Structure Analysis And Close-to-natural Operation System Design For Pinus Tabulaeformis Plantations In Northern China

Most of Pinus tabulaeformis plantations in northern China have problems with bad timber quality, high stand density, single layered forest structure, and lack of mixture. For those reasons, this study used a new silvicultural concept"close-to-nature forest management"in Xishan and Huanglong Pinus tabulaeformis plantations and was hopefully to probe a suitable way to improve the forest development and regeneration.We selected 9 managed sample plots and 6 unmanaged sample plots in Xishan and Huanglong Mountain whose total area is 2.08 ha. The first survey was implemented at 2005 in Xishan Mountain and 2004 in Huanglong Mountain. We made forest management preliminary design rely on close-to-nature principle and data from reconnaissance. According to the design, competed tree selective cutting was implemented in the managed plots at the same winter. The second survey was carried out at 2007 in Xishan Mountain and 2008 in Huanglong Mountain. The results show that initial stand density significantly affects the forest stand growth; management positively degraded the stand density, stand basal area, and also the stand volume in the first 4 years, but had no effects on height increment and DBH increment. Target trees grew faster in managed plots than in unmanaged plots. There were more tree species and amount of young trees per ha in the managed stand, but were lack of target young trees in the forest stand which needs assistant of artificial regeneration methods, such as seeding and planting. Logging negatively affects young trees, especially on the trees which are higher than 50cm. According to the analysis of forest structure and natural regeneration, we designed close-to-nature forest management system for Pinus tabulaeformis plantations in Xishan and Huanglong Mountain, which contains forest development stage and relative tending methods, forest development type, and target tree management system. We suggest that, in the future management, artificial regeneration method should be implemented; young target trees should be protected by fence.