro, e entre 10 e 20 cm, e aleatório para as demais, evidenciando uma tendência de que árvores jovens são mais agregadas do que árvores adultas. O padrão espacial das espécies dominantes é sempre muito semelhante ao padrão geral de cada formação florestal. As diferenças entre o padrão espacial das espécies dominantes coincidentes entre as formações florestais indicam que seu padrão é influenciado por cada ambiente. Ressaltando-se assim, a importância da sua autoecologia e dos processos ecológicos intrínsecos a cada comunidade que podem explicar os padrões observados. ABSTRACT Investigating tree's spatial patterns according to their size classes and according to their more abundant species can provide evidences about the structure of the vegetal community, since the spatial pattern is a key question for forestry ecology studies. The tree spatial organization patterns on the environment depend on several ecological processes and on the specific characteristics of each environment, so that the best understanding of this frame provides important elements for the knowledge on forestry formation. This paper aimed to study tree spatial patterns, according to the diameter classes and from four most abundant species in different forests, in order to provide evidences regarding to the ecology of each vegetal community. The spatial pattern description in each forestry formation was developed using Ripley's K function. The studied forestry formations were: Ombrophilous Forest, Cerradao, Seasonal Forest and Restinga Forest. In this work, a 10.24 ha plot was installed in each forestry formation, and every tree, with a circumference at breast height (CBH) larger than 15 cm were measured, georeferenced and identified. The obtained data highlights the aggregated character in tropical forests, as observed in every studied forest. The 'Cerradão' and 'Restinga' forest trees showed close aggregate patterns. In the Ombrophilous forest, for all distance scales, the aggregate pattern was meaningful. In the seasonal forest, a random tendency was observed, although a meaningful aggregation was observed in all short distances. The spatial pattern by diameter classes was generally aggregated for trees smaller than 10 cm of diameter and between 10 and 20 cm and random for the others, proving the existence of a tendency which in young trees is more aggregated than in old ones. The spatial pattern of the dominant species is always strongly similar to the general pattern of each forestry formation. The differences between the spatial patterns of two or three coincident species, among the forestry formations, indicate that its pattern is influenced by each different environment. This stands out the importance of its self-ecology and of its ecological processes, intrinsic of each community that can explain the observed patterns.