Banca de QUALIFICAÇÃO: KESID RAFAEL CAVALCANTE PAIXÃO

Floristics of secondary forest formations in Rondônia.

Degraded area, Amazon, soil, Rondônia, floristics

Deforestation in the Amazon intensified from the 1970s onwards when government incentives influenced the occupation of the Amazon. As a negative consequence of economic cycles in Rondônia, the native forest has been intensely exploited over the years. Since the 1980s, the state has deforested more than 66,100 km² of native forest, which corresponds to 28% of its territory. It is common in the Amazon region for areas that gradually lost their natural fertility to stop being economically exploited and, over time, to observe the growth of secondary forests. These forests are related to the maintenance of biodiversity, and play a role in mitigating the impacts generated by deforestation. Secondary forests in the Amazon are home to 56.6% of all secondary forest in the country. Due to their importance in preserving the environment, knowing them represents an important step in our strategies to mitigate the damage caused by deforestation. The objective was to describe the diversity of secondary forests in a portion of the territory of Rondônia and to understand the occurrence and relationship of arboreal flora in secondary formations with soil attributes in degraded areas. This work is organized into two chapters. In the first, we approach the flora of plantations and secondary forest formations, describing their composition and ecological characteristics. The information used was obtained from bibliographies and from information contained in botanical collection forms carried out in Rondônia, for the species considered. A total of 49 species from 42 genera and 23 families made up the list. Of the total species, 52% are pioneers, 46% are secondary and 2% are climax species. For the planting group, 51% are diversity and 31% are cover. In the second chapter, the influence of soil attributes on the phytosociological structure of three areas of secondary forest located in the Rio Preto-Jacundá State Extractive Reserve was studied. For the floristic and phytosociological studies, 22 plots of 10 m x 100 m were implanted randomly. As an inclusion criterion, DBH ≥ 5 cm was used. The soil was approached from composite sampling obtained inside each of the plots at three different depths: 0-10 cm, 10-20 cm and 20-40cm. 2818 individuals were sampled, distributed in 172 species, 115 genera and 44 families and with an unidentified taxon. The Shannon-Weaner (H') specific diversity index was 3.44 nats.indˉ¹. The Pielou evenness index was 0.82. At sampling, all plots showed low to very low pH (3.9 to 5.4). Phosphorus (P) and Magnesium showed very low levels in all plots. Potassium (K), Calcium (Ca) and Magnesium (Mg) showed low levels in all plots and depths.