The effects of sulphur dioxide on the spectral curves and chlorophyll concentration of rice canopy

Abstract

This experiment investigated the relationship among the reflectance spectral vegetation indices, sulphur dioxide (SO₂) concentration and chlorophyll concentration (Ch) of rice canopy under different levels of atmospheric SO₂. A split plot field experiment comprising seedlings of three genotypes of rice was exposed to SO₂ at different concentrations. Visible and near infrared canopy reflectance were measured for each SO₂ treatment 30 days and 46 days after transplanting, respectively. SO₂ concentration had a strong negative relationship with Ch-a (chlorophyll-a concentration), Ch-b (chlorophyll-b concentration) and Ch-t (total chlorophyll concentration) (correlation coefficients R from −0.454 to −0.618) at the 0.01 confidence level. Green and red reflectance varied with SO₂ concentrations. Average reflectance were used to calculate difference vegetation index (DVI), normal difference vegetation index (NDVI) and ratio vegetation index (RVI). MERIS Terrestrial Chlorophyll Index (MTCI) was used in this investigation also. One-sample tests showed that for this spectral laboratory there was significant difference at the 0.01 level at those vegetation index (DVI, RVI, NDVI and MTCI). DVI (ρ_red–ρ_green, ρ_nir–ρ_red and ρ_nir–ρ_green), NDVI (ρ_nir–ρ_red/ρ_nir+ρ_red), RVI (ρ_nir/ρ_red) and MTCI were significantly correlated with Ch-b, and Ch-t at the 0.05 confidence level or above. Although MTCI was significantly correlated with Ch-b and Ch-t, it was not strongly correlated with SO₂ concentration. DVI, NDVI (ρ_nir–ρ_red/ρ_nir+ρ_red) and RVI (ρ_nir/ρ_red) were proved effective methods to estimate the injury of rice by SO₂ air pollutant.

Acknowledgements

This project was supported by the National Natural Science Foundation of China (40601062) and Hi-Tech. Research and Development Program of China (863 Program) (2007AA10Z205).