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 Este estudo objetivou caracterizar a dinâmica, além das mudanças estruturais e florísticas em uma comunidade arbórea de Floresta Estacional Decidual, no Norte de Minas Gerais no intervalo de cinco anos. Em 2005, foram alocadas 10 parcelas de 20x20m. Os indivíduos com CAP ≥ 10 cm foram marcados com etiquetas numeradas e mensurados. Em 2010, no segundo inventário, foram incorporados os recrutas, registrados os mortos e remedidos os sobreviventes. Em 2005 foram registradas 46 espécies, e em 2010 foram 45 espécies. O índice de Shannon-Wienner (H’ = 2,62 nats ind-1 em 2005; H’ = 2,60 nats ind-1 em 2010) e a equabilidade de Pielou (J = 0,683 em 2005; J = 0,682 em 2010) não apresentaram diferenças significativas. Foram registrados ao todo 57 indivíduos mortos, com taxa de mortalidade média de 1,64% ano-1. Enquanto ocorreram 18 recrutas, apresentando taxa de recrutamento médio de 0,53% ano-1. Apesar da maior mortalidade, em comparação com o recrutamento, os resultados sugerem que a comunidade se manteve estável tanto em termos estruturais e de diversidade no intervalo considerado.

ABSTRACT This study aimed to characterize the dynamics, structural changes and floristics of a Northern Minas Gerais Seasonally Deciduous Forest tree community, in a 5 year interval. In 2005, 10 (20 x 20m) plots were allocated. All trees (CBH ≥ 10 cm) were tagged and measured. A second census was carried out in 2010 in order to measure surviving, new recruits and dead trees. In 2005, 46 species were recorded, moving to 45 in 2010. No significant differences were found for Shannon - diversity (H’ = 2.62 nats ind-1 in 2005; H’ = 2.60 nats ind-1 in 2010) and Pielou eveness (J = 0.683 in 2005; J = 0.682 in 2010) in the interval. A total of 57 dead records (rate of 1.64% year-1) were found whereas 18 trees were recruited (rate of 0.53% year-1). Despite the higher mortality as compared to recruitment, the results suggest that the community remained stable in both structural and diversity terms in the interval considered.

A maior parte dos estudos envolvendo as Florestas Tropicais Sazonalmente Secas aborda questões fitogeográficas e conexões florísticas deste bioma disjunto. Porém, pouco se conhece a respeito das características estruturais da FTSS. Devido a esta lacuna existente na literatura, buscamos descrever a estrutura de um fragmento remanescente de FTSS em uma área ecotonal entre domínio do Cerrado e da Caatinga. Ocorreram no estudo grande número de espécies arbóreas, 79, e altos valores para os índices de diversidade e equabilidade (3,6 nats/indivíduos e 0,83, respectivamente). A distribuição diamétrica para os indivíduos que apresentaram maiores valores de cobertura e para a comunidade não resultou em padrão de J-reverso, o que indica adaptações ecológicas ao stress hídrico adotadas em diferentes estratégias de crescimento. Não houve formação de grupos florísticos, já que a alta fertilidade do solo da área de estudo configura um ambiente homogêneo. A característica da área de estudo detectada através da estrutura, associada a dados edáficos, nos permitiu vislumbrar sua importância em termos de conservação e reforçar a importância de estudos com este enfoque nas FTSS.

Most studies on Seasonally Dry Tropical Forests (SDTFs) investigate phytogeographic patterns and floristic connections of this disjunct biome. However, little is known about the structural characteristics of SDTFs. We aimed to describe the structure of a SDTF in an ecotonal area between the Cerrado and Caatinga domains. In total, 79 tree species were recorded, and high values of Shannon diversity index (3.6 nats/individual) and equability (0.83) were observed. The diameter distribution for the species with higher cover values and for the entire community did not exhibit a reverse-J shaped distribution, which indicates the occurrence of different growth strategies and ecological adaptations to water stress. The results did not indicate the formation of floristic groups, as the high soil fertility in the study area results in a homogeneous environment. The structural characteristics of the study area associated with the soil composition highlight its importance for conservation and emphasize the need for community structure studies in SDTFs.

Devido à heterogeneidade fitofisionômica da vegetação na região Norte Mineira, a estrutura e riqueza de seus remanescentes são consideravelmente variáveis, e, embora pouco conhecida, trata-se de uma região amplamente explorada economicamente. Objetivou-se, com este estudo, caracterizar a estrutura e florística de uma área de caatinga arbórea, localizada em Juvenília, Minas Gerais. Foram alocadas 20 parcelas de 20 × 20 m (400 m²) totalizando 0,8 há. Nelas foram mensurados todos os indivíduos com CAP (circunferência à altura do peito) > 10 cm. Para complementar a listagem florística do componente arbustivoarbóreo, foram realizadas quatro visitas para coleta de material botânico entre janeiro e dezembro de 2003. A composição florística foi representada por 64 espécies arbóreas, destas, 47 foram amostradas no levantamento fitossociológico. A diversidade da área foi de H' = 2,90 e J' = 0,76, com dominância das espécies Anadenanthera colubrina, Poincianella pluviosa e Myracrodruon urundeuva que apresentaram os maiores valores de Dominância: 26,3, 13,1 e 20,3%; Densidade: 11,2, 16,6 e 10,1%; Frequência: 6,2, 6,5 e 5,5% e Valor de Importância: 14,6, 12,1 e 12,0%, respectivamente. A distribuição diamétrica da comunidade tendeu à normalidade, com menor quantidade de indivíduos nas classes diamétricas menores e maiores. A comunidade estudada mostra padrões estruturais e florísticos semelhantes a outros remanescentes de florestas deciduais em bom estado de conservação, dentro e fora do bioma Caatinga, embora tenha sido evidenciada a presença de interferências antrópicas na área.

Due to the phytophysiognomic heterogeneity of the northern Minas Gerais region, the structure and richness of local vegetation remnants vary considerably, and regardless of the fact that the region is yet little known, it has been widely explored economically. The objective of this study is to characterize the structure and floristics of a fragment of Arboreous Caatinga located in Juvenília, Minas Gerais. Twenty 20 × 20m plots (400 m²) were allocated, to a total of 0.8 ha, and all individuals in them with a CAP (circumference at breast height) > 10 cm were recorded. To complement the floristic listing of shrub and tree components, four visits were undertaken to collect botanical material, between January and December 2003. The floristic composition was represented by 64 arboreous species, out of which 47 were sampled in the phytosociological survey. The local diversity was H' = 2.90 and J' = 0.76, with a dominance of species Anadenanthera colubrina, Poincianella pluviosa and Myracrodruon urundeuva, respectively with Dominance: 26.3%, 13.1% and 20.3%; Density: 11.2%, 16.6% and 10.1%; Frequency: 6.2%, 6.5% and 5.5% and Importance Value: 14.6%, 12.1% and 12.0%. The diameter distribution of the community tended to normality, with less individuals in smaller and larger diameter classes. The structural and floristic patterns of the community in question were found to be similar to other reasonably preserved remnants of deciduous forest, inside and outside the Caatinga biome, despite the evidence of local anthropic intervention.