GABRIEL ELISEU SILVA
Abstract:
(Dynamics of the shrub-tree community of three areas of restricted sense cerrado in Jataí municipality, southwest of Goiás). The goal of this work was to verify the changes occurred in the woody community in an approximate interval of three years, associating the alterations in the vegetation structure and composition with the edaphic factors and the fire. The study was carried out in three restricted cerrado areas, using ten plots of 20 × 50m in each area, where we sampled all woody individuals with DAS (diameter at ground height) ≥ 5 cm in the first survey (T1), platelets, estimated their heights and identified their species (2009 in BAT and LAJ, and 2010 in FRP). The second survey (T2) was conducted in 2012 in the LAJ area and in 2013 in the other two areas (BAT and FRP). At T2, the survivors were remedied and those who entered the inclusion criteria (recruits) were measured and plateletized. In T1 at BAT, 70 species, 853 individuals and basal area of 8.75 m2 were found. In T2, 63 species, 601 individuals and basal area of 9.12 m2 were sampled. In the interval between the two surveys (4.16 years) nine species disappeared and two joined the community. Shannon diversity index and Pielou equability were 3.26 and 0.77, respectively, for T1. For T2, only the diversity changed, falling to 3.16. The average annual mortality rate was 11.55% and the recruitment rate 2.4%. In the JLA there were 83 species, 1391 individuals and basal area of 16.82 m2 in T1, and in T2 we sampled 87 species, 1503 individuals and basal area of 18.65 m2. Within 3.58 years, eight species entered and four disappeared into the community. The diversity index at T1 was 3.62 and at T2 3.65. The average annual mortality rate was 2.27% and the recruitment rate 4.13%. In FARP, 77 species, 1863 individuals and basal area of 10.87 m2 were found in T1, and in T2, 75 species, 1395 individuals and basal area of 10.1 m2 were sampled. Within 3.0 years, seven species disappeared and five joined the community. The diversity index at T1 was 3.62 and at T2 3.65. For equability the values were 0.8 for both surveys. The average annual mortality rate was 10.37% and the recruitment rate 1.73%. The three restricted sense cerrado fragments altered species richness, number of individuals and basal area, but there were no significant changes in diversity indices between the first and second survey. This may be related to the variation of richness, depending on the species that presented few individuals. The highest mortality rates found for BAT and FRP may be related to the presence of fire, while for LAJ the higher recruitment is associated with the absence of disturbance. The change in density and growth of individuals may still be conditioned by soil characteristics. In LAJ and BAT, the clay soil, although allowing the establishment and growth of individuals of forest and fire-sensitive species, in BAT, it is believed that fire has been acting as a limiting factor in the structure changes, preventing vegetation thickening; and in LAJ, the increase in density and increase in basal area possibly occurred due to the absence of burns. In FRP, it is suggested that eventual fire and sandy soil may contribute to limiting structural changes and community richness. Thus, in LAJ the highest recruitment rate recorded in relation to mortality may possibly be related to the absence of fire and soil characteristics, providing the tree densification and a possible successional stage of the community, indicating the formation of a cerradão. Regarding the areas of BAT and FARP, the highest mortality rates in relation to recruitment may be associated with the presence of burns, preventing the densification in the community and keeping the cerrado phytophysiognomy restricted. Key words: half-life, mortality, recruitment, doubling time, savannah vegetation, burning, soil.
