ABSTRACT Background: Litter is an important component of ecosystems, and its characteristics (e.g., production, decomposition, and nutrient and carbon content) are relevant for the ecological maintenance of different ecosystems. Previous studies on decomposition patterns have focused only on short time periods. Furthermore, there is no information regarding the actual decomposition time of organic matter in the Brazilian savanna biome known as the Cerrado. Thus, analysis of the total decomposition time can provide reliable estimates for other models. This study aimed to evaluate total litter decomposition (100%) and its relationship with seasonality and floristic composition in the savanna forest (Cerradão) formation in central Brazil. Litter bags were randomly distributed over the soil, with 10 samples collected per quarter from August 2014 to May 2020. Single- and double-entry linear regression models were used to analyze the total litter decomposition. Results: The half-life (time for which 50% of the litter was decomposed) occurred at 360 days, and 100% of litter decomposition occurred at 2070 days. The single-entry model was more satisfactory for estimating the decomposition speed. There was a positive correlation between litter decomposition and precipitation, and the floristic composition helped to explain the litter decomposition trends. Conclusion: Litter decomposition in the Cerradão is related to floristic diversity (quality of the material) and to the synergism of factors that occur mainly in the rainy season. Thus, the results of this study can contribute to conservation initiatives.

ABSTRACT This study applied a deforestation model for the entire State of Rondônia assuming three scenarios of deforestation: business as usual, optimistic and pessimistic. Those scenarios were constructed for the time-period of 2012-2050 using the Dinamica EGO software. Rondônia deforestation dataset was provided by the Agência Ambiental do Estado de Rondônia (Rondônia State Environmental Agency) and was used as input of the deforestation modeling. Based on this study results, we estimated that 32%, 37% and 47% of Rondônia’s native forest could be fully deforested by 2050 assuming the optimistic, business as usual and pessimistic scenarios, respectively. Regardless of the chosen scenario, we expect that deforestation will be spatially concentrated in Northern Rondônia in the next decades. The greatest concern, however, could be the integrity of the protected areas assuming the business as usual and/or pessimistic scenario. In addition, we expect a substantial increase of the forest fragmentation by 2050.

RESUMO A maioria dos estudos que analisa o comportamento da competição arbórea é voltada para plantios homogêneos e equiâneos. Nota-se, portanto, uma carência de informações deste tipo em florestas naturais de elevada biodiversidade. Objetivou-se com este trabalho avaliar a competição em um fragmento de Floresta Estacional Semidecidual, por grupo ecológico, grupos demandantes e não demandantes de luz para todas as espécies amostradas no fragmento. Foram empregados índices de competição independentes da distância e semidependentes da distância. O índice BAL (basal area in larger trees), sem raio de influência, obteve o melhor desempenho para analisar como a competição afeta o crescimento dos indivíduos no fragmento estudado. Concluiu-se que avaliar a competição por grupo ecológico é mais eficaz, e os resultados confirmam que a competição florestal não pode ser determinada apenas pela aplicação de um raio fixo de influência dos vizinhos em relação à árvore-objeto.

ABSTRACT Most of the studies that analyze the behavior of tree competition approach even-aged plantations. Therefore, it is possible to notice a lack of this kind of information regarding natural forests with high biodiversity. The objective of this study was to evaluate the competition in a fragment of Semi-Deciduous Seasonal Forest, according to the ecologic group, light depending and non-depending groups for all species sampled in the fragment. The Distance Independent Competition Index and Semi-Distance Independent Competition Index were applied in this study. The basal area in larger trees index, without the radius of influence, was the most efficient to analyze how the competition affects the growth of the specimens in the studied fragment. It was stated that evaluating the competition per ecologic group is more efficient. The results confirm that the forest competition cannot be determined by considering only a fixed radius of influence that embraces the neighbors and the subject tree.