琅琊山景区不同叶绿素条件下树种叶片光谱差异分析

叶绿素含量高低反映植物健康状况，研究景区树种叶片叶绿素绝对值(SPAD)不同的光谱变化规律能为叶绿素高光谱监测波段识别与景区树种管理提供理论支撑。从琅琊山景区灌木和乔木类选取9个常见树种，探讨相同树种叶片SPAD值变化时的光谱差异，同时，横向对比相同SPAD值不同树种叶片的光谱特征，并深入分析不同树种叶片SPAD值与单波段原始光谱、光谱倒数、一阶微分、二阶微分及波段组合差值指数、归一化指数、比值指数、一阶微分归一化指数、一阶微分比值指数之间的关系。结果表明：9个所测树种叶片随着叶绿素SPAD值的升高，光谱变化规律各不相同，在可见光波段区分明显，总体上，光谱反射率最高的样本组SPAD值较低；叶绿素SPAD值相同时，在可见光波段，桂花较其余树种反射率整体较高; 在780~1 350 nm波段，广玉兰叶片反射率始终排前三，其余波段变化规律不明显；原始光谱反射率的二阶微分与海桐叶片SPAD值相关系数最大，一阶微分与其余8种相关性最高；与灌木、落叶乔木叶片SPAD值相关系数最大的光谱指数分别为差值指数、一阶微分归一化指数，与常绿乔木、不分树种相关系数最大的为一阶微分比值指数。

Spectral Differences of Tree Leaves at Different Chlorophyll Relative Content in Langya Mountain

Chlorophyll content reflects plant health status. Studying on spectral characteristics and regularity of tree leaves at different SPAD values can provide theoretical support for band recognition of chlorophyll hyperspectral monitoring and trees species health management. Nine tree species from shrub and arbor in Langya Mountain scenic spots were selected to explore the spectral characteristics of the same tree species with the SPAD values changing and the spectral differences of different tree species with the same SPAD values in this paper. At the same time, the relationship between different tree leaves chlorophyll content (SPAD) and the original spectrum, the inverse of the spectrum, the first order differential of the spectrum, the second order differential of the spectrum and the various band combinations of the spectrum such as difference index, normalization vegetation index, ratio index, first order differential normalization vegetation index, first order differential ratio index were discussed in depth. The results showed that the spectral characteristics of nine kinds of tree species leaves were distinct with the SPAD values changing, and the distinction was evident in the visible band, in general, the leaves SPAD values with the highest spectral reflectance was lower. In addition, the spectral reflectance of osmanthus leaves was higher than that of the other species in the visible band, and the spectral reflectance of Magnolia grandiflora leaves was always the first three in 780~1 350 nm band when the chlorophyll SPAD value was the same, but the changing law was not obvious in other bands. Moreover, the second order differential of the original spectrum had the highest correlation coefficient with the SPAD value of Pittosporum leaves, as the first order differential had the highest correlation with the others. The spectral indices with the highest correlation coefficient of SPAD value of shrubs and deciduous tree leaves were differential index and normalized vegetation index of first order differential of the spectrum, otherwise, evergreen trees and trees regardless of species were of the highest correlation coefficient with ratio index of the first order differential of the spectrum.