Abstract:A systematic study on dynamics of individual dry weight increment, net mean productivity, stand biomass and primary productivity of alder and cypress artificial mixed forest has been carried out in Yanting county, Sichuan province. The study on the biomass of stands at different ages shows that the biomass accumulation of different organisms at stand age and the proportion of trunk increased while those of leaf, branch and root system weight decreased. The average net productivity of alder tree increased from 2 and 12 years old and reached the peak in the period between the 12th to 14th year and then decreased gradually after the 16th year. The same tendency was presented in the alder biomass structure and in its vertical distribution. These indicate that the quantitative maturity of alder occurred as it was 18 years old in the mixed forests. The accumulation of cypress leaf showed a so-called "advanced phenomenon‘. The net primary productivity of the cypress trees fitted "J" type of curve. The biomass structure and its vertical distribution were still in the state of dramatic differentiation in the duration between the 2nd and 18th year of plant growth. Among a few types of subtropical artificial forests, the biomass and net primary productivity of the alder and cypress mixed forest is the relatively high. Therefore, this kind of artificial forest may have integrated ecological and economic benefits.