关键词: 杨树, 密度效应, 配置模式, 生长过程

Abstract:

Research on the dynamics between the density,planting composition,average DBH,height,canopy width,tree volume,forest volumes,and the changes through the growth of the stand of a natural rain-fed,sand-fixing,Chifeng-36 poplar forest in Horqin sandy land of dry sub-humid climate reveals that:1)Planting density shows no discernable effect on the growth of 1～5-year-old stands.Densification of the stand will effectively increase the forest volume per hectare.When stands enter 6～11 years of age,the effect of planting density on the forest growth starts to mount,in that the growth rates of the DBH,height,and timber volume will expedite as the stands age.At age 11 and above,such effect appeases.Among the all stands involved in the experiment,the volume reaches the maximum(153.39 m3·hm^-2)with a stand of 825 stems·hm^-2.The volume decreases as the forest density changes from 540 stems·hm^-2 to 420 stems·hm^-2 and minimizes at 35.18 m³·hm^-2 with a density of 1 215 stems·hm^-2.2)The average DBH and the timber volume of single plant along the stand edge are 20%～70% and 90%～260% higher respectively than those at the forest core.Moreover,the growth along the stand edge is even more remarkable when the stand has a low density.3)Holding constant the density at 500 stems5hm^-2,the DBH,height,and timber volume of a 13-year-old,one-row-and-one-belt sand fixation forest are 37.4%,17.4% and 81% higher than those of a evenly planted stand,respectively.The same measurements of a 10-year-old,two-row-and-one-belt sand fixation forest will be 19.8%,16.2% and 64.8% higher than a evenly planted stand,respectively.

Key words: Chifeng-36 poplar, density effect, spacing pattern, growth process