Estoque de necromassa lenhosa e mortalidade de árvores em uma floresta secundária no nordeste paraense

Abstract

Tree mortality is an important process in forest ecosystems and is associated with stand dynamics. This forest component plays an important role in biogeochemical cycles, especially carbon cycles. Despite its importance, there are still gaps in the community and ecosystem responses to tree mortality and how the processes that generate it occur in secondary forests. In this sense, the following questions have arisen: how does the weighting of basic wood density, considering different decomposition classes, influence the estimation of necromass stock? And what can explain the death of the community's trees in this region? In order to better understand these phenomena, the study aimed to estimate the necromass stored in the woody reservoir of decomposing material, using basic wood density as an indicator, and to investigate how trees are dying in a fragment of secondary forest in the municipality of Igarapé-Açu in northeastern Pará. To achieve this objective, this work was divided into two chapters. The first chapter looked at tree necromass in a secondary forest in the Amazon and the second investigated possible explanations for the death of trees in the community and analyzed their behavior within the site. The experiment was conducted at the Fazenda Escola de Igarapé - Açu and 30 conglomerates were set up in a Maltese cross layout to measure tree individuals (branches and trees). The results obtained for the first chapter showed that statistically there was no significant difference in the estimate of necromass with the weighting of basic density; however, the data for this variable decreased as decomposition increased. The second chapter pointed out that there was no influence on the incidence of dead wood due to the modes of death and distance from the edge, but it was significant in the decomposition classes and direction of fall. In summary, the study contributes to understanding the dynamics of secondary forest stands, as tree mortality and necromass decomposition are important processes for the carbon cycle and other biogeochemical cycles. Furthermore, this study can serve as a basis for future studies.