大强度抚育对油松人工林天然更新的影响

以油松人工林为研究对象,在大强度抚育条件下,通过林分层次结构、各层次林木胸径结构、树高结构及其林木分布格局等指标研究林下天然更新状况,结果表明:油松人工林在22a、32a时分别进行株数强度50%和40%的下层抚育,后经20a天然更新(林分年龄52a),林分形成明显层次结构,分为主林层、演替层及更新层,整个林分林木胸径、树高结构均呈多峰分布,其中主林层、演替层林木胸径和树高结构均呈单峰山状分布,更新层林木胸径和树高结构呈多峰分布,各林层平均胸径分别为23.2cm、12.6cm和3.1cm,平均树高分别为18.4m、14.5m和2.8m,而对照标准地胸径、树高结构均呈单峰分布,平均胸径、树高分别为18.6cm及17.9m;主林层、演替层各层林木空间分布呈均匀分布,密度分别为840株/hm~2和1 125株/hm~2,更新层林木空间分布呈聚集分布,密度为675株/hm~2,对照样地林木空间分布偏向均匀分布,密度为1 605株/hm~2。

Effects of high intensity thinning on natural regeneration of Pinus tabulaeformis

Pinus tabulaeformis plantation was the study object of this article.Forest storey structure,DBH,height and distribution structure in each storey were the aspects of the compreensive analysis for effects of tending on natural regeneration.The results showed that.:the structure of the forest storey was obvious after twice thinning,for one in 22 a (the number intensity as 50％) and the other in 32 a (the number intensity as 40％).The diameter and height distribution appeared to be mountain-like curve at main storey and succession storey,and regeneration storey,which appeared to be multiple-peaked distribution.The average DBH of each storey were 23.2 cm,12.6 cm and 3.1 cm respectively,and the average height were 18.4 m,14.5 m and 2.8 m respectively.The diameter and height of trees at the sample plots appeared to be single-peaked distribution,the average of DBH and height of which were 18.6 m and 17.9 m respectively.The main storey and succession storey showed to be the uniform distribution,the desity of which were 840 trees/hm2 and 1 125 trees/hm2,while the regeneration storey showed the aggregated distribution,the desity of which was 675 trees/hm2.The stand appeared to be a uniform distribution at the control sample plot,and the density was 1 605 trees/hm2.