利用高光谱指数进行冬小麦条锈病严重度的反演研究

Inversion of the severity of winter wheat yellow rust using proper hyper spectral index

通过选取不同条锈病抗性品种(高抗、高感、中间)进行田间不同梯度(对照、轻度、中度、重度)的接种试验,在接种后每隔7d左右,同步测定了不同品种、不同处理的冠层光谱、单叶光谱和对应目标的病情指数以及叶面积指数、叶倾角等生物物理参数和叶绿素、SPAD数值等生物化学参数。通过对获取的光谱数据和生物物理参数和生物化学参数进行统计分析。研究结果表明,小麦被条锈病感染以后,叶片叶绿素含量急剧下降,通过研究叶片绿度值(SPAFD)值与叶绿素含量之间的关系,建立了叶片叶绿素含量和叶片SPAD数值之间的线性关系方程。通过在借鉴前人研究结果的基础上,通过筛选光谱指数,在冠层水平上构建作物冠层结构不敏感色素反演指数(CCII=TCARI/OSAVI)来反演全生育期不同处理的SPAD数值,此反演结果受品种类型、冠层结构和土壤背景的影响较小,线性方程的决定系数达到极显著的水平。在单叶水平选取归一化的光化学指数(NPRI)来反演单叶的病情指数(DI),线性方程的决定系数达到极显著的水平。所以该文通过选取适当的高光谱指数进行冬小麦条锈病严重度的反演的理论和方法是可行的。且反演结果受不同品种、不同叶面积指数和土壤背景等的影响均较小。

The objective of this study was to develop the appropriate spectral indices for prediction of yellow rust index that are relatively insensitive to species, canopy structures (such as leaf area index and leaf angle distributions), foliar inner structures, and soil condition variations. When winter wheat was infected with yellow rust, the leaf chlorophyll concentration decreased, the regression equation between SPAD value and measured chlorophyll concentration was established. Canopy reflected spectrum and canopy chlorophyll concentration were measured during growth duration, it indicated that it had the logarithmic relationship between the ratio of Transformed Chlorophyll Absorption in Reflectance Index (TCARI) to Optimized Soil Adjusted Vegetation Index (OSAVI) and Minolta Chlorophyll Meter (SPAD) value, with a coefficient of determination R2 = 0.7795(n = 320), so the combined index TCARI/OSAVI was proved to be sensitive to chlorophyll concentration and very resistant to the other variations such as Leaf Area Index (LAI) and no photosynthetic materials at canopy level. Therefore, the predictive capability of TCARI/OSAVI seems consistent and satisfactory. The proper reflectance index of photochemical reflectance index (PRI) was chosen for disease index inversion by minimizing foliar inner structure effect, it has linear negative relationship between the normalized photochemical reflectance index (NPRI) and disease index(DI), with a coefficient of determination R2 = 0.8477(n = 63), so the normalized photochemical reflectance index (NPRI) can be used to monitor the disease index of yellow rust.