Abstract:

According to 18 years located study of density and thinning experiments of Chinese fir stands,we can get some results as followings:1.At the same site index class,comparing the unthinned stand with the thinned stand which keeps the same density with the unthinned stand after thinning,their average tree height and dominant tree height have no evident difference. The diameter at breast height(DBH) of thinned stand is much lower than that of unthinned stand. The standing stock of thinned stand is lower than that of unthinnned stand.The total volume (standing stock+thinned tree volume) of thinned stand is higher than that of unthinned stand. The ratio of total volume of thinned stand with high primary density to unthinned stand is higher than that of thinned stand with low primary density to unthinnned stand.The tree height under the first branch of thinned stand is higher than that of unthinned stand,and it is especially evident when the stand is less than 16 years old.The crown diameter of thinned stand is lower than that of unthinned stand,and the difference is remarkable when the stand is 11～16 years old.2.With the same primary density,the ratio of total volume of thinned stand to that of unthinned stand at the high site index class is higher than that at the low site index class.

Key words: Chinese fir, Density, Thinning, Tree volume