Os Corredores de Biodiversidade têm a função de manter e restabelecer a conectividade entre fragmentos florestais remanescentes. O Corredor de Biodiversidade Santa Maria - PR visa conectar o Parque Nacional do Iguaçu à mata ciliar do reservatório de Itaipu, através da implantação de áreas de reflorestamento entre fragmentos remanescentes de Floresta Estacional Semidecidual. Este trabalho objetivou avaliar a diversidade de espécies arbóreas e a similaridade florística entre áreas de florestas nativas secundárias e de reflorestamentos em diferentes idades. Compararam-se a densidade, a diversidade, a equabilidade e a composição florística dos cinco fragmentos e a similaridade foi avaliada pelos índices de Jaccard e de distância de Bray-Curtis. Em dois hectares amostrados, foram encontrados 2328 indivíduos, distribuídos em 134 espécies e 39 famílias. A similaridade florística agrupou as florestas secundárias nativas mais preservadas e as áreas com reflorestamento em grupos distintos. As 11 espécies exóticas encontradas nas áreas de reflorestamento não foram observadas nas áreas mais preservadas e, portanto, o manejo das mesmas deve ser incentivado, como medida de preservação dos fragmentos nativos remanescentes de Floresta Estacional Semidecidual.

Climatic factors can influence the establishment and growth of wood species, but little is known about the effect of these factors on monodominant communities in wetlands. Therefore, we asked how climatic factors, such as ENSO (El Niño-Southern Oscillation), precipitation and flooding, influence growth and establishment of the dominant speciesErythrina fuscain the Pantanal. We determined the age of sampled individuals, the age of the population and evaluated the effects of climate on tree growth. We obtained samples for dendrochronological analyses using destructive (seven individuals) and non-destructive methods. We cross-dated and built a chronology, correlating results with climatic factors. We sampled 0.6 ha of the population and separated individuals into diameter classes to determine age based on diameter/age ratio obtained through dendrochronological analyses. We obtained a chronology with individuals up to 34 years old, while in the population sample, the oldest individual was 54 years old. The factors that influenced growth during the study period were precipitation (positive correlation) andEl Niño(negative correlation).E. fuscaindividuals seem to grow more during the period of highest precipitation, andEl Niñoevents reduce precipitation in the Pantanal, resulting in a decrease in the growth ofE. fuscaindividuals. We detected a decrease of young individuals in the last nine years, which seems to be related to the decrease in minimum flood levels. This indicates a future decline in the number of individuals. These results allow us to propose measures to protect these monodominant formations, which mainly involve avoiding further anthropic activities, that could reduce flooding levels.

The perturbation of Neotropical forests generates large disturbances in biological communities. The species that suffer least from the resulting habitat fragmentation are the pioneers, because they possess greater ability to inhabit disturbed environments. Therefore, it is expected that species diversity will be greater in areas subjected to intermediate disturbance, such as the opening of gaps, because a large number of pioneer species will develop and coexist with species of more advanced successional stages. This study aimed to compare two forest remnants that differed in size and disturbance intensity, in order to determine the effects of disturbances on species diversity and the size ratios of individual trees. This was accomplished with comparative analyses of diversity, richness and diameter ratios obtained for 10 plots at two semideciduous forest sites. We recorded a total of 85 species, of which 70 were in the private nature reserve Fazenda Santa Maria, 58 were in Iguaçu National Park, and 43 were at both sites. Diversity was greater in the more disturbed remaining forest, because this area showed higher species richness, which is in accordance with some premises of the intermediate disturbance theory. There was also an increase in the number of pioneer individuals, and the less disturbed area showed individuals with larger diameters, which is likely attributable to the removal of large individuals from the more disturbed area during the anthropogenic process of forest modification