Abstract:

With the Pinus taiwanensis plantation in the multi-functional forest management sample base of Huangbaishan Forest Farm as the object,the randomized blocks were used to set up the fixed sample plot,and the first thinning test was carried out in the young forest,including the intensive thinning(45%),moderate thinning(34%),weak thinning(23%) and control(no thinning).When the Pinus taiwanensis plantation entered on the age of the half-mature forest,near mature forest,and mature forest,the second,third and fourth thinning tests were carried out in succession,and all were carried out on the basis of the previous thinning,in which the intensive thinning(30%),moderate thinning(20%),weak thinning(10%)and control(no thinning) were done.Study was conducted on the effects of different thinning intensities on the growth of Pinus taiwanensis plantations at different ages during the cultivation period of Pinus taiwanensis plantations.The results showed that:(1)In the same age class,the growth rate of DBH,tree height,volume of individual tree,basal area and volume increased with the raising of thinning intensities.(2)The intensive and moderate thinning of young forests,and the intensive thinning of half-mature forests and near-mature forests significantly promoted the growth of DBH.The thinning of mature forests did not significantly promote the growth of DBH.(3)In any age class,thinning had no significant effect on growth of tree height.(4)The intensive and moderate thinning of young forests as well as the intensive thinning of half-mature forest and near-mature forests significantly promoted the growth of volume of individual trees,and the thinning of mature forests did not significantly promote the growth of volume of individual trees.(5)The basal area of residual trees was reduced with the increase of thinning intensities,and thinning had no significant effect on the total basal area.(6)The volume of residual trees was reduced with the increase of thinning intensities,and thinning had no significant effect on the total volume.As far as the management of Pingus taiwanensis plantation is concerned,after the young forest section of the forest was closed,the first thinning begins,and the intensity and moderate thinning are appropriate;The second and third thinning operations of middle age forest trees and near-mature forest trees are carried out,mainly by intensive thinning;The fourth thinning of mature forest section has no significant effect on the growth of Pinus taiwanensis forest and can be abandoned.

Key words: Pinus taiwanensis, thinning intensities, growth rate, age class, stand growth