Figure 1. Changes in the pattern of different spectral reflectance indices with the advancement of growth stages: (a) and (b) represent Exp-1 in year 2003/2004 at Stillwater, and (c) and (d) represent Exp-2 in 2004/2005 at Lake Carl Blackwell. GNDVI, green normalized difference vegetation index; NWI-1, normalized water index 1; NWI-2, normalized water index 2; NWI-3, normalized water index 3; NWI-4, normalized water index 4; RNDVI, red normalized difference vegetation index; WI, water index. The bars indicate standard errors.