Abstract: The dynamics of aboveground biomass and stem volume in subalpine coniferous Picea asperata plantations with different stand ages in 70 years of artificial restoration process were studied by adopting the concept of space as a substitute for time.The results indicated that before 20 years of stand age,the biomass of spruce single tree grew quite slow,with that of the twigs and needles accounting for about 50%;after 20 years,it increased obviously,with 60% of biomass accumulated in stem;from 30 to 40 years,the increasing rate of biomass relatively slowed down,and maintained a rapid growth after 40 years.The biomass of spruce population showed a similar trend,though the period of relative slow-down of growth continued from 30 to 50 years.For the biomass of community as a whole,it presented a general continuous increase,but varied greatly for different layers.In shrub layer,the biomass rose rapidly at the early stage of plantation establishment and gradually decreased after 20 years,while that of the herbaceous plants reduced continuously and accounted less than 0.2% of the total biomass of community when the stand reached 70 years.Both the mean annual increment and the current annual increment of stem volume of spruce single tree went up with the increasing stand age,and more rapidly at the later stages.Similar changes were observed for the stock volume of the plantations,with the only difference that the current annual increment from 30 to 50 years was relatively reduced.Based on the data from stem analysis and growth ring measurement,regression models of stem volume with DBH and tree height of 70 years Picea asperata plantation were established.

Key words: Subalpine coniferous forest, Ecological process, Artificial restoration, Biomass, Stem volume, Picea asperata