落叶松人工林冠下光环境对更新幼树生长的影响1）

采用冠层分析系统对落叶松人工林冠下人工更新落叶松幼树的光环境进行了调查。依据调查数据分析了直射光指数、散射光指数、综合光指数与幼树死亡率、树高生长量和地径生长量的关系，结果表明：所选3个光照指数大小对落叶松幼树死亡率、树高和地径生长量均有显著影响，冠下落叶松幼树死亡率随光照指数的增大而减小，树高和地径生长量随光照指数的增大而增大。光照指数在小于0．25时，死亡率最高，树高和地径生长量处于最低水平；当直射光指数和综合光指数在0．25～0．45时，是落叶松幼树在林下维持生存的基本光照平衡区间；在大于0．45时，幼树的保存率和生长表现出了旺盛的状态，说明落叶松在林冠下更新造林的直射光指数和综合光指数不应小于0．45。3个光照指数之间没有显著的好坏差别，呈现了相同的规律性。只是对于幼树死亡率的影响，散射光指数不如直射光指数敏感，同时也说明直射光对于幼树的生存具有更重要的意义。

Effect of Light Environment on Updating Sapling Growth under Artificial Larch Forest Canopy

Using canopy analysis system ( HemiView) under canopy of artificial regeneration artificial larch, we investigated the sapling light environment.According to the survey data we analyzed the direct light index ( DSF) , light scattering index ( ISF) , integrated optical index ( GSF) and sapling mortality, tree height growth quantity and diameter growth.The three selected light index sizes of larch sapling mortality, tree height and diameter growth were significantly affected.Under the canopy of larch, the sapling mortality was decreased with the increase of light index, the growth of tree height and ground diameter was increased with the increase of the index of light.Under the light index of less than 0.25, there was the highest mortality, tree and lowest height and diameter growth.When the direct light index and comprehensive index were in 0.25-0.45, the light was in forest survive basic lighting balance interval for larch sapling.When light index was greater than 0.45, the survival rate and growth of young trees showed a strong state, indicating that larch under the canopy of reforestation di-rect light index and comprehensive index should not be less than 0.45.For stand and fall, there was no significant differ-ence between three light indexes with the same regularity.For the mortality rate of young trees, the sensitive effect of ISF was less than DSF, indicating that direct light was important in the survival of the young trees.