a To make the performance in the calibration and the
validation comparable, the mean values of two years’ field measurements
for each type of observation were used here for calculatingNRMSE . W above, aboveground biomass;
W grain, grain weight; W leaf,
leaf weight; N above, aboveground N content;
N grain, grain N content; N leaf,
leaf N content in the canopy; and LAI, leaf area index.