Yao Fu-qi, Cai Huan-jie, Sun Jin-wei, Qiao Wei
Ying Yong Sheng Tai Xue Bao. 2015 Jul;26(7):2139-45.
By field trials, the canopy hyperspectral reflectance and chlorophyll content (SPAD) for winter wheat during 2010 and 2011 growth periods were measured by the ASD portable spectrometer and portable chlorophyll meter SPAD-502, respectively. The canopy spectral characteristics of different SPAD values were analyzed in different growth periods. The winter wheat SPAD estimation models based on normalized difference vegetation index (NDVI), ratio vegetation index (RVI) and wavelet energy coefficients were established in different growth periods. The results showed that green peak and red valley characteristics became more and more obvious with the increase of the SPAD. The SPAD estimation models based on NDVI performed better at the regreening stage, elongation stage, heading stage and filling stage with determination coefficients (R2) being 0.7957, 0.8096, 0.7557 and 0.5033, respectively. The winter wheat SPAD estimation models based on wavelet energy coefficients could greatly improve the SPAD estimation accuracy, with regression determination coefficients (R2) of the PVC estimation models based on high frequency energy coefficient and low frequency energy coefficient being 0.9168, 0.9154, 0.8802 and 0.9087 at the regreening stage, elongation stage, heading stage and filling stage, respectively.
通过田间试验，分别于2010年和2011年小麦生育期，使用ASD便携式光谱仪和便携式叶绿素仪SPAD - 502测量了冬小麦冠层的高光谱反射率和叶绿素含量（SPAD值）。分析了不同生育期不同SPAD值的冠层光谱特征。建立了不同生育期基于归一化植被指数（NDVI）、比值植被指数（RVI）和小波能量系数的冬小麦SPAD估算模型。结果表明，随着SPAD值的增加，绿峰和红谷特征越来越明显。基于NDVI的SPAD估算模型在返青期、拔节期、抽穗期和灌浆期表现较好，决定系数（R2）分别为0.7957、0.8096、0.7557和0.5033。基于小波能量系数的冬小麦SPAD估算模型能大幅提高SPAD估算精度，基于高频能量系数和低频能量系数的PVC估算模型在返青期、拔节期、抽穗期和灌浆期的回归决定系数（R2）分别为0.9168、0.9154、0.8802和0.9087。
