Abstract The aim of this study was to quantify the aboveground biomass and organic carbon of Araucaria angustifolia (Bertol.) Kuntze in a Mixed Ombrophilous Montane Forest in the state of Paraná. The aboveground biomass determination was carried out according to the direct method, using 29 trees with Diameter at Breast Height (DBH) ≥ 40 cm. The trees were felled, cubed and weighed by compartments, which were sampled for determining moisture and carbon content. The average aerial biomass and carbon were 2,126.5 kg ind-1 and 935.8 kg ind-1, respectively. The moisture content resulted in a mean individual accumulation of 2,376.6 liters ind-1 of water. Age did not necessarily result in higher volume production but resulted in higher stem biomass production. Organic carbon accumulation by native A. angustifolia trees should support carbon credits as an incentive for the conservation of araucaria and Mixed Ombrophilous Forest fragments.

ABSTRACT The aims of the present study were to test the hypothesis that data stratification by cluster analysis and the use of other variables, in addition to DBH, can improve the precision of the estimates in diametric increment modeling for Mixed Ombrophilous Forest species. The study was carried out in the Irati National Forest. Data from 25 permanent sample plots of 1 ha each were used with all individuals presenting DBH equal to or greater than 10 cm being identified and measured. The increment modeling was performed for the whole forest (non-stratified data), ecological groups and species subgroups (stratified data) defined by cluster analysis. DBH presented a low correlation with the diametric increment and the use of other independent variables had a positive effect on the fitting, reducing the standard error of estimate and increasing the coefficient of determination. The data stratification did not make the models suitable to estimate the diametric increment; however, it provided improvements by reducing the standard error of estimate, suggesting that this technique can be better applied in the search for improvements to diametric modeling in natural forests.

RESUMO Este estudo teve por objetivo determinar o estoque de madeira por amostragem sistemática e pelas tecnologias de geoinformação a fim de elaborar mapas de produtividade florestal, como forma de pós-estratificação do inventário florestal. Foram alocadas 24 parcelas de 625 m2 posicionadas a cada 70 m de distância. O mapa de produtividade foi gerado após seleção de um modelo para ajuste do semivariograma entre os volumes das parcelas. Estimou-se um volume total de 3.753,9 m3 com o inventário florestal por amostragem sistemática, enquanto com o mapa de produtividade elaborado com técnicas de silvicultura de precisão determinou-se um volume total de 3.768,9 m3. A análise de variância comprovou que existe diferença significativa entre as médias dos estratos e a partir desta constatação as estimativas foram geradas por estrato, estimando-se então, um volume total de 3.772,9 m3. A técnica de silvicultura de precisão mostrou ser uma ferramenta eficiente na pós-estratificação de inventários florestais.

ABSTRACT This study aimed to determine the wood stock through systematic sampling and geoinformation technologies in order to elaborate maps of forest productivity as a forest post-stratification inventory. We positioned 24 plots of 625 m2 each ina distance of 70 m from each other. The yield map was generated after selecting a model for semivariogram adjustment between volumes in the plots. A 3,753.9 m3 total volume was estimated in the forest inventory through systematic sampling, while the yield map produced with precision forestry techniques showed a total volume of 3,768.9 m3. The analysis of variance showed that there is a significant difference between the means of the strata and based on this fact, the estimates were generated per stratum, then the total volume of 3,772.9 m3 was estimated. The precision forestry technique proved to be an efficient tool in the post-stratification of forest inventories.