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A comparison of different methods for assessing leaf area index in four canopy types

机译：四个冠层类型评估叶面积指数的不同方法的比较

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摘要

The agreement of Leaf Area Index (LAI) assessments from three indirect methods, i.e. the LAIa??2200 Plant Canopy Analyzer, the SS1 SunScan Canopy Analysis System and Digital Hemispherical Photography (DHP) was evaluated for four canopy types, i.e. a short rotation coppice plantation (SRC) with poplar, a Scots pine stand, a Pedunculate oak stand and a maize field. In the SRC and in the maize field, the indirect measurements were compared with direct measurements (litter fall and harvesting). In the low LAI range (0 to 2) the discrepancies of the SS1 were partly explained by the inability to properly account for clumping and the uncertainty of the ellipsoidal leaf angle distribution parameter. The higher values for SS1 in the medium (2 to 6) to high (6 to 8) ranges might be explained by gap fraction saturation for LAIa??2200 and DHP above certain values. Wood area index a??understood as the woody light-blocking elements from the canopy with respect to diameter growtha?? accounted for overestimation by all indirect methods when compared to direct methods in the SRC. The inter-comparison of the three indirect methods in the four canopy types showed a general agreement for all methods in the medium LAI range (2 to 6). LAIa??2200 and DHP revealed the best agreement among the indirect methods along the entire range of LAI (0 to 8) in all canopy types. SS1 showed some discrepancies with the LAIa??2200 and DHP at low (0 to 2) and high ranges of LAI (6 to 8).
机译：三种间接方法的叶面积指数（LAI）评估协议，即LAIA ?? 2200植物冠层分析仪，SS1 Sunscan Canopy分析系统和数字半球摄影（DHP）进行了四种冠层类型，即短旋转Coppice种植园（SRC）与杨树，苏格兰松树架，虎橡胶支架和玉米田。在SRC和玉米场中，将间接测量与直接测量（垃圾衰落和收获）进行比较。在低LAI范围（0至2）中，SS1的差异部分地解释了无法正确考虑块状和椭圆形叶角分布参数的不确定性。介质（2至6）中的SS1的较高值（2至8）范围可以通过Laia的间隙分数饱和度和DHP高于某些值来解释。木地区指数a ??被理解为从冠层的木质遮光元件相对于直径增长？与SRC中的直接方法相比，所有间接方法都会占用。四种间接方法中三种间接方法的相互比较显示了介质莱范围内所有方法的一般协议（2至6）。 Laia ?? 2200和DHP在所有冠层类型中展示了沿着莱莱（0至8）的整个范围的间接方法之间的最佳协议。 SS1显示了Laia ?? 2200和DHP的一些差异，低（0到2）和Lai的高范围（6至8）。

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