Simulation of CO2 budget and ecological implications of sugi (Cryptomeria japonica) man-made forests in Japan

A compartment model, including removal of organic matter in a forest ecosystem, is developed to describe matter cycling and net CO2 flux of the ecosystem especially of managed forests. The model consists of five carbon stocks: atmosphere, foliage, woody matter, underground matter, and dead organic matter in the soil. Employing appropriate values of ecophysiological parameters in the model and simulation of man-made sugi (Cryptomeria japonica D. Don) plantation forests shows that these forests have high growth potential with a maximum total phytomass of over 750 t ha−1 in dry matter basis. When the typical pattern of thinning regime for sugi plantation forests in Japan is applied to the present model, the simulated forest biomass developments compare well with mensuration data from various forestry sites. The CO2 balance between the sugi forest ecosystem and the atmosphere reveals a net CO2 fixation of 49.38 million ton CO2 year−1 by all sugi forests of 4.509 million ha in Japan during 1986. Assuming that all the forest in Japan is to be changed to sugi plantation, the potential CO2 sequestration by the forests will be improved 40% at most. Examining the forest development with various patterns of removal shows that a fixed rate of organic matter removal has a possibility to lead to extermination of the ecosystem, whereas proportional removal never cause ecosystem death. The present model makes it possible to examine forest development in terms of matter cycling with tree removal, and has further ecological implications for forest conservation and management.