Long-term growth analyses of Japanese cedar trees in a plantation: neighborhood competition and persistence of initial growth deviations

Abstract

The individual growth of tree diameter at breast height (dbh) is analyzed in an even-aged plantation of Cryptomeria japonica from stand age of 45 to 94 years, to examine how the growth of individual trees has been affected by the changes in spacing resulting from thinning operations. At any age, a significant proportion (0.37-0.46) of the variation in dbh growth during a 5-11-year period was explained by dbh at the beginning of the period, probably due to greater leaf mass of larger trees. Next, either one-sided or two-sided competition was added to the model, by calculating the basal area (BA) of neighboring trees around each tree within a given radius or BA for trees having larger dbh than the focal tree within the radius. After preliminary analyses, a radius of 8 m was selected as the critical range for tree competition. Although both types of competition explained a significant proportion (0.09-0.43) of growth variation, one-sided competition was not significant at ages greater than 54 years. Based on the model at 45 years of age, the initial deviation of growth rate for each tree from the predicted rate was calculated and added to the models as a third variable. This raised the coefficient of determination up to 0.50-0.74. These findings have practical significance for forest plantation management, particularly for controlling the growth of standing trees via thinning, to produce high-quality timber in the future.

Effects of thinning and site productivity on culmination of stand growth: results from long-term monitoring experiments in Japanese cedar (Cryptomeria japonica D. Don) forests in northeastern Japan

“…Osumi et al (2000) and Nishizono et al (2008) also reported that the mean annual volume increment curve was relatively flat near and beyond culmination. In addition, several studies have reported that old-aged Japanese cedar trees were able to respond to increased resource availability following reduction in stand density by thinning (Kunisaki et al 1999;Osumi et al 2000;Masaki et al 2006;Nishizono et al 2006;Sawata et al 2007). Apparently, thinning is effective among old-aged Japanese cedar trees.…”

“…Recognition of this fact has led to some recent studies on growth of stands and individual trees in old-aged Japanese cedar forests (e.g., Kunisaki et al 1999;Osumi et al 2000;Masaki et al 2006;Nishizono et al 2006Nishizono et al , 2008Sawata et al 2007). Osumi et al (2000) and Nishizono et al (2008) reported that stands in the Akita District of northeastern Japan seldom reached culmination of mean annual volume increment until they were 60-years old.…”

Effects of topography and planted trees on the distribution of naturally regenerated broad-leaved trees in a 140-year-oldCryptomeria japonicaplantation in northern Kyushu, Japan

“…Several studies have examined neighborhood competition, and suggested approximately 10 m might be the critical range to be affected by neighboring trees (e.g., Nishimura et al 2003;Masaki et al 2006). In this study, we therefore examined the effects of planted trees on naturally regenerated broad-leaved trees and the effects of canopy trees on subcanopy trees for broad-leaved species simultaneously in a 10 9 10 m cell unit.…”

Review of Plant Species Diversity in Managed Forests in Japan

“…In Japan, long-rotation management is becoming increasingly widespread as it results in the production of larger and more valuable timber and is a way of hedging against fluctuations in the price of timber [37,38]. Long-rotation plantations have been observed to maintain and increase species diversity and develop stand structure better than standard-rotation plantations [39,40].…”