Abstract:

The biomass and distribution of Populus×xiaohei plantation with different stand densities and ages were studied by the methods of sampling permanent plot and allometric dimension analysis in sand land of North China. The biomass of plantation with densities of 1 000,500 and 250 tree5hm^-2 was measured by the model of W=aD^b. The biomass of 27 years old P.×xiaohei plantations was 85.23,102.60 and 86.74 t·hm^-2 ,respectively; While the biomass of 29 years old P.×xiaohei plantations was 88.64,104.90 and 90.94 t·hm^-2 ,respectively. Stand biomass had a close correlation with the stand density and the age. It first increased then reduced along with the increase of stand density, but increased along with the increase of stand age. Stand density had the important influence to the biomass distribution of the P.×xiaohei organs. The stand density different, the proportion of the organ biomass was different. The proportion of leaf and bark biomass increased along with the increase of stand density, but the proportion of stem, branch and root biomass did not display the obvious regularity along with the increase of stand density. In the three densities of plantations, the proportion of stem biomass was the most, the leaf the least. The biomass distribution of three densities of plantations assumed the normal probability distribution.In plantation with density of 1 000 tree·hm^-2, 72.37 per cent of biomass centralized on diameter classes from 18 to 22 cm. 90.02 per cent of biomass centralized on classes from 20 to 26 cm in plantations with density of 500 tree·hm^-2; In plantation with density of 250 tree·hm^-2, 68.27 per cent of biomass centralized on classes from 26 to 30 cm.

Key words: biomass, distribution patterns, density, stand age, Populus×, xiaohei, sandy land of North China