島根大学松江試験地に植栽されたヒノキアスナロ人工林の成長予測

In the Matsue Forest, a plantation of hiba arborvitae was established in 1970. Since 1995, we have conducted tree census periodically at that plantation. Based on the census data we looked back the growth history of the planted trees and try to forecast their future growth. A D-H curve plotted with the data of 2014 census indicated that maximum tree height could be 34 m, while that curve made from the data of 1995 exhibited the maximum value of 15 m. Current annual increment of basal area and stand volume has been significantly improved during past two decades to show the maximum values, 1.77 m^2 ha^<-1> year^<-1> and 14.5 m^3 ha^<-1> year^<-1>, respectively. As a result of calculation, this plantation would reach the maximum stand volume 384 m^3 ha^<-1>. At the age of 72, the stand volume of the plantation might exceed 380 m^3 ha^<-1> and relative growth rate would be close to 0 year^<-1>. This means no drastic growth could be expected after that age. From the viewpoint of timber production, we need to decide how to manage this plantation around 70th year after establishment, e.g., to clear-cut the whole stand or to select timbers for logging. However, we need some more time to evaluate the behavior of hiba arborvitae plantation accurately.