A Study On The Natural Regeneration Of Pinus Densata Forest Burned Areas In Western Sichuan Province, China

Pinus densata, the contemporary geographical distribution center of which is in Western Sichuan province, is an endemic forest type in hengduan mountain region in S.W. China. It undertakes the responsibility of soil and water conservation. The frequent fire caused indirectly by the high altitude and drought in winter and spring makes a great damage to Pinus densata forests. It is in dire need to restore and reconstruct the Pinus densata in burned areas, but in respect of this problem we still lacks theories.The study of this dissertation is part of the forestry key scientific and technological project about the restoration and reconstruction of Pinus densata natural forests in burned areas imbursed by Sichuan Province. It studies the natural regeneration law of Pinus densata and vegetation restoration dynamics from the view of natural regeneration, species diversity, biomass, productivity, soil physical and chemical properties in burned areas so as to provide the partial theoretical basis for natural forest conservation program and the restoration and reconstruction of forest ecosystem in the region of the upstream Yangtze River in Western Sichuan Province.The investigation on the natural regeneration, species diversity, biomass, productivity, soil physical and chemical properties and vegetation change in Pinus densata burned areas at different ages through the "space sequence" instead of "time sequence" method demonstrates that: 'l)The natural regeneration in the shrub-Pinus densata forests' burned areas is better than that in the hevb-Pinus densata forests' burned areas. The Quercus aquifolioides-Pinus densata is the worst. The Pinus densata forests' burned areas distributed berween2800-3600m restore well whereas there is a few naturally regenerated seedling.above 4000m. The natural regeneration on northern and eastern slopes in burned areas is better than that in southern slopes.2)The fire of appropriate frequency and low intensity helps the stabilization and maintaining of pure forests of Pinus densata, which may be the main reason for the more distribution on northern and eastern slopes.3)The species diversity fluctuates largely in the early stage of restoration, but it is not necessary that species diversity increases with the ordinal development of community succession. The community structure changes sharply 4-5 years after burning, and it changes consecutively 8-20 and 20-27 years after the fire. Species diversity index reaches the climax in burned areas 27 years after burning when shade-resistant plants and non-shade-resistant plants exist simultaneously. The 5-year, 6-year and 27-year shrub- Pimts densata forest are high in diversity, but during the three time series, the big community change explains that community with comparatively higher species diversities may not be the most stable to some extent.4)The less density accelerates the seedling of Pinns densata while the over seeding causes the less proportion of total overground biomass. So we should cultivate Pinus densata in appropriate density according to management strategy.