Li Yingxue, Zhu Yan, Dai Tingbo, Tian Yongchao, Cao Weixing
Hi-Tech Key Laboratory of Information Agriculture of Jiangsu Province, Key Laboratory of Crop Growth Regulation of Agriculture Ministry, Nanjing Agricultural University, Nanjing 210095, China.
Ying Yong Sheng Tai Xue Bao. 2006 Aug;17(8):1443-7.
Based on the change patterns of leaf area index (LAI) and canopy spectral reflectance of wheat at different growth stages and nitrogen application rates, this paper investigated the relationships of LAI with canopy reflectance and spectral parameters, and brought forward the sensitive spectral parameters and quantitative equation for predicting wheat LAI. The results showed that with increasing nitrogen application rate, wheat LAI and its canopy reflectance at near infrared (760 to approximately 1220 nm) increased, whereas the reflectance at visible band (460 to approximately 710 nm) decreased. From jointing to maturity, the LAI and the reflectance of short bands in near infrared increased initially and decreased then, whereas the reflectance of visible light and long bands in near infrared was in adverse, with the lowest value appeared at booting stage. Wheat LAI was negatively correlated with the reflectance of visible light, but positively with that of short bands in near infrared, with the highest correlation coefficient at 810 nm. It was proposed that wheat LAI could be well monitored by vegetation indices RVI (810, 510) and DVI (810, 560). PVI and TSAVI were proved to be the spectral indices in monitoring wheat LAI, and higher accuracy was obtained with combined RVI (810, 510), DVI (810, 560) and PVI.
基于不同生长阶段和施氮量下小麦叶面积指数（LAI）和冠层光谱反射率的变化模式，本文研究了LAI与冠层反射率及光谱参数之间的关系，提出了预测小麦LAI的敏感光谱参数和定量方程。结果表明，随着施氮量的增加，小麦LAI及其近红外波段（760至约1220nm）的冠层反射率增加，而可见光波段（460至约710nm）的反射率降低。从拔节期到成熟期，LAI和近红外短波段反射率先增加后降低，而可见光和近红外长波段反射率则相反，在孕穗期出现最低值。小麦LAI与可见光反射率呈负相关，与近红外短波段反射率呈正相关，在810nm处相关系数最高。提出利用植被指数RVI（810,510）和DVI（8,10,560）可以很好地监测小麦LAI。PVI和TSAVI被证明是监测小麦LAI的光谱指数，结合RVI（810,510）、DVI（810,560）和PVI可获得更高的精度。
