Impacts of Leaf Age on Canopy Spectral Signature Variation in Evergreen Chinese Fir Forests
Impacts of Leaf Age on Canopy Spectral Signature Variation in Evergreen Chinese Fir Forests
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DOI：
10.3390/rs10020262
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发表时间：
2018-02
期刊：
影响因子：
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通讯作者：
Qiaoli Wu;C. Song;Jinling Song;Jindi Wang;Shaoyuan Chen;Bo Yu
中科院分区：
文献类型：
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作者：
Qiaoli Wu;C. Song;Jinling Song;Jindi Wang;Shaoyuan Chen;Bo Yu
我们对叶片老化对冠层信号变异影响的了解存在重大差距，这限制了我们基于遥感数据对植被状况的理解。为了了解叶子老化对叶子和冠层尺度的影响，采用了实地、遥感和物理建模技术相结合的方法来评估常绿杉木森林的冠层光谱信号。我们观察到，从 5 月到 10 月，新叶的近红外 (NIR) 反射率增加了约 10%，成熟叶的 NIR 透射率增加了 35%。当仅考虑成熟叶片或新叶和成熟叶片的叶片光学特性（LOP）变化时，几何光学和辐射传输（GORT）模型模拟的冠层反射率轨迹与Landsat观测结果更加一致（NIR反射率的R2从0.37增加到0.82~0.89，EVI2从0.35增加到0.67~0.88，RMSE较小（0.01到0.01） 0.02））。这项研究强调了叶龄对叶子光谱特征的重要性，并提供了年龄依赖性 LOP 的证据，这些 LOP 对 NIR 波段和 EVI2 的冠层反射率有重要影响，用于监测冠层动态和生产力，对 RS 和森林生态系统生态学具有重要意义。
Significant gaps exist in our knowledge of the impact of leaf aging on canopy signal variability, which limits our understanding of vegetation status based on remotely sensed data. To understand the effects of leaf aging at the leaf and canopy scales, a combination of field, remote-sensing and physical modeling techniques was adopted to assess the canopy spectral signals of evergreen Cunninghamia forests. We observed an approximately 10% increase in Near-Infrared (NIR) reflectance for new leaves and a 35% increase in NIR transmittance for mature leaves from May to October. When variations in leaf optical properties (LOPs) of only mature leaves, or both new and mature leaves were considered, the Geometric Optical and Radiative Transfer (GORT) model-simulated canopy reflectance trajectory was more consistent with Landsat observations (R2 increased from 0.37 to 0.82~0.89 for NIR reflectance, and from 0.35 to 0.67~0.88 for EVI2, with a small RMSE (0.01 to 0.02)). This study highlights the importance of leaf age on leaf spectral signatures, and provides evidence of age-dependent LOPs that have important impacts on canopy reflectance in the NIR band and EVI2, which are used to monitor canopy dynamics and productivity, with important implications for RS and forest ecosystem ecology.