基于高光谱指数的叶片尺度叶绿素荧光参数反演

在叶片尺度上,基于高光谱植被指数反演实际光合速率(Phi2)、非调节的光能耗散(PhiNO)、非光化学淬灭(PhiNPQ)、相对叶绿素含量(RC)4个叶绿素荧光参数,分析不同氮素处理下叶片光谱反射率和4个叶绿素荧光参数在不同时期的变化特征。结果表明,可见光波段在过量施氮下叶片反射率低于不施氮处理;在近红外波段,叶片光谱反射率随着施氮量的增大而增大。随着玉米的生长,不施氮处理下Phi2逐渐减少,PhiNPQ逐渐增加;过量施氮下Phi2先增加后减少,PhiNO和PhiNPQ先降低后增加。RC在不同施氮条件下均随着生育时期发展先增加后减少。Phi2和PhiNPQ与归一化植被指数(NDVI)的相关性最好,PhiNO与改进型叶绿素吸收比值指数(MCARI)的相关性最好,RC与红边植被指数(CIred edge)的相关性最好。

Retrieval of Leaf-scale Chlorophyll Fluorescence Parameters Based on Hyperspectral Index

In this study, hyperspectral vegetation indices based on leaf scale hyperspectral reflectance were selected to estimate the chlorophyll fluorescence parameters including actual photosynthetic rate(Phi2), non-regulatory energy dissipation(PhiNO), non-photochemical quenching(PhiNPQ), and relative chlorophyll content(RC). Besides, the leaf spectral reflectance and chlorophyll fluorescence parameters dynamic characteristics were analyzed under different nitrogen treatments. The results showed that, with a rise of N treatment rate, spectral reflectance decreased in visible wavelength with increasing N level, opposite trends were found in the near-infrared region. Under zero nitrogen application, the Phi2 decreased with the development of maize growth period, while the PhiNPQ increased with the development of maize growth period. Under the treatment of excessive nitrogen application, the Phi2 increases at the beginning and then decreases, while PhiNO and PhiNPQ decreases firstly and then increases. Under different nitrogen treatments, RC increases firstly and then decreases with the development of the growth period. The Phi2 and PhiNPQ have the best correlation with the normalized difference vegetation index (NDVI), the PhiNO has the best correlation with Modified chlorophyll absorption ratio index (MCARI), and RC has the best correlation with Red edge model(CI_{red edge}).