Abstract:

The Tianshan Mountains are an important source of water in Xinjiang, China. The Picea schrenkiana forest is the dominant species of Xinjiang’s mountain forests. This study takes P.schrenkiana forest as the research object,and discusses the distribution and variation of the biomass of P.schrenkiana forest in various organs (stems, branch, leaves, bark, roots) ,which will provide data support for the integrated forest management in the study area and be of great significance for the protection, restoration and development of P.schrenkiana forest of the Tianshan Mountains. A total of 78 sampling plots with a radius of 10 m were set up from the elevation of 1 500-2 800 m with P.schrenkiana（Schrenk’s spruce）forest of Tianshan Mountains, and all trees in the plots was measured. According to the established biomass estimation equations of P.schrenkiana forest, this study analyzed the distribution and variation of the biomass of P.schrenkiana forest in the Tianshan Mountains. The results show as follows: (1) The mean value of biomass of P.schrenkiana forest in the study area was 388.74 t·hm^-2, and the stems, branches, roots, leaves and bark accounted for 43.65%,28.60%,13.49%,11.08% and 3.18% of the biomass, respectively. The proportion of stems is the largest, and the proportion of bark is the smallest; the percentage of biomass in each diameter class is:33.53% (40-50 cm),20.13% (20-30 cm),19.59% (30-40 cm),18.19% (50-60 cm) and 2.05% (10-20 cm);the proportion of tree biomass in different tree height scales is forming a descending order list as follows:48.78% for the height range from 20m to 30 m,35.27% for the height range from 10 m to 20 m, 14.70%  for the height range from 30 m to 40 m and 1.25% for the height range from 0 m to 10 m; the distribution percentage of aboveground biomass and belowground biomass is: 87.54% (340.30 t·hm^-2) and 12.46% (48.44 t·hm^-2), respectively. (2) There was a hump-shaped curve by which the biomass of P.schrenkiana forest reached its peak value of 611.58 t·hm^-2 at the elevation of 2 100-2 400 m. The minimum value of biomass at 1 500-1 800 m was 171.38 t·hm^-2, and the value of biomass at 1 800-2 100 m was 402.05±291.58 t·hm^-2, and the value of biomass at 2 400-2 800 m was 369.97±205.09 t·hm^-2. The proportions of stems and bark biomass were decreased along with the increase of elevation, the biomass of branches was increased gradually, and the biomass of leaves and roots was decreased first and then increased. The biomass of P.schrenkiana  with diameters being 20-30 cm,30-40 cm and 50-60 cm displayed a hump-shaped curve with the increase of elevation, and reached its peak value at the elevation of 2 100-2 400 m. The biomass of P.schrenkiana with a tree height of 10-20 m was gradually increased with the increase of elevation, and the biomass of P.schrenkiana with a tree height of 20-30 m was increased first and then decreased, reaching a maximum value at the altitude of 2 100-2 400 m. The biomass of the forest showed a decreasing trend from the west to the east in the study area. The forest density, elevation and precipitation jointly determined the size of forest biomass and its variation. The places at the elevation of 2 100-2 400 m are the most suitable places for growing P.schrenkiana forest in this study area.

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