The Study Of Natural Regeneration Of Pinus Bungeana Forest In Huanglong Mountain In Loess Plateau

Pinus bungeana relatively concentrated distributing in Huanglong mountain area of the Loess, and commonly mixed with Pinus tabulaeformis and Platycladus orientalis to form flora communities of high diversity, which also as mainly important habitats of Crossoptilon mantchuricum ranked as the First-grade state protected animal in China. Huanglong Mountain lies along the south part of the Loess, which is regard as a natural barrier against southwards sandstorm from Kuan-chung Plain. Therefore, the study of natural regeneration of Pinus bungeana forest land in this area is not only the important integral part of the Loess ecology research, but it would also play a significantly positive role in native forest diversity protection and agriculture production.Under the background of the basic theory of population ecology, descriptive botany, phytocoenology and biostatistics, from the point of the composition of soil seed banks, individual and vegetation regeneration of Pinus bungeana forest land, by investigating and analytic statistic, this study analyzed the process of natural regeneration of Pinus bungeana forest land, learned the distribution and composition of population in soil seed bank, in addition of the relationship between vegetation and soil seed bank, as well as illustrated the dominant factors of natural regeneration of Pinus bungeana forest land. Through the above work can draw the following conclusion:1) The composition and distribution of soil seed bank of Pinus bungeana forest land:The germination period was identical to the seed period in species structure. The soil seed bank contained 44 species belonging to 34 genera and 26 families in 2009. For individual seed number and species number, a significant difference (p<0.01) was found among soil layers with: 0-5 cm > 5-10 cm > 10-15 cm. Index averages were--Margalef abundance: 3.87, Shannon-Wiener diversity index: 3.63, and Pielou evenness degree index: 1.15. For regeneration and succession, P. bungeana had a stronger regeneration capability with seeds at 39.2% of all tree species. Also, the herbaceous plants were 19.00% more than the woody plants in seeds and 36.36% in species number. Our results show there are significant differences in the vertical distribution of soil seed banks, and the composition of species remained relatively stable in the Huanglong Mountain area.2) The relationship composition of vegetation and soil seed bank:Comparing with the relationship of the dominant species between soil seed bank and above-ground vegetation by similtude analyses, the result shows that the Sorensen index of shrub (0.12)<tree(0.29)<herb(0.53). In the soil seed bank tree and herb species dominant in seeds amount were both late-succession species, and the shrub species is pioneer species; According to the graph of cluster combining, the form of plants individual distribution above the ground vegetation is similar to the seeds distribution in soil seed bank; From the common species both in above-ground vegetation and soil seed bank, the percentage of tree species is 47.83%, which is more than shrub and herb species.3) Individual regeneration of the soil seed bank of Pinus bungeana:The distribution of Pinus bungeana performs regularly. The seeds concentrated under the canopy of their mother tree when they are mature Seed density declined with increasing distance from mother tree.Seed distribution varied with distance (P=0.031).Seed distribution varied with orientation is not significant. Meanly more seeds to the northeast of the mother tree, relatively small to the southwest. The distribution of Pinus bungeana seeds in soil was consistent.Seed density declined with increasing depth of soil(P<0.01).Most seeds were in the litter layer (84%).There were almost no seeds at soil depths greater than 10cm. viable seeds accounted for 14.41 percent 0f total seeds.4) The characteristics of regeneration near the forest edge of Pinus bungeana forest land:The forest edge orienting the northeast is best strongly regenerated of all directions, the northeast secondly. According to age structure, the natural regeneration of the soil seed bank of Pinus bungeana forest land totally shows in increasing development. Regeneration seedlings of 1-5 years is significantly different (p=0.000) from the others more than 5 years. A great loss of regeneration seedlings occurs in the transition of 1-5 to 6-10 years. The regeneration seedlings randomly distribute in the forest edge, increasing with the distance from central forest, three is a significant variation for generation seedlings distribution from contagiously to randomly. By investigating the shape of forest edge, the density and extension length of the regeneration seedlings in the concaved forest edge band in the Pinus bungean forest land.