基于连续统去除法的冬小麦叶片全氮含量估算

摘要

以陕西省关中地区冬小麦小区试验为基础,获取不同生育期冬小麦的冠层高光谱数据,提取其连续统去除光谱和7类吸收特征参数,对比原始冠层光谱和连续统去除光谱对叶片氮含量的响应,分析连续统去除光谱吸收特征参数对叶片氮含量的估算能力.结果表明:连续统去除光谱在721 ～ 727 nm波段与叶片氮含量呈极显著负相关,相关系数为-0.851;吸收特征参数增强了对叶片氮含量的估算能力,400 ～ 550 nm波段吸收特征参数与叶片氮含量的相关性弱于550 ～ 770 nm波段;叶片氮含量与550 ～ 770 nm和400 ～ 770 nm的吸收峰总面积、吸收峰左面积以及吸收峰右面积呈显著正相关,与面积归一化最大吸收深度呈显著负相关,且相关系数绝对值均在0.8以上;550 ～ 770 nm波段的吸收峰总面积建立的叶片氮含量指数估算模型精度最高,R2达到0.82,模型检验结果稳定,可用来定量估算冬小麦叶片氮素含量水平.%Based on plot experiments of winter wheat in Guanzhong area of Shaanxi Province,canopy hyper-spectral reflectance data was collected at different winter wheat growth stages.Seven absorption features were calculated based on continuum removed spectra of original canopy spectrum,which were used to explore the quantitative relationship with leaf nitrogen content.The results showed that continuum removed processing enlarged the small differences inherent in original canopy spectra and absorption characteristics controlled by nitrogen stress.The continuum removal spectra obviously improved the correlationship between original canopy reflectance and leaf nitrogen content.It was negatively correlated with leaf nitrogen content in 721 ～ 727 nm with determination coefficient of-0.851.The absorption characteristics parameters improved the leaf nitrogen estimation accuracy compared with sensitive bands,and the estimation accuracy by absorption parameters in 550 ～770 nm performed well than that by the variables in 400 ～550 significantly.Between all the absorption parameters in 550 ～770 nm and 400 ～770 nm bands,the total absorption area,left absorption area,right absorption area and area normalized maximal absorption deep gave more stable achievements than the others,and passed the significant test at P ＜ 0.01 level with absolute value of correlation coefficient over 0.8.The best prediction model was built by total absorption area in 550 ～ 770 nm with determination coefficient of 0.82 with exponential formation.Accuracy test also confirmed the conclusion that the prediction model by total absorption area in 550 ～770 nm was more suitable for estimating the leaf nitrogen content of winter wheat quantificationally.