栽植密度对毛白杨无性系生长性状遗传变异的影响

为了选择最适栽培品种及栽培措施，通过毛白杨无性系区域化密度栽培试验（以4个无性系和7种栽植密度采用完全随机区组设计，以河北威县营造的试验林为研究对象），揭示密度对无性系生长的作用规律。结果表明：从造林当年开始，树高、胸径在无性系间就具有显著差异，S86和BT17无性系明显优于1316和B331无性系；密度对胸径生长的显著影响在造林后2年出现，且显著程度随林龄增大而增大，密度对树高生长的影响在造林后2~3年差异最大；密度×无性系互作对4年生林分胸径、树高的影响不显著；833株/hm2是4个无性系密植的最小底线，高于该密度无性系对胸径的影响，随林龄和密度增大而减小，低于该密度随林龄增大而增大、随密度减小而降低；高密度下无性系对树高的影响随林龄增大或密度减小呈先降低后增大趋势，低密度下随林龄增大呈先增后降趋势；无性系对胸径遗传变异系数的影响在密度间差异不大，无性系×区组互作变异系数及基因型内株间变异系数2年生前在密度间差异较大；无性系×区组互作对树高遗传变异系数的影响随年龄增大呈先增后减趋势，而树高在株间的变异系数随年龄增大而增大；以无性系均值计算的树高广义遗传力在密度间不显著，以单株值计算的树高广义遗传力在密度间差异显著，而2种方式计算的胸径广义遗传力在密度间差异均极显著，在年龄间差异均不显著。

The Effect of Planting Density on Heritability of Growth Traits in Populus tomentosa Clones

In order to reveal the planting density effect on the growth of Populus tomentosa clones and put forward the most suitable cultivated white poplar varieties and management for different region through the regionalizing spacing cultivation experiment,to study spacing effect on genetic parameters for growth traits of Populus tomentosa clones,and to assess genotype by spacing interaction,the experiments including 4 clones and 7 spacings were established with completely random block design in Weixian County,Heibei Province. Results indicated that both height and diameter at breast height（DBH） between clones were always significant at the 1% level of probability.S86 and BT17 clones were superior to 1316 and B331;Effect of planting density on DBH was significant after one growth period at the 5% level probability and increasingly marked with age, on height was most significant at only 2,3-year ages.Spacing × clone interaction was not remarkable for 4-year-old stand.For 4 clones,planting density with no less 833 trees/hm 2 was used to establish closer plantation.The difference of DBH between clones gradually decreased with density and age increasing when spacing exceeded 833 trees/hm 2 ,declined with spacing narrowing and went up with age growing less than 833 trees/hm 2 .But for close stand,the clonal genetic effect on H presented the trends to decrease at first and then increase with aging and spacing decreasing.For rare stand,there was a contrary fluctuation with aging. Planting density had not significant influence on the coefficient of genetic variation（CV） between clones for DBH.But the CV of clone by block interaction and of inner-clones were larger before two years than after two years.For height,the CV of inter-clones and of clone by block interaction were increasing with age at early growth period and then decrease with age,but CV of inner-clones gradually increased with age.The broad hereditability（H2） of DBH was remarkably different between spacings at the 1% level probability,but not significant between ages at the 5% level probability.H2 of height,derived from clone mean value,was not marked between spacings at the 5% level probability,but H2 of height calculated by clone individual value was significant difference between spacings at the 5% level probability,but H2 of Height calculated by both of methods was not significant between ages at the 5% level probability.