4个银×新杨无性系生长特性

对伊犁地区筛选的4个银×新杨无性系生长特性进行研究。结果表明，银×新杨4个无性系的高生长要早于胸径生长，生长中后期单株之间差异明显；树高连年生长量最大值与平均生长量最大值几乎同步出现，胸径亦如此，树高连年生长量在第4～6年时与平均生长量相交，胸径连年生长量和平均生长量在第6～7年时相交。从18a生的4个无性系生长过程来看，生长可分为3个时期：第O～6年为幼树期，树高、胸径生长比较快。第7～14年为速生期，树高、胸径生长急速上升。第15～18年为近熟期。银×新杨材积的平均生长量与连年生长量在第16年左右时相交，达到数量成熟，此时可进行轮伐。

Growth Characteristics of Four Clone of Populus alba X Populus bolleana

Growth characteristics of Populus alba ）〈 Populus bolleana plantaion in Plain Forestry Farm of Ili Area had been studied. The results showed than tree height growth of four clone of Populus alba ）〈 Pop- ulus bolleana was earlier than the breast diameter growth. There were significant differences among single plants in the middle and later periods of plant growth. The maximum of current annual increment and aver- age annual increment of tree height appeared nearly synchronously, so did the breast diameter. The current annual increment of the tree height and the average annual increment intersected with each other nearly in 4th--6th year. The current annual increment of breast diameter and the average annual increment intersec- ted about in 6th--7th year. But the maximum of current annual increment of timber volume appeared much more earlier than the maximum of mean annual increment;From the view of growth process of four clone of Populus alba X Populus bolleana produced 18 years ago,the growth can be divided into three periods; 0-6 years were the young treelet period,during which the tree height and breast diameter grew faster; 7-14 years were the high-growing period, during which the tree height and breast diameter grew at high speed. 15-18 years were the near mature period. The average current increment of Populus alba ）〈 Populus bolleana and current annual increment intersected with each other about in 16 years with quantitative ma- ture,in this moment,the rotation of humbering can be operated.