Abstract: The aims of this work were to quantify total aboveground biomass and organic carbon in native trees of Araucaria angustifolia (Bertol.) Kuntze. and to evaluate aspects related to biomass modeling, in addition to comparing the estimates of total aboveground biomass obtained by different methodologies. The work was carried out in a fragment of Mixed Ombrophilous Forest located in Fernandes Pinheiro, Paraná. The aboveground biomass was quantified by the direct method, by sampling 29 trees with DBH ? 40 cm. Traditional models of the literature that have as independent variables the diameter and height or a variation of these were adjusted. To evaluate the effects of the morphometric and qualitative variables and the age of the trees in the modeling, equations were developed by the stepwise procedure. The biomass modeling was performed by two different techniques, (i) independent adjustment, which does not consider the additivity principle; (ii) simultaneous adjustment, which considers the additivity principle. The aboveground biomass estimates obtained by three different approaches were evaluated: (i) systems of traditional equations obtained by the stepwise procedure; (ii) biomass expansion factors, considering different approaches to obtain the variable biomass of the stem and (iii) biomass expansion and conversion factors, considering different approaches to obtain the variable stem volume. The average individual production of aboveground biomass and organic carbon was 2126.5 kg.ind-1 and 935.8 kg.ind-1, respectively. The traditional and stepwise models presented satisfactory adjustment statistics to the study data. The simultaneous approach did not result in significant changes in the equation adjustment statistics when compared to the independent approach, but has the advantage of additivity, lower confidence intervals of the coefficients and, consequently, more efficient estimators, being this the most appropriate approach for estimating of the total biomass and its components. In relation to the different methodologies evaluated to estimate aboveground biomass, the approaches that consider the allometric equation systems presented interesting results, both from the point of view of the accuracy of the estimates and their applicability. The approach considering the variable cubed volume presented good results, however, it should be applied by associating it with the specific BCEF, and the product between the stem volume and the average density of the species should not be considered as a variable corresponding to the stem biomass. The approach corresponding to the estimate of the stem volume did not constitute a good estimator of the aboveground biomass, presenting the worst performance among the evaluated approaches. Keywords: additivity; biomass factors; independent modeling; simultaneous modeling.