Diameter Growth in Mixed-Age Plantation of Araucaria angustifolia

Abstract

This study aims to evaluate the diameter growth of a mixed-aged plantation of Araucaria angustifolia (Bertol.) Kuntze (Brazilian pine), located in the municipality of Ivaí, Paraná, through partial stem analysis using increment cores. The study stand covers approximately 41.5 hectares and is managed under a multi-strata system, where the canopy is composed of Araucaria angustifolia intercropped with a commercial plantation of Ilex paraguariensis St. Hil. (yerba mate). For the analyses, 30 trees were selected, from which two increment cores were collected using a Pressler borer. These cores were later processed and digitized to allow for measurement of the growth rings. Based on the compiled data, growth and yield functions by Chapman-Richards (C-R) and Schumacher (SCH) were fitted to assess growth trends over time, using the Current Annual Increment (CAI) as a reference. The average CAI was then correlated with meteorological variables, including temperature, precipitation, and hours of sunlight. The Araucaria angustifolia stand showed ages ranging from 25 to 50 years, with an average diameter of 38.5 cm. The Chapman-Richards model provided the best fit to the dataset, allowing for the technical cutting age to be estimated at 14 years, when average diameters of 24.4 cm could be obtained. It was found that diameter growth over time was not correlated with local climate data.