The Intraspecific Competition And Density Effect Of The Aerial Seeding Chinese Pine(Pinus Tabulaeformis) Forest In The Gully And Lilly Region Of Loess Plateau

The Chinese Pine(Pinus tabulaeformis) is the brief planted forest type in the hilly and gully region of Loess Plateau, which is distributed a widely geographic range with high productivity and ability of soil and water conservation. The Chinese Pine plays an important role in the developing and controlling of the Loess Plateau. Due to the Chinese Pine with high adaptability, it becomes the major aerial seeding species in the Loess Plateau. But, the properties of aerial seeding pine were little studied. The 30 year-old aerial seeding Chinese Pine forest as the object of study in Yichuan, the relationships of intraspecific competition and the density effect were researched, and the major conclusions as:1. The neighborhood range of lower diameter size was 3m, which gradually became large with the diameter size increasing, by using the improved individual competition model. The total competition intensity became intensively for objective stand because there were more neighbor trees, and the relation between the competition intensity and distance from objective stand was CI=Alnd+B.2. The competition intensity was gradually decreasing along the DBH increasing of objective tree, the function is CI=AD-B, and the total competition intensity had little changed when the DBH of objective tree were more than 20cm.3. The slope gradient influenced the pine forest, and the most pine forests were 22°-32°slope range.4. The forest density seriously affected uniformity of pine DHB, and the density was large or few, the differentiation of stand diameter size were not markedly. When the density was higher, there were function D=ap-b, H= ap-b, (D/H)= ap-b among the height (H), blade diameter length ratio (D/H) and stand density(p).5. The relationship between average biomass per stand and average density was consistent to-3/2 self-thinning law in general, and there were few deviation with the laws in little sunshine slope.6. The forest density played key influence for seedling renew of the under forest. When the density is 1500～2000/ha of 30-year-old aerial seeding Chinese Pine forest, the stand well developed.