Abstract
ABSTRACT Climatic conditions stimulates the cambial activity of plants, and cause significant changes in trunk diameter growth and wood characteristics. The objective of this study was to evaluate the influence of climate variables in the diameter growth rate of the stem and the wood density of Eucalyptus grandis trees in different classes of the basal area. A total of 25 Eucalyptus trees at 22 months of age were selected according to the basal area distribution. Dendrometer bands were installed at the height of 1.30 meters (DBH) to monitor the diameter growth every 14 days, for 26 months. After measuring growth, the trees were felled and wood discs were removed at the DBH level to determine the radial density profile through x-ray microdensitometry and then re-scale the average values every 14 days. Climatic variables for the monitoring period were obtained and grouped every 14 days. The effect of the climate variables was determined by maximum and minimum growth periods in assessing trunk growth. These growth periods were related with precipitation, average temperature and relative air humidity. The re-scaled wood density values, calculated using the radial growth of the tree trunks measured accurately with steel dendrometers, enabled the determination of the relationship of small changes in wood density and the effect of the climatic variations and growth rate of eucalyptus tree trunks. A high sensitivity of the wood density to variation in precipitation levels was found.
Highlights
Evaluating and monitoring the productivity of forest stands is key to understand the individual reaction of trees to stimuli and changes in climatic conditions
The results show a greater difference in current DBH increment in the tree trunk for the five basal area classes in the periods of greatest growth rates
The trunk growth rate in the level of the DBH of E. grandis trees was (i) greater in larger trees when compared to the trees in the remaining basal area classes, and (ii) affected by seasonality, mainly precipitation, average temperature and relative air humidity, with maximum and minimum increment periods
Summary
Evaluating and monitoring the productivity of forest stands is key to understand the individual reaction of trees to stimuli and changes in climatic conditions. The use of permanent dendrometers has proven to be an effective option in the continuous measurement of the growth in trunk diameter of tropical and temperate forest trees. Dendrometers enable assessing small changes in growth in reduced time intervals, and have high precision and low cost. Several studies have used dendrometers to evaluate the growth rate and pace of the trunks of tropical and temperate trees since the 1970s (MARIAUX, 1970; DÉTIENNE et al, 1989; BOTOSSO; TOMAZELLO FILHO, 2001). The study carried out by Sette Jr et al (2010) with Eucalyptus grandis is highlighted, showing the seasonal diameter growth of tree trunks as a result of the periodic cambial activity caused by climatic stimuli
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