Characteristics Of Seeds And Fruits Of Pinus Tabulaeformis Plantations In Different Vegetations On Loess Plateau

Pinus tabulaeformis,is the main afforestation and greening tree species in the Loess Plateau,which has the function of sand fixation and water conservation.In recent years,the afforestation area of Pinus tabulaeformis in the Loess Plateau has increased year by year,however,there is a common phenomenon of early fruiting or excessive fruiting of stands.Because of the limited seed production capacity of the improved seed base,it is difficult to meet the demand of seed production,and the phenomenon of early and random seed picking is more common.In order to further understand the inner quality of seeds in Pinus tabulaeformis plantation,In this study,the seeds of Pinus tabulaeformis were studied.Typical plots and mother trees were selected from young and middle aged forests in the forest belt,forest grassland belt and grassland belt of the Loess Plateau.Collecting cones and seeds,measured The morphological index,vigor index and seedling character index of cones and seeds,Comparative study on seed characteristics of Pinus tabulaeformis Plantation with different vegetation,The purpose of this paper is to provide theoretical basis for the selection of good provenance,the site selection of improved seed base and the regional selection of seed collection for Pinus tabulaeformis plantation on the Loess Plateau.The main results of this study are as follows:(1)The shape and size of cones and seeds morphology of Pinus tabulaeformis plantation in forest belt,forest grassland belt and grassland belt are obviously different.The cone and seeds of middle age forest is larger than that of young forest.Cone length 41.88 mm~70.27 mm,Seed length 5.39 mm ~8.56 mm.The cones and seeds of young forest are the largest in the forest belt,Forest steppe belt take second place,Steppe belt is the smallest;the middle age forest steppe belt is the largest,the forest belt is the second,and the steppe belt is the smallest.(2)Significant differences in seed germination characteristics of young forest from three vegetation belts,Seed germination of young forest in forest belt is the best,followed by forest steppe belt and steppe belt;Middle-aged Forest in forest steppe belt is the best,the forest belt is the second,and the steppe zone is the worst.The characteristics of Middle-aged Forest seed germination and seedling root system were better in the three belt than the young forest,Germination percentage 32%~99%,Root surface area2.19cm2 ~12.95cm2.(3)Under the same cultivation conditions,the seedling growth status of young and middle aged forests developed by steppe zone,forest steppe belt and middle age forest belt was relatively good,Seedling height 3.9cm~6.4cm and 1.6cm~8.1cm.The seedling characters of young forest seed from steppe belt were better than that of forest steppe zone,and the forest zone was the worst;Middle-aged forest steppe zone is better than forest belt,and steppe zone is the worst.(4)Under the same cultivation conditions,there were significant differences in the biomass of seedlings developed from three vegetation with seeds.The seed seedling biomass of young forest and middle age forest from grassland belt is relatively large,Seedling fresh weight 0.21 g /plant~2.35 g /plant and 0.31 g /plant~2.61 g /plant.The seed seedling biomass of young forest from the forest steppe belt is the largest,followed by the steppe belt,and the forest belt is the smallest;The middle age forest steppe belt is the largest,the forest belt is the second,and the steppe belt is the smallest.