林分密度对邓恩桉生物产量及生产力的影响

Effects of Stand Density on the Biomass and Productivity of Eucalyptus Dunnii

对湘南低山丘岗区密度为1 110、1 667和2 500株.hm-2的8年生邓恩桉Eucalyptus dunnii丰产示范林生物量进行了测定.结果表明:单株生物量随林分密度的增加而明显减小,低密度林分林木平均木的生物量是高密度林分的1.22倍;林分生物量随林分密度的增加而增加,高密度林分比低密度林分高出271.26 t.hm-2;各密度林分的年均净生物量分别为32.35、43.97和59.51 t.hm-2a-1,高于杉木中心产区杉木人工林的水平,林分各组分的生物量随林分密度的增大而增大,并出现干>根>枝>皮>叶的规律;林分结构以中密度林分合理,叶面积指数高,干材生物量达61%以上.邓恩桉在湘南低山丘岗区发展潜力大,可作为该地区短周期工业用材林培育造林树种.

An investigation was made on the biomass of 8-year-old Eucalyptus dunnii forest with the densities of 1 110, 1 667 and 2 500 trees . hm^-2 in the low hilly area of South Hunan. The results show that the biomass of individual stem decreases distinctly with the increase of the density and the biomass of stand with low density is 1.10 and 1.22 times that with middle and high densities ; that stand biomass is raised with the increase of density and the stand biomass in the forest of high and middle densities is 217.26, 92. 96 t . hm^-2 higher than that in low density forest; that the change pattern of annual net biomass agrees with that of the stand biomass and the average biomass of stands with the three density levels reach 32.35, 43.97 and 59. 51 t . hm^-2a^-1 respectively, which are higher than those of Chinese fir plantation in the central planting area; and that the component biomass increases with the stand density, which exhibits a pattern of stem〉root〉branch〉bark〉leaf. A reasonable stand structure is observed in the stand with middle density, in which the index of leaf area is highest and stem biomass reaches above 61%. It is concluded that Eucalyptus grandis×urophglla to be used for wood pulp is suitable for plantation in the north border and the low hilly area of South Hunan.