Fig. 4

Relative importance of the growing season length (GSL) and summer peak to the interannual variation in gross primary production (GPP) or integral vegetation index (VI). NDVIB: broadband normalized difference vegetation index, EVIB: broadband enhanced vegetation index, NIRvB: broadband near-infrared albedo of vegetation, NDVIM: MODIS normalized difference vegetation index, EVIM: MODIS enhanced vegetation index, NIRvM: MODIS near-infrared reflectance of vegetation