The effect of surface fire on tree ring growth of Pinus radiata trees

Abstract

Pinus radiata trees showed significantly reduced basal area increments and increased latewood/earlywood ratios, when their stem was charred by surface fires even if no needle damage occurred. An interaction of fire damage and precipitation on growth was observed. Heat from forest fires is able to penetrate beyond the bark layer and damage or completely kill a tree’s cambium. Short-term growth reductions following surface fires have been reported for some species. However, most studies have in common that they describe a compound effect of stem and foliage damage. This study investigated the impact of surface fires on the radial growth of Pinus radiata, where only the stem of trees was charred, while no needle damage was recorded. Tree ring measurements were performed on cores obtained at breast height. Analysis of variance and tests, based on annual basal area increment values were calculated to quantify pre- and post-fire growth differences of tree ring width and latewood/earlywood ratios. The analysis revealed significant growth reductions following a surface fire on P. radiata in the year on which the fire occurred as well as in the following year. As a consequence of the fire, basal area increment and latewood/earlywood ratios were significantly reduced. An interaction of fire damage and precipitation on growth was observed. The obtained results show how fires without crown damage can affect growth and tree ring structure of P. radiata trees and indicate that stem char could be associated with a significant decrease in ring width and latewood/earlywood ratio.