Adaptability and Developing Potential of Pinus sylvestris var. mongolica in Gansu Arid Area

The results of studying the adaptability of \%Pinus sylvestris \%var.\%mongolica\% in Gansu arid area show that drought resistance of \%Pinus sylvestris\% is stronger than local shelter belt tree species\_\%Populus gansuensis, Elaeagnus angustifolia, \%and also stronger than local evergreen tree species\_\%Platycladus orientalis \% L Franco, \%Picea crassifolia\% Kom., \%Pinus tabulaeformis\% Carr, and \%Juniperus formosana\% Hayata. Its survival rate and annual height growth is limited by local climate and natural geographic condition. Generally, in order to improve its survival rate of seedling afforestation, its root soil would be ball enough when seedlings are transplanted; and its annual height growth increases obviously after seedlings were transplanted for 5~6 years. In comparison, the growth of \%Pinus sylvestris\% is much better than the other 4 evrgreen tree species and the superiority is obvious with the area drought development. The growth of \%Pinus sylvestris \% in introduction areas\_Hexi, Zhanggutai and original production area\_Honghuaerji shows ZhanggutaiHexiHonghuaerji; the climatic drought in Gansu arid area is the key limited factor of its growth compared with Zhanggutai. \%Pinus sylvestris \%likes sunlight, it can grow in temperature range of \{-40℃\}~50℃; sunlight and heat resources are richer in Gansu arid area, it is beneficial to \%Pinus sylvestris\%s growth and development. The growth of \%Pinus sylvestris \% is influenced by different soil types and water conditions; afforestation on leveled sand soil (pH8\^3) in irrigation condition(pH8\^0) or underground water supplying has a better survival rate and growth. Most irrigation water quality and soil condition in Gansu arid area is favored for the growth. \%Pinus sylretris\% is also a better afforesting tree species of wind break and sand fixation viewed from stronger disease and worm resistance, bigger developing potential, so it should be developed in Gansu arid area.