青海大通地区退耕地人工林分的消光特性

 通过对青海省大通县退耕还林后现存人工林群落2004年5—7月典型晴天净辐射在林冠内垂直分布的实测资料分析,研究青海云杉林、华北落叶松林、中国沙棘林、白桦林和青杨林5种林分类型的消光特性。根据BeerLambert方程,结合林分生长季内的叶面积指数动态变化,对5种林分日内不同时刻消光系数、日内最小消光系数、典型天的日均消光系数和不同林冠深度的叶面积指数及其对应的消光能力变化做了研究。结果表明:日均消光系数与日内最小消光系数和叶面积指数相关性显著,并拟合出相应的关系表达式;各林分不同林冠深度的叶面积指数累积分布变化曲线均呈“S”型;华北落叶松林和青海云杉林冠2/3以上的中上部冠层消光能力明显高于下层,而白桦林和青杨林垂直消光能力各层差异不明显。

Extinction characteristics of artificial forest in removal lands in Datong of Qinghai province

Based on the observed data of net radiation（Rn）'s distribution of typical sunny day in the canopy in artificial forest community which existed after removing lands from cultivation to afforestation and grassland in Datong county from May to July,the extinction characteristics of the communities of Picea crassifolia,Larix principis-rupp rechtii,Hippohae rha mnoides ssp.Sinensis,Betula platyphylla and Populus cathayana were studied.According to Beer Lambert' equation and considering the dynamic variation of the leaf areas index in the growing season of forest,the daily extinction coefficient in different time,daily minimum extinction coefficient and the daily mean extinction coefficient of typical day were studied.Some researches in the variation of leaf areas index and extinction capacity of different canopy depths in different communities were also done.The results showed that the correlation between daily mean extinction coefficient & minimum extinction coefficient and leaf areas index is obvious and equation was simulated.In different canopy depths of all forests,the（cumulative） distribution curves of leaf areas index were S-shape;the extinction capacity above two thirds of the canopy of the Larix principis-rupp rechtii and Picea crassifolia is higher distinctly than he lower,but the variance of Betula platyphylla and Populus cathayana is not obvious.