Research On The Availability Of Seeds Input And Output In The Introduced Sand Fixation Forest Of Pinus Sylvestris Var.mongolica

In this paper,Taking Pinus sylvestris var.mongolica sand fixation forest land of different age,different site and different density as the research object,the input ability,output ability,dynamic law and availability of the seeds were studied by investigating and monitoring the characteristics of seeds production,seeds rain,canopy seeds bank and soil seeds bank,combining with the indoor seeds germination experiment and field supplementary sowing experiment.The main results are as follows:There are significant differences in seed production characteristics between major or minor years,and 2019 is significantly better than 2018.The seed production characteristics are as follows:the stand density is 800-1000 plants/hm~2,the site is west slope and the age class is21-30 a and 31-40 a,which can provide sufficient and high-quality seed guarantee for seed input.The input of seed rain with certain spatial-temporal pattern differences can last for one year.From October to March of the next year,it mainly spreads to the East,South and north of the mother tree.And from March to June,it mainly spreads to the South and North.The seed abscission of canopy bank is mainly concentrated in October,and the cone abscission is concentrated in May and June of the next year.The seeds in the soil bank are mainly concentrated in 0-2 cm soil layer.The seed germination percentage of Pinus sylvestris var.mongolica stands with density of less than 800 plants/hm~2,slope and forest age of 10-20 a and 21-30 a is the highest,while the seedling drought resistance of Pinus sylvestris var.mongolica stands with density of 800-1000 plants/hm~2,flat land and forest age of 21-30 years is the best.The seedling emergence percentage of Pinus sylvestris var.mongolica is the highest in May.And the seedling emergence percentage is the highest in shady slope,small forest window and grassland,while the seedling survival percentage is higher in shady slope,middle forest window and bare land.Artificial seed collection significantly reduces seed input(p<0.05).The yield loss rates of cones and seeds are respectively 32.87%and 48.64%.60.79%of the total seed yield are eaten by animals,0.09 of which are still existed on the canopy.Only 39.12%of the seeds form the soil seed bank.The effective sprouting seedlings account for only 0.83%of the total seed yield,and the effective surviving seedlings account for 0.043%of the total seed yield,which is difficult to be effectively renewed.In summary,artificial seed collection and animal feeding are the main ways of seed loss,which greatly reduces the availability of seed input.The dynamic input of canopy and the storage pattern of soil seed bank can reduce the risk of seed loss,but the poor habitat and extreme weather conditions seriously restrict its effective output,which makes the natural regeneration of introduced Pinus sylvestris var.mongolica difficult to carry out effectively.There are 42 figures,18 tables and 75 references in this paper.