Effects Of Thinning On Growth And Natural Regeneration In Pinus Armandii Plantation

Pinus armandii Franch.(Pinaceae:Pinus),an evergreen tree,which is an endemic species of our country,It has become one of the most important afforestation species in the western region because of its simple seedling raising,edible seeds,excellent woodiness and other reasons.In this study,the Pinus armandii plantation in Xiaolong mountain forest area was selected as the research object.The area is located in the northern boundary of China's Pinus armandii distribution area.The community structure is relatively complete and has a long development time,which is of great significance to carry out relevant research and protection work.Based on the investigation of the growth and regeneration characteristics of Pinus armandii plantation under different thinning intensity,this paper aims to explore three scientific problems:1)The effect of tending thinning on the growth and seedling development of Pinus armandi forest retained wood;2)The effect of tending thinning on the natural regeneration characteristics of Pinus armandii plantations;3)The effect of tending thinning on plant diversity of Pinus armandii plantation.Through the analysis of typical sample survey,the above problems are summarized and summarized in order to provide some theoretical and practical basis for the optimization of tending measures of Pinus armandii plantation.(1)Forest thinning played an important role in promoting the growth of remnant trees of P.armandii plantation and improving the seedling regeneration,and the heavy thinning showed the finest effect.The DBH,crown width and individual volume of remnant trees in the stands showed significant difference,but the tree height had smaller variation.The stand volume reduced significantly after thinning,and the heavy thinning showed the biggest drop.Thinning treatment is the effective way to increase the seedling number of regeneration,and the age of 1-3 year-old is the key period of P.armandii seedling growth.(2)Natural regeneration status of Pinus armandi plantation is closely related to forest environmental factors.After thinning,the forest showed obvious habitat heterogeneity,and the seven environmental factors selected to survey could explain the update of seedlings(H?1 m)and saplings(1 m<H and DBH<4 cm).Soil water content and litter thickness are the key factors that restrict the regeneration of Pinus armandii seedlings.The higher soil water content or thicker litter is not conducive to seedling establishmentand growth.Light intensity is a key factor affecting the transition from the growth of Pinus armandii seedlings to young trees,the young trees are more dependent on the light during the development process,If there is no stable lighting condition in the forest,the natural regeneration will be blocked.(3)Heavy thinning could sustain higher level of plant diversity under Pinus armandii plantation in xiaolongshan forest area,and the species richness in shady slope was the largest.With the increasing thinning intensity,species of undergrowth increased,and the plant diversity and evenness indices were highest under heavy thinning intensity;the species richness of shady slope was much bigger than sunny alope,but there was no significant influence on the diversity and evenness indices by slope aspect;there were more common species in sample areas after thinning.However,the similarity coefficient in thinned forest was lower than un-thinned forest.