关中地区夏玉米抽穗期叶绿素含量的高光谱估算

目的]利用高光谱数据进行叶绿素估算,为快速获取作物的生长信息、生长诊断及精确管理提供依据。方法]基于陕西省关中地区抽穗期夏玉米冠层光谱特征及叶绿素含量的测定,运用线性及非线性分析方法建立了基于原始光谱敏感波段和一阶微分光谱敏感波段叶绿素估算模型。结果]夏玉米抽穗期反射光谱在可见光及中远红外区域,叶绿素含量越高,光谱曲线越向下偏移;在红边区域,叶绿素含量对光谱曲线影响不显著;在近红外波段,叶绿素含量越高,光谱曲线越向上偏移。基于一阶微分光谱敏感波段的夏玉米叶绿素含量估算模型拟合精度要优于基于原始光谱敏感波段估算模型,决定系数R2分别为0.81和0.60,均方根误差(RMSE)分别为2.39,4.41。结论]基于一阶微分光谱敏感波段建模分析是估测抽穗期夏玉米冠层叶绿素含量的重要方法,对指导西北地区夏玉米种植与生产具有积极的借鉴意义。

Hyperspectral Estimation of Canopy Chlorophyll Content in Summer Corn in Guanzhong Area

Objective] Hyperspectral estimation of canopy chlorophyll content was expected to provide a clue for obtaining growth information rapidly, diagnosing growth situation and precision management of crops. Methods] Based on the measurement of canopy spectral characteristics and chlorophyll content of summer corn in heading stage in Guanzhong area of Shaanxi Province, a model with regard to the canopy chlorophyll content estimation was established by relating the original spectrum and the first derivative spectral reflectance of sensitive band. Results] For the reflection spectral of corn in the heading stage, the spectral curve showed downward trend with the increase of chlorophyll content in the visible and infrared band; influence of chlorophyll content on spectral curve in the red edge band was not obvious, and the spectral curve showed upward trend with the increase of chlorophyll content in the near infrared band. Fitting precision of the estimation model with the sensitive band of the first derivative spectral reflectance were superior to the original spectral reflectance. The coefficients of determination R² of the model based on the first derivative spectral and the original spectral reflectance were 0.81 and 0.60, the root mean square errors(RMSE) were 2.39 and 4.41 respectively. Conclusion] The sensitive bands of first derivative spectral reflectance was an important indexes for canopy chlorophyll content estimation of summer corn in heading stage. The models have positive significance to guide the plantation and the production for summer corn in the northwest of China.