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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NS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12m,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。
With the center of the northern margin of the forest gap, the horizontal distribution of light irradiance on the rubber forest gap and surrounding NS samples in Xishuangbanna was studied. The results showed that the occurrence of forest gap led to a significant increase of light intensity. From the forest to the center of the gap, the light intensity increased obviously. When the morning fog did not subside, the peak of relative light intensity gradient appeared in the center of the gap, After the edge of the gap, the relative gradient of light intensity changes the most of the area, the peak from the center of the gap to the northern margin of the gap into the gap. The diurnal variations of light intensity at the edge of a forest window, the center of a forest window, and the light intensity in a forest are asymmetric unimodal, but the peak appearance time and amplitude are different. Under the influence of solar altitude, azimuth, weather conditions, tree height (H) at the edge of a forest window and diameter of a forest window (H / D), canopy structure of tree margins and the like, The edge of the light conditions vary widely. The influence of light ranged from the north edge of the gap to 12m in the forest, and the southern margin of the gap to 8m in the forest. The edge light of the edge of the gap decreased exponentially with the depth of the forest. The influence of foggy environment in Xishuangbanna on the relative light intensity of the gap and its surroundings can not be ignored. The diurnal variation curve of light transmittance in sunny day was inverted Z shape, and the daily change curve of the relative light intensity at the edge of the gap and the center of the gap was M-shaped, both of which appeared in the morning and evening.