Abstract: The study shows that the leaf area index(LAI) of mid and short rotation poplar plantations for pulp timber was increased with increasing planting density and stand age. Among the 3 poplar clones tested, NL-80351 had the highest LAI, I-72 had the lowest one and I-69 was the intermediate. The relationship between LAIand sunlight penetration rate could be described by extinction equation modified by M.Monsi and T.Saeki, and the extinction coefficient was 0.818 . LAIhad a close relationship with aboveground annual net biomass production, which could be expressed by exponential function. There existed a great difference of biomass productivity and distribution pattern among stands with different clones and planting densities at 4 years old. The biomass productivity of the stand with 1111 stems·hm^-2 was the highest, as 1.4 times as that with 500 stems·hm^-2 . NL-80351 had the highest productivity, and I-72 was the lowest. The biomass accumulation trend of stem xylem, branch xylem and bark could be described by Richards model. In different planting densities, the economic biomass for chemical pulp timber was in order of 1111>833>625>500 stem·hm^-2 at 4 years old. However, for groundwood pulp timber, it was in order of 500>625>833>1111 stems·hm^-2 . Clone NL-80351 had the highest stand economic biomass for both chemical and groundwood pulp timbers, I-72 had the lowest, and I-69 was the intermediate.

Key words: Poplar clones, Pulp timber, LAI, Net biomass productivity, Economic biomass, Quercus aliena var. acuteserrata, water, spectral reflectance, throughfall elimination, photosynthetic pigment