以林窗北缘为中心, 研究了西双版纳地区橡胶林林窗及周边N-S 样带上光照水平梯度分布。 结果表明:林窗的发生导致光照明显增加, 从林内到林窗中央, 光强呈明显增大趋势, 上午雾未消退时, 相对光照强度水平梯度变化曲线峰值出现于林窗中央, 午后雾消退后, 林窗边缘为相对光强梯度变化最甚的地段, 峰值由林窗中央向林窗北缘移进。 林窗边缘、林窗中央及林内光照强度日变化曲线均为不对称的单峰型, 但峰值出现时间和振幅不同。 在太阳高度角、方位角、天气状况、林窗边缘乔木高度( H) 与林窗直径( D) 之间( H/ D) 、林缘乔木冠层结构等的影响下,林窗及不同方位边缘的光照状况差异很大。 光照的影响范围从林窗北缘深入至林内 12 m, 林窗南缘深入至林内 8m, 林窗边缘侧光随深入林内的距离呈指数递减。 西双版纳多雾的环境条件对林窗及周边相对光照强度的影响不容忽视。晴天林内透光率日变化曲线呈倒 Z 字型, 林窗边缘及林窗中央相对光照强度日变化曲线为 M 字型, 均在早晚出现峰值。
 

Taking the north-edge of gap as a central point, the character of temporal and spatial distribution of sunshine were studied along sample line from the interior of forest to the center of gap in rubber forest in dry season in Xishuang banna .The results indicated that creation of gaps result in significantly increasing of sunshine .The sunshine in day w as the open >the center >the interior, When the clouds did no t disappear and the fog did not lift, the maximum value of horizontal variation of relative light intensity ( RLI) occurred in the center of gap.After the clouds disappearing and the fog lifting, variation of RLI w as significant at the edge of gap, at same time, the maximum value was shifted to gap-edge .The curve of diurnal variation of the light intensity ( LI) is left-leaning singlepeak, but degree of respective variation is different .Because of the influence of the angle and the azimuth of the sun, w eather, the ratios of height of edge-arbor to diameter of gap and canopy structure of edge-arbor, the condition of sunshine of gap and its edge is sig nificant .Gap influences ex tent on light was up to 12 m and 8 m into forests from the edge of north-facing and south-facing direction.Light from gap-edge extending into the interior decrease acco rding to index curve;Condition of foggy environment have a significantly influence on LI of gap and its edge ;Curve of the diurnal variations of transmission rate of the interior was in the shape of “Z” in clear day .Curve of the diurnal v ariations of RLI of the center and the gap-edge w as in the shape of “M ” in clear day , peak value all occurred in morning and evening .