马尾松天然次生林间伐效应研究

于平均年龄为23年生、地位指数为14和12的2种立地的马尾松天然次生林中,分别设置固定标准样地,并分别设计5个和6个密度水平,对其抚育间伐4年后的间伐效应进行研究。结果表明:不同地位指数的林分,其间伐前或间伐后立木径级分布均呈现正态分布的规律;间伐前林分分化强烈,立木径级大小悬殊;间伐后林分最小株距和平均株距较接近,大径级林木比例提高;间伐4年后平均径级左右的立木比例明显增加。间伐4年后,当14地位指数林分的密度大于1 500株/hm2,12地位指数林分的密度大于1 950株/hm2时,其胸径离散度较间伐当年间伐后的反而明显增大;平均胸径和单株材积的增长均随保留密度的加大而减小,但单位面积蓄积量增长则在其适宜密度时最大;不同保留密度各处理间平均胸径、单株材积以及单位面积材积增长的差异均达极显著,但树高和比重增长的差异均不显著;间伐各处理的平均胸径、单株材积以及单位面积材积增长均大于对照;14地位指数马尾松林以保留密度为1 500/hm2处理的单位面积材积增长最大,增长30.29%;12地位指数马尾松林以保留密度为1 950/hm2处理的单位面积材积增长最大,增长24.38%。

Effect of thinning on natural secondary forestry of

Set five and six density levels respectively in site index 14 and 12 natural secondary forestry of 23-year-old Pi- nus massoniana, the effect of thinning on natural secondary forestry of Pinus massortiana after 4 years was studied. The results showed that, the diameter-class distribution of different site index stand before and after thinning showed normal distribution. Before thinning, there were strong differentiation in stand and great disparity in diameter-class. After thinning, the smallest interplant spacing of stand was more close to the average interplant spacing, and the percentage of big diameter-class stand increased, while the percentage of average diameter - class stand increased significantly after 4 years. After 4 years of thinning, when stand density of site index 14 and 12 was greater than 1 500 tree/hm^2 and 1 950 tree/hm2 respectively, DBH dispersion increased markedly compared with the current year of thinning. The growth of av- erage DBH and individual volume decreased with the increase of reserve density, but the growth of stock volume per unit area reached maximum at the suitable density. There existed very significant difference in average DBH, individual vol- ume and unit area volume growth among different reserve density, but there were no significant difference in height and specific weight growth. The growth of average DBH, individual volume and unit area volume with treatment of thinning were higher than CK, the unit area volume growth of site index 14 P/nus masson/ana forest was the greatest when the re- serve density was 1 500 tree/hm^2, which reached 30. 29%. And the unit area volume growth of site index 12 Pinus mas- soniana forest was the greatest when the reserve density was 1 950 tree/hm^2, which reached 24. 38%.