尾巨桉不同造林密度林分生长动态及林木分化特征

Growth Dynamic and Tree Differentiation Characteristics of Eucalyptus urophylla × E.grandis Stand with Different Afforestation Densities

以尾巨桉(Eucalyptus urophylla×E. grandis) 3种不同造林密度(A密度:1 666株/hm^2,B密度:1 250株/hm^2,C密度:833株/hm^2)林分为研究对象,分析了1.5~5.5年生时不同密度林分生长动态、差异及林木分化特征,目的是为尾巨桉纸浆材、胶合板材或大径级锯材人工林培育提供参考依据。3种密度林分树高连年生长量排序是C>B>A,胸径、单株材积连年生长量的排序与树高相同;而不同密度林分蓄积连年生长量的排序则相反。3种密度间尾巨桉林分树高、胸径、单株材积、蓄积量均有显著差异;密度A、B、C的林木胸径变动系数分别是12%、15%、15%,最大与最小变动系数间仅相差3个百分点;林分树高与胸径之比值中,林龄5.5年时最大比值(B密度,比值为140.7)比最小比值(C密度,比值为134.8)仅大4.2%。分析表明,林分树高、胸径、单株材积连年生长量随密度增加而减小,林分蓄积连年生长量则随密度增加而增大;密度小的林分平均树高、胸径、单株材积显著高于密度大的林分,但密度小林分蓄积量则显著低于密度大的林分;林木分化及林木圆满度在不同造林密度间差异较小,且无明显规律。

Using three planting spacing （density of A is 1 666 plants/hm2; density of B is 1 250 plants/hm2; density of C is 833 plants/hm2） as objects, growth dynamics, difference and tree differentiation characteris- tics of 1.5-5.5 years old Eucalyptus urophylla× E. grandis stand were compared in order to provide reference for the cultivation of Eucalyptus urophylla ×E. grandis pulpwood, plywood and large diameter sawn timber. The order of successive annual growth of tree height was C 〉 B 〉 A. The order of successive annual growth of DBH and individual tree volume was the same as tree height, but the order of successive annual growth of stand volume with different densities was opposite. The tree height, DBH, individual volume and volume of stand were significantly different among the three densities ; and the DBH variation coefficients of density A, B and C were 12%, 15% and 15%, respectively. The difference between the maximum and minimum varia- tion coefficient was only 3 percentage points. In the ratio of tree height to DBH, the maximum ratio （the ratio of B was 140.7） was only 4.2% larger than the minimum ratio （the ratio of C was 134.8） when the age was 5.5 years old. Results showed that the tree height, DBH and annual individual volume decreased with the increase of density, while the stand volume increased with the increase of density. The average tree height, DBH and individual volume of low density stand were significantly higher than those of high density stand, but the vol-ume of low density stand was significantly lower than that of high density stand. There was no obvious regularity between tree differentiation, tree satisfaction and afforestation density.