Thinning effects of Pinus massoniana plantations in the southern region of Hunan province

The thinning effects in Pinus massoniana plantations were studied by using biomass increment as quantitative indexes.The results show as follows.Regardless of site conditions,the individual biomass of P.massoniana plantations increased positively with the raise of thinning intensity.The average per plant biomass of the stand with the site index of 14 was 1.31 times more than the control plot,the biomass of intensity intermediate felling of the stand was 1.49 times more than that of the check plot,and the first thinning for the stand of site index of 14 was the suitable moderate thinning.The stand biomass was inversely proportional to thinning intensity,namely the greater thinning intensity was,the smaller the existing biomass was.The thinning stand productivity had the same change law as the stand biomass.In six years with thinning,stand productivity was greater than the average.The stand productivity with the site index of 14 by moderate thinning was 120% of the average.For the stand with the site index of 14,light thinning can be executed at 16-year-old.For the stand with the site index of 12,no thinning need be executed after the 1st moderate thinning if the stand was for producing small-diameter lumber and mid-diameter lumber.It was proved that thinning could help to raise the stem-wood percentage of the stand,which increased with the increase of the thinning intensity,and to make the stem straight and fatness,and to promote the wood specifications and wood economic value.