Effect of protection Against Winter Freeze Damage on Pinus sylvestris var. mongolica First-year-plantation

Pinus sylvestris var.mongolica has been successfully introduced and grownin semi arid wind sand area since 1975,however,if Pinus sylvestris var. mongolica trees afforest,most trees usually die of physiologic drought next spring,this has become the key problem in Pinus sylvestris var. mongolica silviculture.From 1996 to 1997,we studied the effect of protection against winter freeze damage on Pinus sylvestris var. mongolica first year plantation,the results showed that the survival rate of Pinus sylvestrisvar.mongolica seedlings covered with thin plastic film and soil increased by 28 5% over those covered with soil,and the cost save 921 yuan per hectare.