“三北”防护林二白杨生长分析

ANALYSIS OF THE GROWTH FOR POPULUS GANSUENSIS IN "THREE-NORTH'S" SHELTER-FORESTS

二白杨(Populus gansuensis)是一个强阳性树种,极耐干燥、耐寒,抗风沙,在河西的盐碱化和较干旱的土壤条件下,能靠微弱的季节性地下毛管上升水生长,在良好的水分条件下生长尤其迅速。该项研究的野外调查于1980—1981年在甘肃河西石羊河中游进行。研究地区年平均降水量115.4mm,年平均水面蒸发量2681.8mm,年平均气温7.8℃,气温极值为39.5℃和27.3℃。土壤为荒漠化草甸土。研究对象为在灌溉条件下的二白杨人工林。

The annual biomasses of trunk, branch and leaf of Populus gansuensis (Populus nigra var. italica×P. siminii), as a single tree and population, have been calculated by analogy simulation and average treemodular standard tree method respectively in this paper. The growth analysis of this tree species have also been carried out by classical method. The results are as follows: (1) By calculating the existed biomass, the percentage of trunk, branch, and leaf to the overground part of a tree(S_1%, B_1%, L_1%), tended to be stable from the 8th year, which is 77%, 18% and 5% respectively. (2) Based on the dry matter accumulated over 16 years, the percentage of leaf to the overground part of the tree amounted to 21.5%, and it would raise with the increase in age. (3) The leaf area ratio (LAR) of both an individual tree and a population trended to decrease during the investigation. The net assimilation rate (NAR) and the relative growth rate (RGR) tended to fall from the 8th year. (4) The leaf area index (LAI) of a population shot up with the increase in age during the investigation. The complex growth rate (CGR) raised sharply after the 5th year, and amounted to the maximum at the 8th year when the LAI was 9.1.