Changes of arbor layer aboveground biomass of Pinus spp. and Quercus spp. mixed forests along altitudinal gradient on the southern slope of Qinling Mountains, northwestern China.

In this research, the data from field survey and allometric models summarized by other experts were combined to analyze the changing rules of forest structure and biomass along altitudinal gradient. The results revealed that aboveground biomass showed a decreasing trend with the increase of altitude gradient. Simultaneously, the biomass proportion of Pinaceae increased with no significant difference. Forests at each altitude were destroyed in different degrees by natural or anthropogenic disturbance, especially under the elevation of 1 100 m. In general, biomass was negatively related to interference factors (r=－0.698, P0.01). Compared with other neighboring regions, the biomass of Pinus spp. and Quercus spp. forest was relatively lower in this region. So this research suggests that reasonable management strategy should be made to meet the optimal development.