Age-related changes in stand volume growth of cryptomeria japonica plantations in akita district, Northeastern Japan

We analyzed long-term monitoring data on old-aged plantations of sugi (Cryptomeria japonica) in Akita District to examine age-related changes in stand volume growth. Mean annual net volume increment increased with increasing age, and then decreased after an age of 80-90 years, or sustained a constant level. The culmination age of mean annual gross volume increment was greater than that of the mean annual net volume increment. Mean annual increment in dominant tree height peaked before the first recorded measurement (plantation age 27-39 years), and decreased with increasing age. Mean annual net increment in stand basal area increased with increasing age, and then decreased after an age of 40-80 years. Our results suggest that sugi stands in Akita District seldom reach the culmination of mean annual volume increment until an age of 60 years, regardless of site productivity and stand density management; a thinning regime may extend the culmination age by reducing mortality due to suppression and disturbance. Additionally, dominant tree height growth peaks early, followed by basal area growth and stand volume growth.