Validity of surface area indices of Pinus radiata estimated from transmittance of the sun's beam
Validity of surface area indices of Pinus radiata estimated from transmittance of the sun's beam
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DOI：
10.1016/0168-1923(91)90084-4
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发表时间：
1991-12
影响因子：
6.2
通讯作者：
A. Lang;R. McMurtrie;M. Benson
中科院分区：
文献类型：
--
作者：
A. Lang;R. McMurtrie;M. Benson
森林的总表面积指数可以利用太阳直射光束的透过率来估算。通常，透射率在一个区域或一条线上线性平均，并根据该透射率的平均值估计表面积指数。然而，如果植被是丛生的或行与行之间有间隙，则表面积指数的值较低。在这种情况下，建议采用这样一种程序，即先在小距离上线性求平均值，然后再对数求平均值。这种方法给出了辐射松人工林的表面积指数的估计值，该指数是由生物量和针叶比表面积测量得到的总表面积指数的88%或76%。另一方面，对于相同的比较，透过率的线性平均值给出了表面积指数的值，分别是直接测量的65%和56%。
Total surface area indices of forests can be estimated using the transmittance of the direct beam of the sun. Usually, the transmittance is averaged linearly over an area or a line and the surface area index is estimated from this average of the transmittance. However, low values are obtained for surface area indices if the vegetation is clumped or has gaps between rows. In such cases, a procedure is recommended in which the averaging is carried out linearly over a small distance and then logarithmically. It is argued that this correctly accounts for gross discontinuities in canopies.This method gave estimates of surface area indices in a plantation ofPinus radiatawhich were 88% of the needle or 76% of the total surface area indices obtained from biomass and specific surface area measurements of needles. On the other hand, for the same comparisons, linear averages of the transmittance give values of the surface area indices which were 65% and 56% of the direct measurements, respectively.