Dinâmica temporal na estrutura da vegetação de fragmentos florestais em Alter do Chão, PA

Abstract

Temporal changes that occurred in abundance, basal area and distribution of diametric classes are fundamental properties to understand the dynamics of a forest. These variables can provide indications about changes in vegetation structure. The objective was to characterize the structural profiles of forest fragments by examining the influence of factors such as fire and fragment size. The field research was carried out in alter do Chão's APA in 2017-2019, the data were compared with those obtained in 1998-2001 in 22 areas with permanent plots in the same region. The basal area decreased from 447.67m2/there to 313.78m2/ha, and increased the first diametric class (DBH<5 cm) from 28,950 to 39,760 ind/ha and reduction of the other classes when compared between the two times. However, total abundance increased and the number of individuals/ha in 2017-2019 was 56,656 compared with 48,790 ind/ha in 1998¬-2001. The effect of the fire was examined in the 2017-2019 data, with significant reductions among individuals with DBH smaller than 5cm and greater than 30cm in fragments with fire recording. No ratios of the vegetation structure of the current sampling (2017-2019) with the size of the fragment were found. Nor a relationship between the temporal differences of the vegetation structure with the size of the fragments between the two sampling times. Considerable net losses were observed in the basal area and a significant increase in fine trees in the long term. The results of fire fragments suggest that fires may influence the dynamics of the forest structure, although it is understood that there are other factors that can contribute to this change.