Understanding the Impact of Vertical Canopy Position on Leaf Spectra and Traits in an Evergreen Broadleaved Forest
Understanding the Impact of Vertical Canopy Position on Leaf Spectra and Traits in an Evergreen Broadleaved Forest
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DOI：
10.3390/rs13245057
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发表时间：
2021-12
期刊：
影响因子：
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通讯作者：
Fangyuan Yu;T. Gara;Juyu Lian;W. Ye;Jian Shen;Tiejun Wang;Zhi-feng Wu;Junjie Wang
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文献类型：
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作者：
Fangyuan Yu;T. Gara;Juyu Lian;W. Ye;Jian Shen;Tiejun Wang;Zhi-feng Wu;Junjie Wang
研究林冠垂直位置对高大乔木叶片光谱特性的影响，以及利用叶片光谱表征不同林冠位置叶片性状变化的能力的研究较少。利用塔吊采集了亚热带常绿阔叶林下、中、上3个冠层的叶片样本，测定了叶片的8个性状（等效水分厚度、比叶面积、叶片碳含量、叶片氮含量、叶片磷含量、叶片叶绿素含量、类黄酮含量和氮平衡指数）。在全反射光谱范围内，评估了6种植物叶片性状和叶片光谱特性的变异性，以及叶片光谱在3个冠层间跟踪叶片性状变化的能力。结果表明，8个叶片性状在冠层垂直剖面上表现出显著的差异。在垂直树冠剖面上，需光树种（Castanopsis chinensis, Castanopsis fissa，木荷和Machilus chinensis）和耐荫树种（Cryptocarya chinensis和Cryptocarya concinna）的叶片光谱在三个树冠层上呈现出不同的模式。在跟踪叶片叶绿素和黄酮类含量变化方面，冠层下层和上层光谱比中层更为灵敏。研究结果表明，选择合适的冠层是高树野外采样的重要选择，黄酮类化合物是高光谱遥感植物生长制图和监测的重要叶片性状。
Little attention has been paid to the impact of vertical canopy position on the leaf spectral properties of tall trees, and few studies have explored the ability of leaf spectra to characterize the variation of leaf traits across different canopy positions. Using a tower crane, we collected leaf samples from three canopy layers (lower, middle, and upper) and measured eight leaf traits (equivalent water thickness, specific leaf area, leaf carbon content, leaf nitrogen content, leaf phosphorus content, leaf chlorophyll content, flavonoid, and nitrogen balance index) in a subtropical evergreen broadleaved forest. We evaluated the variability of leaf traits and leaf spectral properties, as well as the ability of leaf spectra to track the variation of leaf traits among three canopy layers for six species within the entire reflectance spectrum. The results showed that the eight leaf traits that were moderately or highly correlated with each other showed significant differences along the vertical canopy profile. The three canopy layers of leaf spectra showed contrasting patterns for light-demanding (Castanopsis chinensis, Castanopsis fissa, Schima superba, and Machilus chinensis) and shade-tolerant species (Cryptocarya chinensis and Cryptocarya concinna) along the vertical canopy profile. The spectra at the lower and upper canopy layers were more sensitive than the middle layer for tracking the variation of leaf chlorophyll and flavonoid content. Our results revealed that it is important to choose an appropriate canopy layer for the field sampling of tall trees, and we suggest that flavonoid is an important leaf trait that can be used for mapping and monitoring plant growth with hyperspectral remote sensing.