ABSTRACT Background: Seasonally Dry Tropical Forests (SDTF) are recognized by their great biological diversity, but little is known about their temporal patterns, which may be crucial in a changing world. Here we aimed to characterize the SDTF dynamic patterns in floristic and structural changes, and also to evaluate shifts in dynamic rates and structural attributes such as richness, number of trees and biomass. Our hypothesis is that SDTF tree communities have their dynamic characterized by temporal fluctuations related to an instability pattern, in according to the already found for others tropical forests. For this we used a data of 42 400 m² plots in three fragments in the Brazilian Arboreal Caatinga, measured in 2005, 2010 and 2015. We evaluated temporal changes in richness, species composition, trees density, biomass and rates of tree mortality and recruitment; and also rates of biomass gain and loss. Results: We found a pattern of floristic composition stability, but with changes in structure and dynamics. There was a tree density decrease driven by constant mortality and by recruitment decrease, and biomass increase due to decrease in biomass loss and to increase in biomass gain. The biomass increase was main related to a small set of dominant species that are the most representative in the community dynamics. Conclusion: SDTF dynamics are related to stability in species composition, but with structural changes towards higher biomass stocks. The results are main related to community dynamics and to SDTF attributes such as climatic seasonality that drives the local ecological processes.

Resumo As novas condições ambientais impostas por eventos de distúrbios criam um mosaico de manchas em diferentes estágios sucessionais. Nosso objetivo foi descrever a variação temporal de uma floresta estacional semidecidual em função do histórico de perturbação antrópica, verificando possíveis mudanças na dinâmica e estrutura da floresta. Nós amostramos a vegetação arbórea com diâmetro a 1,3 m do solo (DAP) ≥ 5 cm em 15 parcelas permanentes de 20 × 20 m onde realizamos quatro inventários (2003, 2005, 2007 e 2015). Nós verificamos uma diminuição da densidade e aumento da área basal, o que indica que a comunidade arbórea analisada se encontra em estágio tardio de sucessão. A estrutura fitossociológica, a riqueza e a diversidade de espécies da comunidade arbórea não apresentaram mudanças ao longo dos monitoramentos. Entretanto, o predomínio da espécie Protium spruceanum pode ser uma resposta às mudanças ambientais provocadas pela mineração que ocorreu na área há 250 anos. As influências duradouras dos distúrbios antrópicos tornam este tipo de trabalho imprescindível por permitir a compreensão dos processos ecológicos, possibilitando um gerenciamento factual das florestas pelo manejo e conservação efetivos.

Abstract The new environmental conditions imposed by disturbance events often create a mosaic of spots in different successional stages. Our objective was to describe the temporal variation of a semideciduous seasonal forest based on its anthropic disturbance history, verifying possible changes in forest dynamics and structure. We sampled the arboreal vegetation with a diameter at breast height (1.3 m above the ground; DBH) ≥ 5 cm in 15 permanent plots of 20 × 20 m where we performed four inventories (2003, 2005, 2007 and 2015). We observed a density decrease and a basal area increase, which indicates the late successional stage of the analyzed tree community. The phytosociological structure, richness and species diversity of the tree community did not show changes throughout the monitoring. However, the Protium spruceanum predominance may be a response to the environmental changes caused by the mining occurred in the area 250 years ago. The anthropic disturbances enduring influences make this type of work indispensable because it allows the ecological processes understanding, allowing a factual management of the forests by the its effective management and conservation.

ABSTRACT The objective of this work was to evaluate if the soil heterogeneity expressed by the different soil classes would condition tree communities with different dynamic behaviors. The data were collected from 25 plots sized 20 × 20 (400 m²), 10 of them with Inceptisols, 9 with Ultisols, 5 with Entisols B and 1 with Entisols A. All individuals with DBH ≥ 5.0 cm in the plots were sampled in 2000, 2005, 2009 and 2015. Rates of mortality, recruitment, gain, loss and turnover dynamics in number of individuals and basal area were estimated for each soil class. The tree communities present in the soil classes showed no differences in the dynamic behavior to the point of expressing edaphic fragment heterogeneity. The differences are associated with stochastic fluctuations in rates caused by small disturbances, suggesting little influence of the soils on the dynamics of small-scale communities.