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Understanding how climate affects tree growth is crucial for assessing climate change impacts on forests. Furthermore, trees in more competitive environments appear to respond to climate differently than trees in less competitive environments. An important tool for investigating the growth-environment relationships is tree ring dating. This study aimed to characterize the climatic factors that affect Pinus taeda growth in southern Brazil in two distinct stand types: open growth trees and competing trees. We hypothesized that competing trees present more vulnerable responses to climate variability than open growth trees. Thus, we used increment borers to access long-term growth through tree rings. Pearson’s correlation was applied to compare radial growth with monthly and annual climatic data. The chronologies generated for the two environments present similar year-to-year growth patterns. However, competing trees are more sensitive under limiting climate conditions than open growth trees. Water availability during the current spring/summer was the primary climate constraint for P. taeda growth in the region, followed by high temperatures during the summer, probably due to photosynthetic restrictions. The paper provides additional information on climatic factors that contribute to growth models and reports an important research field, considering planning forest management in the future. [ABSTRACT FROM AUTHOR]

The growth of individual trees can be simulated by multiplying a function that describes the potential by another modifier, the "modifying-potential". Modeling of the potential function for trees growing without competition determines the limit of optimum growth to species, while a modifying function sets the decrease component taking in consideration the influence of environmental factors. Thus, the aim of the study was to adjust the modifier function to describe the periodic increment in the basal area of Araucaria angustifolia trees in sites with Araucaria Forest in southern Brazil. For this, we sampled 397 individual trees. Dendrometric and morphometric variables, competition indices and increment in diameter with the chronology of widths of the growth ring were measured. Periodic increment in basal area was described by a logarithmic function that explained 57% of variance and correlated with the diameter at the beginning of the period, height, variable of crown size and competition indices. Results indicate that the modifier function can be used accurately to explain changes in growth and spatial and temporal structure of the species in the Araucaria Forest. El crecimiento de los árboles individuales se puede simular multiplicando una función que describe su potencial por otra modificadora "potencial-modificadora". El modelado de la función potencial para árboles creciendo sin competencia determina el límite de crecimiento óptimo para una especie, mientras que la función modificadora establece el componente de descenso teniendo en cuenta la influencia de factores ambientales. Así, el objetivo del estudio fue ajustar la función modificadora para describir el incremento periódico en el área basal de árboles de Araucaria angustifolia en sitios de bosques con araucaria en el sur de Brasil. Para eso, se tomaron muestras de 397 árboles individuales y se midieron sus variables dendrométricas, morfométricas, sus índices de competencia y su incremento en diámetro con la cronología de los anchos de anillos de crecimiento. El incremento periódico en el área basal fue descripto por una función logarítmica que explicó el 57% de la varianza y se correlaciona con el diámetro al inicio del periodo, altura, variable de dimensión de la copa y el índice de la competencia. Los resultados indican que se puede utilizar la función modificadora con precisión para explicar los cambios en el crecimiento, en la estructura espacial y temporal de la especie en el bosque de araucaria. [ABSTRACT FROM AUTHOR]

Operational research (OR) is a powerful tool for decision-making in optimizing forestry production planning. Thus, the objective of this study is to use the OR to solve forest regulation problems in a natural forest of Araucaria angustifolia (Bertol) Kuntze. The proposal for better management regime for the forest consisted in the elaboration of two OR problems using integer linear programming (ILP). I - the first aiming to maximize income for each regime; and the II - second aiming to define the best management alternative for three values of the De Liocourt q quotient of 1.1; 1.3 and 1.5, residual basal areas of 10.0, 12.0 and 14.0 m².ha-1 and cutting cycles of 20, 25 and 30 years, creating thus 27 management scenarios. Despite the application of cutting cycles of 20, 25 and 30 years, the management alternative that best uses the resources and maximizes the income for this area of 84 ha, in the municipality of Lages, SC, is "q" = 1.3 with residual basal area of 12 m².ha-1 for all cutting cycles. The removal of these trees in the forest will contribute to the maintenance of a future diametric structure, natural regeneration, species conservation and tree increment rate, as well as the maintenance of resources of the forest ecosystem. [ABSTRACT FROM AUTHOR]