Estimation of leaf water content and specific leaf weight from reflectance and transmittance measurements
Estimation of leaf water content and specific leaf weight from reflectance and transmittance measurements
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DOI：
10.1051/agro:19970903
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发表时间：
1997-11-01
期刊：
影响因子：
--
通讯作者：
Fourty, T
中科院分区：
文献类型：
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作者：
Baret, F;Fourty, T
利用鲜叶的广泛变化来估计水分和干物质的比吸收系数。这些系数来自前景叶片光学特性模型的反演，使用在1300-2400 nm范围内测量的反射率和透射率光谱以及相应的含水量（g. cm（-2））和比叶重（每单位叶面积的干物质质量，g.cm（-2））。结果表明，干物质的比吸收系数的估计值是不可靠的，在强吸水带，虽然有协议与以前的研究在光谱区域，水贡献适度叶吸收。因此，我们建议使用Fourty等人（1996）推导的干叶干物质比吸收系数值。水的比吸收系数的估计值略高于Curcio和Petty（1951）提出的纯水的值。然后，我们研究了通过反演前景模型来估计叶片含水量和比重的可能性，该模型同时或分别使用在新鲜叶片上测量的反射和/或透射光谱以及Fourty等人（1996）提出的干物质的比吸收系数，以及Curcio和Petty（1951）提出的水的比吸收系数。在训练数据集和独立数据集上获得的结果显示，当同时使用反射率和透射率时，水分含量（RMSE = 0.0025g.cm（-2））和比叶重（RMSE = 0.0016 g.cm（-2））的估计值准确且稳健。当使用反射率或透射率测量时，由于反演过程中约束条件的放松，水分和干物质含量估计的性能下降。这些结果的可能应用进行了讨论。
Specific absorption coefficients for water and dry matter were estimated using a wide range of variation of fresh leaves. The coefficients were derived from the inversion of the PROSPECT leaf optical property model using reflectance and transmittance spectra measured over the 1300-2400-nm domain and the corresponding water content (g.cm(-2)) and specific leaf weight (mass of dry matter per unit leaf.area, g.cm(-2)). Results show that the estimated values of the specific absorption coefficient for dry matter were not reliable in the strong water absorption bands, although there was agreement with previous studies in spectral regions where water contributed moderately to leaf absorption. We thus proposed to use the values derived by Fourty et al (1996) for dry leaves for the specific absorption coefficient of dry matter. Estimated values of the specific absorption coefficient of water were slightly higher than the values proposed by Curcio and Petty (1951) for pure water. We then investigated the possibility of estimating leaf water content and specific weight by inverting the PROSPECT model using concurrently or separately reflectance and/or transmittance spectra measured over fresh leaves and the specific absorption coefficients proposed by Fourty et al (1996) for dry matter, and Curcio and Petty (1951) for water. Results obtained on the training data set and on an independent data set show accurate and robust estimates of both water content (RMSE = 0.0025 g.cm(-2)) and specific leaf weight (RMSE = 0.0016 g.cm(-2)) when reflectance and transmittance were used concurrently. When either reflectance or transmittance measurements were used, the performances of water and dry matter content estimation decreased because of the relaxation of constraints in the inversion process. Possible applications of these results are discussed.