Gap Characteristics And Regeneration In Pinus Bungeana Forests At The Habit Of Crossoptilon Mantchuricum In Huanglong Mountain

With the helps of field investigation,laboratory analysis and various statistical analysis, we studied gap characteristics, regeneration rules and characteristics, dynamics of gap species composition and diversity in Pinus bungeana forests at the habit of Crossoptilon mantchuricum in Huanglong Mountain, and regeneration response of the major tree species in gaps.The results showed as following:In the gaps of Pinus bungeana forests, 57.89% of small (extended gap area≤200 m2), 2.63% of large (extended gap area >800). The larger of the area class, the fewer of the gap numbers. But there were 57. 9% of small (canopy gap area≤150 m2), the ratio of areas are less than large(canopy gap area >600 m2). There were the fewest number and the smallest areas (canopy gap area 450-600㎡). The linear gap density in the forest was 13.2 gaps/km. The most important manner of gap formation was the AF (artificial felling), and the second important manner of gap formation was the S(standing die). The breakage at trunk base and its middle also were the important gap formation. In most gaps there were many gap formations not one only formation. The decay class of maximum gap maker was chiefly B class, the age of gap almost were 50-100 year. Most of the gaps were formed by one gap maker (28.95%), 21.05% of the gaps were formed by no gap maker,average gap maker was 2.11. The ratio of the diameter vs. the gap height of extended gap and canopy gap all centralized at about 1.00-3.00, Gap maker in the forest were consisted of four species, including 56.25% Pinus bungeana, 30.00% Platycladus orientalis, 8.75% Quercus wutaishanica and 5.00% Pinus tabulaeformis. The probability of making gaps was the greatest, when the big trees in the canopy layer got diameter grade<20㎝ and height<5m. And the gap maker diameter grade >60㎝ and height >15m was little to see.Along the gap developmental series of prophase, pro-metaphase, after-metaphase and anaphase, the dominant species in the arbor layer were Pinus bungeana, Quercus wutaishanica, Prunus davidiana and Platycladus orientalis. The dominant species in the shrub layer were Artemisia gmelinii, Lespedeza bicolor, Leptodermis oblonga and Sophora viciifolia, while the dominant species in the herb layer were Carex rigescens, Cleistogenes squarrosa, Aster tataricus and Arthraxon hispidus. In the non-gap stands, there were no dominant species. The similarity coefficients of trees, shrubs, herb species with different gap stages were 0.32, 0.38 and 0.27, while the composition of herb species fluctuated greatly.The regeneration responses could be classified into unimodal curve type, double-modal curve type, no significant response type 3 groups according to quantitative dynamic of seedlings, saplingⅠa nd saplingⅡin the different gap stages, to Pinus bungeana, Quercus wutaishanica, Platycladus orientalis as representative.Natural and human disturbances influenced the patterns and characteristics of gap regenerations in this area, and it was restricted by environmental factors. The regeneration rules were: The species of regeneration seedlings of tree was richer than gap makers and edge-trees, and the ranking of dominance were different with gap makers and edge-trees. The gap dominant species regenerations were affected by various environmental factors and had differences. For instance, the regenerations of Quercus wutaishanica was more influenced by soil factors, Prunus davidiana was more influenced by gap-makers and soil nutrient factors, and Juglans cathayensis was more influenced by terrain factors, pH values and the numbers of gap makers. Moreover, much biodiversity indexes of regenerating seedlings showed that were significantly affected by soil nutrient factors. Therefore, soil appeared to be one of the most important restricted factors of dominant species made biodiversity natural regeneration. The correlation analysis of the gap micro-environment suggested varying controlling factors of Pinus bungeana regeneration developmental stages, and that Light density and soil moisture were the most influential factors on growth of saplings, and litter thickness influented the growth of seedlings; The correlation analysis of slope aspect and population density showed that Pinus bungeana seedlings were more abundant on the Southeast and Southwest slope. Gap regeneration was an important pathway for regeneration of Pinus bungeana communities, and broad-leaved species such as Quercus wutaishanica and conifers species Pinus bungeana in gaps differed from those non-gaps in their regeneration characteristics; Pinus bungeana was most predominant in the early gap regeneration but gradually displaced by other species with time, and accounted for 51.69% of the seedling below age 6 and 1.81%of the seedlings older than 13 years.The diversity index (H′) of abors, shrubs and herbs reached the highest in the conditions of gap gradeⅢ(400-600㎡) and the pro-metaphase of gaps (45-90a), which declined with the area expansion and the age increasing. The general trend of species richness index (R) and pielou evenness index (Js) were consistent with species diversity index H′in the growth forms, while the ecological dominance was opposite to species diversity index. With the change trend of gap sizes and gap developmental stages, the diversity indexes of arbors were more moderate than herbs and shrubs, which were most sensitive to the temporal-spatial changes in the gaps environment.