Abstract This study aimed at evaluating and compare the changes from 2012 to 2016 in the structure and floristic composition of a remnant Araucaria Forest. The entry and mortality rates were 2.2% year-1 and 6.9% year-1, respectively. Among the most represented species, those with the greatest yearly increases in their numbers were Sebastiania brasiliensis, Eugenia uniflora, and Allophylus sp. Average mortality density was 498 ind ha-1, and was particularly high for the following species: Casearia decandra (representing 32.3% of total mortality), Eugenia sp. (27.2%), Cinnamodendron dinisii (24.5%), and Lithraea brasiliensis (25.2%). The pioneer species represented 8.33% of income and 29.17% mortality, and secondary species composed 33.33% and 62.50% of income and mortality, respectively. Climax species accounted for 8.33% of income and did not contribute to mortality. The high tree mortality observed in the present study can be attributed, among others factors, to the effects of natural disturbance that occurred in the period.

Resumo O presente estudo teve como objetivo avaliar as alterações ocorridas, no período de 2012 a 2016, na estrutura da regeneração natural de um remanescente de Floresta Ombrófila Mista, sem intervenções há mais de 40 anos. Em relação a dinâmica da composição florística da regeneração natural, houve a saída de 18 espécies (23,38% do total) e a entrada de 27 novas espécies (35,06% do total). Os maiores acréscimos foram observados para Allophylus edulis, Myrsine umbellata e Miconia cinerascens. Analisando a dinâmica da regeneração em grupos ecológicos, observou-se que as espécies pioneiras tiveram um valor similar em ambos os levantamentos (29,4 a 29,6%). As espécies secundárias decresceram de 56,6% para 52,8%. E as espécies de sucessão tardia aumentaram de 0,2 a 6,0%. Logo, o remanescente estudado encontra-se em fase de cicatrização de distúrbio, caracterizada pelo aumento da regeneração de espécies pioneiras, uma vez que há quantidade suficiente de luminosidade incidindo no interior da floresta.

Abstract This study evaluated changes in the structure for remnant Mixed Ombrophilous Forest recovering from logging, which ceased over 40 years ago. Regarding the dynamics of the floristic composition of natural regeneration, 18 species remained (23.38% of the total) and 27 new species entered (35.06% of the total). The greatest increases were observed for Allophylus edulis, Myrsine umbellata, and Miconia cinerascens. When analyzing the dynamics of regeneration in ecological groups, it was observed that pioneer species had a similar value in both surveys (29.4% and 29.6%); secondary species decreased from 56.6% to 52.8%, and late-successional species increased from 0.2% to 6.0%. Therefore, the forest fragment studied is in a healing phase after disturbance, characterized by the increased regeneration of pioneer species as a result of sufficient light entering the interior of the forest.