Recorrência dos incêndios e fitossociologia da vegetação em áreas com diferentes regimes de queima no Parque Nacional da Chapada Diamantina

Abstract

The occurrence of wildfires is a frequent disturbance in ecosystems, especially in savannas and grassland. In Brazil, little is known about the vegetation fire dynamics in regions such as the Chapada Diamantina, where there is a predominance of rocky fields. In this study, the recurrence of fires in the Chapada Diamantina National Park between 1985 and 2010 is described. Based on fire occurrence data, we determined sites with different burning schemes where underwent phytosociological analysis. The vegetation was divided into three components: graminoid, herbaceous and shrub-woody. Correlation tests were performed trying to determine the relationship between the coverage of these components at each site and time lapse between fires. The results showed that 59.41% of the National Park were hit by fire up to four events in the considered period, while 1.01% were achieved five to nine fire events. The habitats where wildfires were not registered included higher areas interspersed with deep river valleys at northern of Mucugê town. Other areas not affected by wildfires included seasonal forests and some "campo rupestre" areas at south and east of the town referred above. The map about the time since last burning shows the widest fire extensions in the interval that includes 2008's season (three to four years) when 41,93% of the National Park burned. The phytosociological analysis showed a low similarity between the areas. Differences in composition and coverage were related with sites phytophysiognomy and edaphic aspects. The graminoid component is the only one whose coverage was significantly correlated with the time between fires (F: 324.7204; r = 0.997, p = 0.0021). There is great variation in fire regime between different areas of the National Park, which has implications for its management. Areas where the outbreaks are less common, the direct fighting may be recommended. In areas with a higher recurrence rate, the adoption of control measures may be more effective. The coincidence observed between the recurrence of large fires and the likely occurrence of evergreen-of-Mucugê (Comanthera mucugensis (Giul.) L.R. Parra & Giul.) indicates the need for additional protective actions and research on this species and associated ecosystems.