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首页> 外文期刊>International journal of applied earth observation and geoinformation >Detecting leaf-water content in Mediterranean trees using high-resolution spectrometry
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Detecting leaf-water content in Mediterranean trees using high-resolution spectrometry

机译：使用高分辨率光谱法检测地中海树木中的叶水含量

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Water content of the vegetation canopy or individual leaves is an important variable in physiological plant processes. In Mediterranean regions where water availability is an important production limiting factor, it is a strong indicator of vegetation stress. Spectroscopic earth-observation techniques in the solar part of the electromagnetic spectrum provide opportunities to determine leaf and canopy-water content due to the presence of water-absorption bands around 970 and 1200nm. We investigated the possibilities to predict leaf-water content of three dominant tree species in a study area in Mediterranean France using spectral indices. During a field campaign leaf-water content (EWT) was determined and high-resolution spectra were measured of the same leaves. The spectra were measured in two ways: using an optical cable with a field of view of 25° and using a leaf clip with its own artificial illumination source. The spectra were analyzed and related to leaf-water content as original reflectance spectra and as continuum-removed spectra using eight spectral leaf-water indices. Next, reflectance spectra were simulated to explore their sensitivity to environmental conditions like leaf area index and illumination angle using a radiative transfer model. Results show that a good correlation (0.70) exists between leaf-water content and spectral indices using the right slope of the 970 nm water-absorption band. Continuum-removal correction of the spectra improved the relations. The model sensitivity analysis illustrated that from a set of five environmental variables leaf area index has, as may be expected, an important impact on leaf-water estimates. This field and model study illustrates that it is feasible to determine foliar water content on the basis of spectral indices located around the minor water-absorption bands with a limited effect of environmental conditions.
机译：植被冠层或单叶的水分含量是生理植物过程中的重要变量。在地中海地区，水的可用性是重要的生产限制因素，它是植被压力的有力指标。由于存在970和1200nm左右的吸水带，电磁光谱太阳能部分的光谱地球观测技术为确定叶片和冠层水含量提供了机会。我们调查了使用光谱指数预测法国地中海研究区域中三种优势树种的叶水含量的可能性。在田间运动期间，确定了叶片的水分含量（EWT），并测量了相同叶片的高分辨率光谱。通过两种方式测量光谱：使用视线为25°的光缆以及使用带有其自己的人工照明源的叶夹。使用八种光谱叶水指数对光谱进行分析，并将其与叶水含量相关，作为原始反射光谱和去除连续谱的光谱。接下来，使用辐射转移模型模拟反射光谱以探索其对环境条件（如叶面积指数和照明角度）的敏感性。结果表明，使用970 nm吸水带的右斜率，叶片含水量与光谱指数之间存在良好的相关性（0.70）。光谱的连续去除校正改善了这种关系。模型敏感性分析表明，如预期的那样，从五个环境变量集中，叶面积指数对叶水估计值具有重要影响。该领域和模型研究表明，在环境条件影响有限的情况下，根据次要吸水带周围的光谱指数确定叶面含水量是可行的。

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