Study On Afforestation Techniques Of Pinus Sylvestris Linn.Var.Mongolica Litv. In Yulin Sandy Land

Yulin sandy land ,located in north of Shaanxi province, is a part of MuUs sandy land where is rich in the mineral resource and has become the national energychemical industry base. But windyg and sandy climate as well as desertification has severly affected people's normal life and the production, and restricted regional economic development.The biological measures have been important measures to control and stabilize sand in Yulin and through many years afforestation,sand dunes have begun to move back,effective results achieved. Pinus sylvestris Linn.var.mongolica Litv. Plays an extremely vital role in this process and has become a major tree species in Yulin sandy area .But for largere scale afforestation, survival rate is quite low due to lack of good techniques, causing waste of money and labor work.A systematic research on the afforestaton techniques for Pinus sylvestris Linn.var.mongolica Litv. appears very nessessary..The research takes the sandy area of Yulin as experimental area and takes some key topics as research contents: density of tree planting and depth of root bury, favorable seaons for afforestation, afforestation test in sandy land that is stable or partially stable due to vegetation covering, selection of seedling types and influence of water loss of bare root on survival rate.Some key techniques in Pinus sylvestris Linn.var.mongolica Litv afforestation based on the determination of moisture contents, root growth as well as climatic factors are put forward, enhancing the survival rate in afforestation and achieving the economic and ecological benefits. The main results from the reaseach are: i) the depth for root burying is about 50cm for the moisture conten is highest 50cm and hairy roots are mostly concentrated in this depth below the dry layer of sand; density for afforestation is 3m×4m;ii) favorable season for afforestation is rainy seaon ( middle of August to early of September) since it cause higher survival rates;iii) vegetation covering significantly influences the effect of afforestation. Pinus sylvestris Linn.var.mongolica Litv has a highest survival rates in sandy land without vegetation covering while lowest in the land already with vegetation covered. Young stand and over-matured stand have a higher survival rate in afforestation; iv) different types of seedlings have different survival rates. Seedlings with original soil has a highest survival rate, followed in order by bagged seedlings, water-soaked seedlings, muddy-dipping seedlings and bare root seedlings; v) survival rate declines with the time of water loss for root, and survival rate can be zero. Seedlings will completely die after 40 mins'of water loss.