Research On Seedling Breeding And Forest Adaptability Of Pinus Sylvestris Var. Mongolica In Gansu Arid Desert Area

In order to make localized seedling cultivation of Pinus sylvestris var.mongolica come true,seedlings were breeded by seeds and transplants in Hexi region.And adaptability of Pinus sylvestris var.mongolica has also been researched in Gansu arid desert area.The main results are as follows.1.Seedling breeding of Pinus sylvestris var.mongolica by seeds.Dipping seeds in natural cool water to germination is optimal seed solution method.Feasible seeding quantity is 15g/m² and the depth for seeding is between 0.75cm and 1.25cm in the soil. Spring and summer are optimal seasons for seeding breeding.Flat seedbed covered with mycorrhiza soil is feasible and the soil salt content is limited.Percent of seedling emerged is the highest when powder of F_eSO₄ in soil is used of 30g/m².The optimal method for seedling safety in winter is covered by local soil after irrigation and before soil frozen. The main plant diseases and insects which harm to seedlings are damping off and small ant.2.Seedling cultivation and nursery by transplants,soil in nursery should be chosen and total salt content of soil is lower than 0.5%.Water capacity in the soil in base of membrane should be lower than 80%of saturated water capacity of sand by controlling irrigation quantity.Rational irrigation of little quantity and many times is an effective method for improving survival percentage and reservation percent of seedling in drought area.Vinyl house has some effect on survival and growth of seedling transplant from far origin area.3.Through introduction and acclimatization for many years,artificial population of Pinus sylvestrs var.mongolica can be survived persistently in arid desert area and has adaptability of growth and development.In the area,daily change of its photorespiration rate shows distinct characteristics of rising rapidly then declining.The declining process of curve is different because of difference of tree's age.Photorespiration rate curve of young tree is fluctuant and it of old tree is gently.Transpiration intensity of 4 years old tree increases gradually in the morning,keep smooth at noon and a period in the afternoon and form an apex before sunset.It of 9 years old tree increases slowly in the morning, then increase rapidly before noon and form an apex in the afternoon.It of 20 years old tree increases rapidly and form an apex in the morning,then form another apex immediately.The appearance time of apex value move forward with increasing of tree's age.