Yellow flowers can decrease NDVI and EVI values: evidence from a field experiment in an alpine meadow

(i) the yellow flower of H. tricuspis significantly increased the red band canopy reflectance, but without apparent variations in near-infrared or blue band reflectance; (ii) the increase in red band reflectance significantly reduced the NDVI and EVI values; and (iii) the EVI was more sensitive than the NDVI to changes in the flower cover. Furthermore, clear decreases were observed in the NDVI and EVI values of the Moderate Resolution Imaging Spectroradiometer (MODIS) product for the study site caused by flower effects. These results suggest that there is a need to examine the effects of flower cover on the NDVI and EVI when they are used for types of vegetation that have profuse seasonal blooms.