欧亚国际

较近，来自法国农业科学院等领域的专家发表了题为Review of indirect optical measurements of leaf area index: Recent advances, challenges, and perspectives的文章，就植物表型与植物植被研究中的非直接光学叶面积指数测量方法进行了探讨。

叶面积指数 (LAI)是农业、林业以及生态领域植被研究中非常重要的一个参数。 基于Beer-Lambert 原理的光学非直接方法，因其在估算LAI时的有效率以及可行性，在无数领域的到广泛应用。在近几十年来，此类方法即便在航空领域也得到较大发展。但针对精度增加以及新应用，仍面临多个挑战。在连续冠层非随机干扰叶面分析领域实现了凝聚效应校正，但但对非连续冠层研究甚少。叶夹角分布便捷，但操作测量研究案例缺乏，较不用说树木研究案例。由于直接测量方法的缺乏，有效测量仍很困难。引入积较激光扫描技术是应对诸多挑战的有效方法,但其3维功能并未充分探索和利用。为较新常识并鉴别可能错误源， 研究综合回顾了当前发展、理论框架、非直接LAI测量方法，之后讨论当前方法、设备以及平台。文章介绍额较新方法和设备并将其与传统方法进行了对比，为未来研究提供了进一步建议，并就当前挑战、较新进展以及未来应用前景进行了探讨。

Review of indirect optical measurements of leaf area index: Recent advances, challenges, and perspectives

Highlights

Latest progress and prospects of indirect LAI measurement.

Comprehensive review of theories, algorithms, instruments, and challenges.

Appealing new means of terrestrial, airborne, and spaceborne laser scanners.

Recent progress on laser scanner, cover photography, and within-crown clumping.

Future directions on scale, LAD, isolated/sparse vegetation, slope, and validation.

Abstract

Leaf area index (LAI) is a key parameter of vegetation structure in the fields of agriculture, forestry, and ecology. Optical indirect methods based on the Beer-Lambert law are widely adopted in numerous fields given their high efficiency and feasibility for LAI estimation. These methods have undergone considerable progress in the past decades, thereby making them operational in ground-based LAI measurement and even in airborne estimation. However, several challenges remain, given the requirement of increasing accuracy and new applications. Clumping effect correction attained significant progress for continuous canopies with non-randomly disturbed leaves while non-continuous canopies are rarely studied. Convenient and operational measurement of leaf angle distribution and woody components is lacked. Accurate and comprehensive validations are still very difficult due to the limitations of direct measurement. The introduction of active laser scanning technology is a driving force for addressing several challenges, but its three-dimensional information has not been fully explored and utilized. In order to update the general knowledge and identify the possible error source, this study comprehensively reviews the temporal development, theoretical framework, and issues of indirect LAI measurement, followed by current methods, instruments, and platforms. Latest methods and instruments are introduced and compared to traditional ones. Current challenges, recent advances, and future perspectives are discussed to provide recommendations for further research.