Influência do regime de alagamento sobre as variações temporais na estrutura em comunidades arbóreas

Abstract

The dynamics of forests is known to be influenced by processes of disturbances and changing environmental conditions, and data sets that provide a long-term perspective, and can allow an assessment of dynamic processes in topographic gradients are highly valuable. This study assess the dynamics of a flood-prone riverine semideciduous seasonal forest along a topographic gradient in the municipality of Madre de Deus de Minas – MG during a 23-year monitoring period (1991 - 2014). The following is hypothesized: (a) temporal changes in community diversity and structure occur according to the different habitats along the topographic gradient because river flooding are important sources of disturbance; (b) tree community dynamics is different among habitats and riverine patches are more unstable through time. The aim of the study was to analyse the tree community dynamics, focused on temporal variation in forest composition, structure and diversity within and among habitats which also reflects topographic clusters of the semideciduous seasonal forest remnant. The tree community survey was carried out at 71 contiguous permanent plots (1.597 ha) established in a Rio Grande riverside in 1991, 1998, 2001, 2006, 2009 and 2014. Trees included all alive individuals with diameter at breast height (DBH) ≥ 15.7 cm. Rates describing the dynamics of different habitats within the tree community were calculated in terms of individuals and basal area. Additionally, community structure descriptors were also included. The results suggest that the forest vegetation gradient is associated with distinct habitats within the topographic clusters as significant differences have been found in richness and diversity in addition to dynamics rates. With the highest richness and diversity in the slope sectors, the highest rates of dynamics occurred in the alluvial sectors. Therefore, processes related to the forest structural dynamics take place in accordance with environmental characteristics along the vegetation and topographic gradient.