Inventário florestal contínuo na Floresta Estadual do Amapá : dinâmica de espécies arbóreas e dimensão da unidade amostral

Abstract

The approach of this study was focused on the dynamic and dimension of sample units for continuous forest inventory in a dense ombrophilous rain forest, located in the conservation unit of sustainable use called State of Amapá Forest, in the city of Porto Grande. In the area, there were established five permanent plots of 100 m x 100 m (1ha) each, established in accordance with the criteria of the monitoring network of the dynamics of Amazon forests, with level of inclusion of trees covering DBH≥ 10 cm. The evaluations were carried out in two occasions, 2010 and 2016. It was calculated the periodic annual increment (PAI) in diameter, basal area and volume, as well as the increase in volume per species and by the Logging Value Group (LVG) and the rates of entry and mortality. In addition, it was evaluated the dimension (area and shape) of sampling unit ideal for use in continuous inventories in the Amazon forests, evaluating its accuracy and efficiency in the estimation of quantitative parameters evaluated (PAI in diameter, basal area and volume and also basal area and volume just for the year 2016). There were simulated five dimensions of plots ranging from 400 m2 to 1600 m2 allocated randomly inside the permanent plots. There were measured the time of installation and measurement of the plots, from the first to the last tree. The average values for mortality and admission rates found in the period 2010-2016 were 1.47% and 0.93%. The periodic annual increments in diameter, basal area and volume were respectively: 0,24 cm-1; 0,45 m2.ha-1; 4.70 m3.ha-1. Among the species that obtained the largest increases in volume are Eschweilera sp, Inga auristellae, Iryanthera paraenses, Theobroma subincanum and Tachigali myrmecophila. The dimensions tested were analyzed for their accuracy and method relative efficiency in estimating growth and stock variables. The dimensions that presented the greatest relative efficiency were the units of 20 m x 20 m (400 m2) and 40 x 40 m (1600 m2). The forest under study presented a negative balance in the analyzed period, however it presented an increase in the growth variables and indicated the volumetric potential for management purposes. The dimensions indicated for continuous forest inventory in the region, depending on the purpose of the inventory, as those with high quantitative rigor for the stock variables, the standard plot with 100 m x 100 m is recommended. Already for the monitoring of growth variables, plots of 20 m x 20 m are effective and recommended.