The objective of this research was to compare the accuracy and the precision of estimates from basal area obtained by processes, intensities and methods of sampling with true values gotten from the census, in an ecotonal forest of 120 hectares in the northern region of Matogrosso, for eight groups of species and for individual tree species with dbh ≥ 30 centimeters. The applied processes were: random and the systematic, with a sampling intensity of 5% and 10% for 22 sizes and forms of plots ranging from 400 m to 10000 m². The average basal area per hectare was 11.08 m². The 2500 m² (125 m x 20 m) plots presented actual and sampling errors always inferior to 10% in estimating basal area for all species and for the 15 of greater importance values (VI). For the other groups the errors increase accordance to the decrease of tree density. For the species, individually, the errors varied from 28.7% (Vochysia sp.) to 250.59% (Courbaril hymenaeae), respectively, for the most and the least dense, thus showing the unfeasibility of applying traditional estimative processes to estimate specific parameters of species with low frequency by hectare (rare species).
Forest inventory; Forest census; Sampling processes; Sampling methods; Basal area
