Effects of different thinning intensity on seed production stands of Pinus koraiensis in Menjiagang Forestry Station

Through statistical analysis on fourteen traits of old seed production stands of Pinus koraiensis with density 300, 450,600,700 and 1 300 individuals / hm2( this thinning density as control) after thinning forty years in Menjiagang Forest Farm,the results showed that the thinning exerted significant influences on all traits. Except the branch height,the average values of other traits were higher than those before thinning,for example,the bearing yield per tree,crown volume and bearing yield per hectare increased 47. 79% 、33. 6% and 28. 65%,respectively. Moreover,the complex relativity among fourteen traits was presented. All traits could be divided into three categories which represent crown,seed quality and bearing trait by means of cluster analysis and principal component analysis. After compared the weighted sum of each principal component score of three categories traits,the best thinning intensity for forty years old seed production stands of P. koraiensis in Menjiagang Forest Farm was 450 individuals / hm2.