The effect of plant phenology and canopy structure of four crops and four weed species on reflectance spectra were evaluated in 2016 and 2017 using in situ spectroscopy. Leaf-level and canopy-level reflectance were collected at multiple phenologic time points in each growing season. Reflectance values at 2 wk after planting (WAP) in both years indicated strong spectral differences between species across the visible (VIS; 350–700 nm), near-infrared (NIR; 701–1,300 nm), shortwave-infrared I (SWIR1; 1,301–1,900 nm), and shortwave-infrared II (SWIR2; 1,901–2,500 nm) regions. Results from this study indicate that plant spectral reflectance changes with plant phenology and is influenced by plant biophysical characteristics. Canopy-level differences were detected in both years across all dates except for 1 WAP in 2017. Species with similar canopy types (e.g., broadleaf prostrate, broadleaf erect, or grass/sedge) were more readily discriminated from species with different canopy types. Asynchronous phenology between species also resulted in spectral differences between species. SWIR1 and SWIR2 wavelengths are often not included in multispectral sensors but should be considered for species differentiation. Results from this research indicate that wavelengths in SWIR1 and SWIR2 in conjunction with VIS and NIR reflectance can provide differentiation across plant phenologies and, therefore should be considered for use in future sensor technologies for species differentiation.

中文翻译：

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物候利用高光谱遥感影响作物和杂草物种的分化

2016 年和 2017 年使用原位光谱评估了四种作物和四种杂草的植物物候和冠层结构对反射光谱的影响。在每个生长季节的多个物候时间点收集叶级和冠层级反射率。两年种植后 2 周的反射率值 (WAP) 表明物种之间在可见光（VIS；350–700 nm）、近红外（NIR；701–1,300 nm）、短波红外 I（SWIR1； 1,301–1,900 nm）和短波红外 II（SWIR2；1,901–2,500 nm）区域。这项研究的结果表明，植物光谱反射率随植物物候而变化，并受植物生物物理特性的影响。除 2017 年的 1 个 WAP 外，所有日期在这两年都检测到冠层水平差异。具有相似冠层类型（例如，阔叶匍匐、阔叶直立或草/莎草）的物种更容易与具有不同冠层类型的物种区分开来。物种之间的异步物候也导致物种之间的光谱差异。SWIR1 和 SWIR2 波长通常不包括在多光谱传感器中，但应考虑用于物种区分。这项研究的结果表明，SWIR1 和 SWIR2 中的波长与 VIS 和 NIR 反射率相结合可以提供跨植物物候的区分，因此应考虑在未来的传感器技术中用于物种分化。物种之间的异步物候也导致物种之间的光谱差异。SWIR1 和 SWIR2 波长通常不包括在多光谱传感器中，但应考虑用于物种区分。这项研究的结果表明，SWIR1 和 SWIR2 中的波长与 VIS 和 NIR 反射率相结合可以提供跨植物物候的区分，因此应考虑在未来的传感器技术中用于物种分化。物种之间的异步物候也导致物种之间的光谱差异。SWIR1 和 SWIR2 波长通常不包括在多光谱传感器中，但应考虑用于物种区分。这项研究的结果表明，SWIR1 和 SWIR2 中的波长与 VIS 和 NIR 反射率相结合可以提供跨植物物候的区分，因此应考虑在未来的传感器技术中用于物种分化。