Regeneração de espécies arbóreas em clareiras antropizadas na Reserva de Desenvolvimento Sustentável Mamirauá- RDSM, Amazônia Central

Abstract

Among the studies done about canopy gaps in tropical regions, very few analyze the patterns of regeneration in anthropic canopy gaps in the Amazon flooded forests, especially on the várzeas, the most populated rural areas of the region. This study aimed to compare the patterns of forest regeneration in the várzea after agricultural and selective logging activities, compared to natural regeneration of the intact stands. Twenty gaps originating from agricultural activities and seventeen originating from selective logging were analysed and compared to seventeen gaps in the understory forest of so-called high várzea forests (subjected to flooding by a water column of up to 3 m), located in the sector of Jarauá RDSM, Central Amazonia, Brazil. In each gap a circular plot with 5 m radius was established, and all individuals above 1 m height up to <10 cm DBH (diameter at breast height) were inventoried. The species present in gaps of agricultural origin (CA), selective logging (CE), and in the continuous canopy (SB) were determined and ranked according to the Importance Value Index (IVI). Furthermore basal area, species richness and strucutral parameters such as diameter distribution of the gaps were analysed and the floristic composition compared. Based on allometric models considering DBH, height and wood densities obtained from literature biomass of the different gaps was estimated. Was sampled a total of 1976 individuals belonging to 42 families and 177 species, 436 individuals in agricultural gaps (1570.80 m2), 885 individuals in selective logging gaps (1335.18 m2) and 655 individuals in the continuous canopy (1335, 18 m2). DBH and height of individuals differed among vegetation types CA, CE and SB. The correlation coefficient (r2) in gaps of agriculture was 72% to 436 individuals, 70% in gaps of selective logging to 855 individuals and 76% to 655 individuals in continuous canopy. Considering the average values for each vegetation type, it was observed that the biomass was higher in CA> SB> EC. In contrast to the gaps of agricultural origin, selective logging and continuous canopy gaps had a higher floristic similarity, as well as a higher diversity of regenerating species, indicating that agricultural activity has a greater impact on the forest s regeneration.