years, and R
2 values are 0.92, 0.93, and 0.94 for 2001, 2003, and 2005, respectively. As shown in Table 5.2, the root mean square deviation (RMSD) values of
maize are less than 3 g C m
-2 d
-1 (2.4, 2.7, and 2.0 g C m
-2 d
-1 for 2001, 2003,
and 2005, respectively). The seasonal sums of GPP over the crop-growth period
between GPP VPM and GPP EC are also compared in Table 5.2. The relative error
(%RE) ranged from 14.8 to 5.0 %.
Figure 5.5 shows the scatterplots between GPP VPM and GPP EC of soybeans
over the crop-growth period across individual years and all years. The correlation
between GPP VPM and GPP EC for soybeans is less strong than the relationship for
maize. However, the R
2 is still relatively high, with the value of 0.85 across
multiple years, and R
2 values are 0.82 and 0.88 for 2002 and 2004, respectively.
Fig. 5.4 Scatterplots between GPP EC and GPP VPM of maize in individual and multiple years
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