Estrutura, dinâmica e expansão de um gradiente florestal ao longo de 15 anos de monitoramento

Abstract

(Structure, dynamics and expansion of a forest gradient over 15 years of monitoring). The study of dynamics in rain forests is extremely important for the understanding of its high diversity and its conservation, thus making future predictions of a forest community. Cluster the phylogenetically different species in groups with similar traits, helps in understanding the complex structure of rain forests. The aim this paper was to assess the parameters of the dynamics of a forest formation made up three vegetation types, cerradão (woodland savanna), semideciduous seasonal forest and riparian forest and identify dynamic process groups (mortality and recruitment). In 2012 was taken the third measured of individuals collected in the forest continuum of RPPN Panga Ecological Reserve, Uberlândia, MG, with periodic measurements in intervals of five years. The inventory was conducted in 211 sample plots (10 x 10 m) distributed in eight parallel transects each other and perpendicular to the stream of Ribeirão Panga. The inclusion standard for the sample was of individuals with circumference at breast height (CBH) greater than or equal to 15 centimeters. We calculated phytosociological and dynamics parameters. We drew up a Euller Venn s diagram of species occurrence among phytophysiognomies for the four years of measurement. The Shannon-Wiener diversity were compared by Hutcheson t-test between the first T0 (1997) and fourth T3 (2012) inventory for forest gradient and its phytophysiognomies. We tested the similarity between vegetation types for four years inventoried and we grouped the most representative species (n ≥ 10 tree the at least one year inventoried) in dynamics process groups (mortality and recruitment). Mortality rates between the years 2007-2012 were 2,28, 2,34, 2,52 and 2,64 %.year-1 and recruitment rates were 2,47, 2,60, 2,29 and 3,29 %.year-1, respectively for the forest gradient, woodland savanna, semideciduous seasonal forest and riparian forest. An evident decrease occurred in the number of species exclusive occurrence in woodland savanna. There was a significant difference in Shannon-Wiener diversity in the woodland savanna (t = 2,229; p = 0,0259) and semideciduous seasonal forest (t = -2,102; p = 0,0356). We evidenced increase of floristic similarity among vegetation types over the years. In woodland savanna, the group G2 ( ↓ M ↑ R) comprised mostly in shade-tolerant and non-pioneer species and G3 ( ↑ M ↓ R) by species typical of cerrado sensu stricto and edges of forest fragments. Already in semideciduous seasonal forest, the group G2 was composed of non-pioneer species, canopy and understory and G3 by pioneer species. The group G4 ( ↑ M ↑ R) was absent in the riparian forest. The forest gradient is found in a good state of preservation. Woodland savanna is being construction, semideciduous seasonal forest is in a process of self-thinning and riparian forest go through oscillations in its dynamics rates. With the changes in the rates of similarity, diversity of species and groups formed by dynamic processes, we can show significant changes within the forest gradient with the expansion of semideciduous forest.