Abstract
AbstractThe present study compared the abilities of the spectral vegetation indices (VI) of Advanced Very High Resolution Radiometer (AVHRR) and Moderate Resolution Imaging Spectroradiometer (MODIS) sensors in accurately detecting seasonal vegetation changes (phenology) with regard to forage quantity and quality. The normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI) were computed with a 10‐day maximum value composite from April 1 to October 31, 2002. The study sites included four meadow steppes and six typical steppes in the Xilingol steppe area of central Inner Mongolia, China. Comparisons of the MODIS‐NDVI and AVHRR‐NDVI profiles revealed that the MODIS‐NDVI temporal profile had a higher fidelity. The dynamic range of the MODIS‐NDVI was then analyzed and its sensitivity in discriminating between vegetation differences was evaluated in sparsely and densely vegetated areas. Estimations of the live, dead standing, total biomass and crude protein (CP) concentration and standing CP were obtained using AVHRR‐NDVI (1.1 km pixels), MODIS‐NDVI and ‐EVI (500 m pixels). Regression analysis revealed that the MODIS‐VI showed a good coefficient of determination (R2 = 0.77–0.83) with regard to estimations of the total and live biomass. Furthermore, the MODIS‐EVI was a good predictor of standing CP (R2 = 0.74) compared with AVHRR (R2 = 0.53). These results suggest that the MODIS‐VI can reliably detect the phenology and forage quantity and quality of grassland steppe areas.
Published Version
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