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为定量评价北京城区绿化人工林叶面积指数LAI变化对改善生态环境效果的影响。2006年4月～2007年3月在北京海淀公园人工林架设涡度相关系统连续观测地表潜热和显热通量,提出LAI-2000实验观测LAI与遥感测量林地面积的加权平均法以估算整个林地LAI,研究LAI季节变化对通量的影响。结果表明:随LAI的增长,潜热占净辐射的比例增加而显热占净辐射的比例减少,具有明显的月变化特征;6～8月LAI>2.0,潜热占净辐射的比例最高,晴天在60%以上,阴天在45%以上,而显热占净辐射的比例最低,晴天低于10%,阴天约5%。12～2月LAI<0.5,潜热占净辐射的比例最低,晴天低于10%,阴晴天的差异很小;显热占净辐射的比例最高,晴天高于40%,而阴天略低于晴天。
In order to quantitatively evaluate the effects of changes of leaf area index (LAI) on the improvement of ecological environment in Beijing urban greening plantations. From April 2006 to March 2007, the surface latent heat and sensible heat fluxes were continuously observed in the erected system of plantations in Haidian Park in Beijing. The LAI-2000 method was used to measure the area of forest land based on LAI and remote sensing. LAI to study the seasonal variation of LAI on the flux. The results show that with the increase of LAI, the ratio of latent heat to net radiation increases and the proportion of sensible heat to net radiation decreases, with obvious monthly variation. LAI> 2.0 from June to August, and latent heat accounts for the highest proportion of net radiation. More than 60%, over cloudy at 45%, while the proportion of sensible heat accounted for the lowest net radiation, sunny less than 10%, cloudy about 5%. From December to February, LAI <0.5, the ratio of latent heat to net radiation was the lowest, less than 10% on sunny days, and very small on cloudy days and sunny days; the ratio of sensible heat to net radiation was the highest, above 40% in sunny days and slightly below sunny day.