长白山次生杨桦林采伐林隙乔灌木幼苗更新比较研究

Study on Seedling Regeneration of Arbor and Shrub in Logging Gaps in Populus davidiana-Betula platyphylla Secondary Forests in Changbai Mountain

从林隙大小和林隙年龄2个方面初步研究了杨桦次生林经营采伐形成的林隙及其更新特征。结果表明：冠林隙面积〈50m^2占7％，50～100m^2占21％，100～150m^2占36％，150～200m^2占29％，〉200m^2占7％。28．6％的林隙呈圆形，71．4％的林隙呈椭圆形。椭圆形林隙中55％为南-北方向，30％为东北-西南方向，15％为东南-西北方向。林隙一般由7～10株山杨、白桦或山槐被伐后形成。林隙内更新幼苗的密度和生长状况优于非林隙林分。在林隙形成初期，灌木幼苗在林隙更新中占绝对优势，但随着林隙形成年龄的增加，灌木将逐渐丧失其优势，乔木的优势则逐渐上升。除50～100m^2林隙外，乔木幼苗的平均高和平均基径均大于灌木，但都在100～200m^2林隙内最大。各大小级林隙内更新的主要乔木中阳性树种占大多数，但优势种各不相同。

Regeneration in relation to logging gaps sizes and ages was investigated in Populus davidiana-Betula platyphylla secondary forests in Changbai Mountain. The research result showed that there were 7% （canopy gaps area 〈 50 m^2 ） ,21% （50 - 100 m^2 ） ,36% （ 100 - 150 m^2 ） ,29% （ 150 - 200 m^2 ） ,7% （ 〉 200 m^2 ） in the proportion of gap sizes. 28.6% of gaps shape were rotundity and 71.4% were oval. 55% of the oval gaps lay in N-S direction, 30% lay in N-E to S-W direction and 15% lay in S-E to N-W direction. Gaps were usually formed after 7 - 10 trees logged which were mainly composed of Populus davidiana, Betula platyphylla and Maackia amurensis. The seedlings was absolutely dominated by the shrub at the initial stage of logging gaps, but the dominance of the shrub seedlings would weaken step by step. At the same time, the advantage of arbor seedlings would raise correspondingly with the increasing gaps age. The density, mean high and mean basilar diameter of seedlings growing in the logging gaps were higher than those in non-gap. The growth of seedlings was the best in 100 -200 m^2 gaps and arbor seedlings surpassed shrub seedlings in gaps except 50 - 100 mE gaps. The dominance species mainly composed of intolerant species were different in gaps of different sizes.