Meteorological effects on 30-years-grown Pinus taeda under a gradient of crown thinning intensities in southern Brazil

Abstract

Pinus taeda plantations are an important economic activity in southern Brazil, where edaphoclimatic conditions are optimal. Understanding how meteorological conditions influence tree growth is important in such a favorable environment for reaching high growth rates and for predicting tree growth responses to climate change. The study was designed to evaluate the influence of meteorological variables on 30 years of radial growth of P. taeda trees subjected to different crown thinning intensities in southern Brazil. In total, 9280 measurements of ring width and age were evaluated. Residual chronologies were obtained according to standard dendrochronology techniques. Correlation was calculated between chronologies and meteorological variables, and thus the direction and magnitude of the relationship between meteorology and growth was addressed. Results indicated that, accounting for the whole year, meteorological conditions show no particular influence on the radial growth of Pinus taeda trees in the studied region. The exception was the vapor pressure deficit, with a significant and negative correlation with the radial growth of trees at all thinning intensities. When considering seasons, several consistent correlations were detected. Rainfall during winter, previously or at the end of the growing season, was positively correlated with the radial growth of trees at all thinning intensities. A consistent negative correlation between minimum and maximum temperature during winter and the radial growth of trees shows that P. taeda in southern Brazil, regardless of thinning intensity, benefit from colder winters in general and, particularly, from colder days during winter. Although temperature increases in the highlands of southern Brazil, as a result of global warming, may not render the cultivation of P. taeda unfeasible, they may restrict or shift the region of optimum growth as well as require changes in the genetic material. Results also suggest that high-intensity thinning may increase the influence of temperature on growth pattern of the stands.