华北落叶松人工林生长季内的林冠结构和光分布

A study on the canopy structure and light distribution of \%Larix principis ruppurechtii\% during the growing season

根据 1 991～ 1 992年生长季中 2 9d的观测资料和 32株伐倒木分层测定数据 ,对华北落叶松人工林的林冠结构、光合有效辐射分布规律进行了分析研究 .结果表明 ,华北落叶松林木一级侧枝倾角随枝龄增长而增大 ,随着枝高度增加而减小 ;枝长随着枝高度降低而增大 .林分叶面积指数约 3/ 5分布在冠深 2 .5～ 4.5m (高密林分 )和 3.5～ 5 .5m (低密林分 )的空间内 .叶面积指数、枝表面积指数随冠深的累积分布曲线均呈S型 .生长季林冠对光合有效辐射的日平均透过率和反射率均为 7月 <8月 <6月 <9月 ,吸收率则为 9月 <6月 <8月

Based on data of photosynthetic available radiation (PAR) measured in two stands for 29 days during the growing seasons, and data of 32 sample trees measured by the clip method, the light distribution and canopy structure during the growing season were studied for \%Larix principis rupprechtii\% plantation stands in North China. The inclination angles of primary branches increase with their ages and decrease with their base heights. The most of the leaf area index of stands distributed in the layer located in 2.5～4.5 m of the canopy for the high density stand (3?227trees hm -2 ) and that located in 3.5～5.5 m for the low density stand (2?000trees hm -2 ), from top of the canopy downwards. The cumulative distribution curves of the leaf area index and the total surface area index both were S-shaped, the total surface included the leaf area and the surface area of branches and stems. In high density stand, the daily mean transmissivity ranged from 1.69?% to 5.18?% PAR, reflectivity within 3.72?%～6.21?% and absorptivity within 89?%～95?%, and in the low density stand, those were within 2.38?%～6.34?%, 5.18?%～7.01?% and 88?%～93?% respectively. In the growing season, the values of transmissivity and reflectivity both were July <August <June < September, and the values of absorptivity were September<June<August< July.