The potential of dual-wavelength laser scanning for estimating vegetation moisture content
The potential of dual-wavelength laser scanning for estimating vegetation moisture content
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DOI：
10.1016/j.rse.2013.01.001
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发表时间：
2013-05-15
影响因子：
13.5
通讯作者：
Gunawan, O.
中科院分区：
文献类型：
--
作者：
Gaulton, R.;Danson, F. M.;Gunawan, O.
植被含水率是森林干旱胁迫、病害和火灾风险的重要早期指标。现有的测量植被生物化学特性的遥感技术，如等效水厚度(EWT)，由于不能区分树冠和林下植物的特性而受到限制，并且受到树冠结构变化的影响。通过提供距离分辨的反射率估计，激光扫描仪测量有可能克服这些限制。双波长激光扫描可以提供对反射率的主动测量，由此可以得出光谱指数，这些光谱指数对激光光束内目标的距离、入射角和散射面积不敏感，这些因素使得利用单波长激光扫描仪强度数据变得困难。本研究通过确定使用近红外(1063 Nm)和中红外(1545 Nm)波长的激光扫描仪得出的光谱指数与单个叶片的EWT之间的关系，证明了双波长激光扫描在测量叶片生化特性方面的潜力。使用叶片光学特性模型(PROSPECT-5)测试了该指数的适用性和灵敏度，并使用索尔福德高级激光冠层分析仪在实验室条件下对该方法进行了实验测试。这两个波长的归一化比值与叶片样品的EWT之间存在很强的相关性(R2=0.8RMSE=0.0069 GCM(-2))。这种关系与模型预测的结果吻合得很好。然而，实验数据也显示了个体叶片上指标值的显著空间变异性，这表明叶片内尺度上的水分分布是不均匀的。这项研究表明，使用双波长和多光谱激光扫描来测量植被的生化特性具有巨大的潜力。(C)2013 Elsevier Inc.保留所有权利。
Vegetation moisture content is an important early indicator of forest drought stress, disease and fire risk. Existing remote sensing techniques to measure biochemical properties of vegetation, such as Equivalent Water Thickness (EWT), are limited by an inability to differentiate canopy and understorey properties and are influenced by variations in canopy structure. By providing a range-resolved estimate of reflectance, laser scanner measurements have the potential to overcome these limitations. Dual-wavelength laser scanning can provide an active measurement of reflectance from which spectral indices can be derived that are insensitive to range, incidence angle and scattering area of the target within the laser beam, factors that make exploiting single-wavelength laser scanner intensity data difficult.This study demonstrates the potential of dual-wavelength laser scanning for measurement of leaf biochemical properties, through determining the relationship between a laser-scanner-derived spectral index, using near infrared (1063 nm) and middle infrared (1545 nm) wavelengths, and the EWT of individual leaves. The suitability and sensitivity of the index is tested using a leaf optical properties model (PROSPECT-5) and the method is tested experimentally under laboratory conditions using the Salford Advanced Laser Canopy Analyser. A strong relationship (R-2=0.8, RMSE=0.0069 gcm(-2)) was found between a normalised ratio of the two wavelengths and measured EWT of leaf samples. The relationship corresponds well to that predicted by modelling. However, the experimental data also revealed significant spatial variability in the index value across individual leaves, suggesting heterogeneity in moisture distribution at within-leaf scales. The study suggests significant potential for using dual-wavelength and multispectral laser scanning for measuring-vegetation biochemical properties. (C) 2013 Elsevier Inc. All rights reserved.