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The aim of this study was to assess and model the evolution of the hypsometric relationship in Araucaria angustifolia plantations grown in the 1940's and 1960's in the Irati National Forest, in the mid-south region of Paraná state, Brazil. Using the complete stem analysis method, it was possible to reconstitute the past annual growth of the diameter at 1.3 m (d) and of the total height (h) of a sample of 30 trees, selected so as to cover diametric and age variability. Eleven discs were removed from each tree at 0.1 and 1.3 m and at 15, 25, 35,..., 95% of the total height. Eleven models traditionally used in hypsometric relationships were tested, two of which were considered generic because they involved the age variable. The models were selected based on the Adjusted Coefficient of Determination (R²Adj), Standard Estimate Error (Syx), absolute (m) and relative (%), and on the graphic distribution of residues in percentage. In the models tested by age, no tendencies were observed and erros (Syx) remained below 14.6%, except for ages 5 and 11. However, the coefficients of determination were low, ranging from 0.29 to 0.55. The Curtis generic model (1970), selected to represent the h/d curve for all ages, also presented a satisfactory performance (R²Adj = 0.87 and Syx = 16%), with results similar to those obtained for the models in each age. As age increases, the h/d curve shifts to the right and changes level, remaining steep at the younger ages and more stable and flat as the population nears the end of its cycle. Nesta pesquisa, objetivou-se avaliar e modelar a evolução da relação hipsométrica em plantios de Araucaria angustifolia, estabelecidos nas décadas de 40 a 60 na Floresta Nacional de Irati, região Centro-Sul do Paraná. Com o método de análise de tronco completa foi feita a reconstituição do crescimento anual passado do diâmetro a 1,3m do solo (d) e da altura total (h) de uma amostra com 30 árvores, selecionadas de forma a cobrir a variabilidade diamétrica e de idade. De cada árvore, foram retirados 11 discos nas alturas 0,1 e 1,3 m e nas alturas de 15, 25, 35,..., 95% da altura total. Foram testados 11 modelos tradicionalmente usados para relações hipsométricas, sendo dois deles denominados de genéricos, porque envolvem a variável idade. Os modelos foram selecionados com base no Coeficiente de Determinação Ajustado (R²Adj), Erro Padrão de Estimativa (Syx) absoluto (m) e relativo (%) e na distribuição gráfica dos resíduos em percentagem. Os modelos testados por idade se mostraram sem tendências, com erros (Syx ) inferiores a 14,6%, exceto para as idades 5 e 11 anos, no entanto, os coeficientes de determinação foram baixos, variando de 0,29 a 0,55. O modelo genérico de Curtis (1970), selecionado para representar a curva h/d em todas as idades, também apresentou um bom desempenho (R²Adj = 0,87 e Syx = 16%) e com resultados similares àqueles obtidos com os modelos em cada idade. Com o avanço da idade, a curva h/d se desloca para a direita e muda de patamar, sendo íngreme nas idades mais jovens, tornando-se mais estável e aplainada quando o povoamento tende para o final de seu ciclo.

The aim of this study was to assess and model the evolution of the hypsometric relationship in Araucaria angustifoliaplantations grown in the 1940’s and 1960’s in the Irati National Forest, in the mid-south region of Paraná state, Brazil. Using thecomplete stem analysis method, it was possible to reconstitute the past annual growth of the diameter at 1.3 m (d) and of the totalheight (h) of a sample of 30 trees, selected so as to cover diametric and age variability. Eleven discs were removed from each tree at0.1 and 1.3 m and at 15, 25, 35,..., 95% of the total height. Eleven models traditionally used in hypsometric relationships were tested,two of which were considered generic because they involved the age variable. The models were selected based on the AdjustedCoefficient of Determination (R²Adj), Standard Estimate Error (Syx), absolute (m) and relative (%), and on the graphic distribution ofresidues in percentage. In the models tested by age, no tendencies were observed and erros (Syx) remained below 14.6%, except for ages5 and 11. However, the coefficients of determination were low, ranging from 0.29 to 0.55. The Curtis generic model (1970), selectedto represent the h/d curve for all ages, also presented a satisfactory performance (R²Adj = 0.87 and Syx = 16%), with results similar tothose obtained for the models in each age. As age increases, the h/d curve shifts to the right and changes level, remaining steep at theyounger ages and more stable and flat as the population nears the end of its cycle.