中文摘要：

应用Li-cor LAI-2000植物冠层分析仪,研究生长季节川西亚高山暗针叶林叶面积指数（LAI）的时间动态,比较4种岷江冷杉林分LAI的差异性,分析LAI与海拔和坡向之间的关系,探讨林分尺度和小流域尺度上LAI的空间变异性。结果表明：川西亚高山暗针叶林小流域LAI的季节动态变化规律明显,为单峰曲线,峰值（5.82±1.32）出现在8月中旬;4种岷江冷杉林LAI平均值为5.44±0.83,不同林分之间LAI差异极显著（p〈0.001）,LAI顺序为：藓类-箭竹-岷江冷杉林〉草类-箭竹-岷江冷杉林〉草类-杜鹃-岷江冷杉林〉藓类-杜鹃-岷江冷杉林;随着海拔升高,LAI先增加,后减小,转折点出现在海拔3000m处,LAI（y）与海拔（x）之间的回归方程为：y=-22.4086＋0.0196x-0.0000033601x^2（R^2=0.9996,p〈0.001,n=12）;半阴坡LAI（5.51±0.91）比半阳坡（5.36±0.72）大,差异显著（p〈0.05）;林分尺度上的LAI变异系数（10.02%～12.22%）约是小流域尺度上的（19.79%～22.80%）1/2,随着海拔升高,其变化比较复杂,3800m处最大（23.09%）,3500m处最小（7.64%）,且半阴坡（16.58%）〉半阳坡（13.44%）。

英文摘要：

Field surveys have been conducted by using a Li-cor LAI-2000 plant canopy analyzer in a small sub-alpine dark coniferous forested catchment in western Sichuan Province during the period from July to September,2005.This study is to quantify LAI of the four different fir stands composed mainly of Abies faxoniana and LAI seasonal patterns,and to explore the relationship between LAI and topographical factors in terms of altitude and aspects,and spatial variability of LAI at catchment scale and at stand scale.The results showed that single peak curve of LAI seasonal change pattern occurred in sub-alpine dark coniferous forest during growing season,with the peak value of 5.82±1.32 in the middle ten days of August.There were significant differences in LAI among the four stands（p〈0.001）,with the mean LAI value of 5.44±0.83.The highest LAI occurred in the moss,Fargesia nitida,Bashania fangiana and A.faxoniana stand,followed by the grass,F.nitida,B.fangiana and A.faxoniana stand and the grass,Rhododendron spp.and A.faxoniana stand,while the lowest LAI value was in the moss,Rhododendron spp.and A.faxoniana stand.With increasing altitude,LAI increased subtly at first,but then decreased continuously when the elevation exceeded 3 000 m.The relationship between LAI（y）and altitude（x）can be commendably expressed as the following regression equation：y=-22.408 6＋0.019 6x-0.000 003 360 1x^2（R 2= 0.999 6,p〈0.001,n=12）.LAI at northeast-aspect was larger than that at southwest-aspect,with the significant difference in LAI between the two aspects（p〈0.05）.The coefficient of variability（CV）of LAI at catchment scale（19.79%～22.80%）was approximately twice larger as that at stand scale（10.02%～12.22%）.At the different altitudinal gradients,the highest CV（23.09%）was at the elevation of 3 800 m,while the lowest（7.64%）was at 3 500 m.The CV at northeast-aspect（16.58%）was higher than that at southwest-aspect（13.44%）.