8.4.3 Total Biomass Data and Their Usefulness for Model
Evaluations
Total biomass data for 24 sites have been calculated based on field-collected above
ground biomass in 2005 (Fig. 8.5). Total biomass averaged 95.6 g/m
2 , with a range
from 43 to 172 g/m
2 .
To test the usefulness of the biomass data for model evaluation, each sampling
site was examined to see how well it can represent its surrounding area using the
SPOT 5 image. Figure 8.6 shows that only three sampling sites (SG2C, SG9C, and
U4T3) have a consistent NDVI between 100 Â 100 m
2 site and its surrounding
areas, while the rest (21 sampled sites) shows a moderate to large difference.
Dramatic differences between 100 Â 100 m
2 NDVI and 250 Â 250 m
2 NDVI can
5
0
20
40
60
80
100
120
140
160
10 15 17 19 21 23 24 25
Average NPP
Maximum NPP in the VG2D site
Minimum NPP in the VG13D site
C:N values used to drive the model
Simulated NPP (g C m -2
yr -1
)
27 29 31 33 35 45
VG13D site − Minimum Simulated NPP
VG2D site − Maximum Simulated NPP
Fig. 8.4 The sensitivity of spatial BIOME-BGC model to foliar C:N ratio. The SPOT 5 NDVI
scene showing VG13D site in the bottom left and VG2D site in the bottom right (The tone from
black to white indicating NDVI values from low to high)
8 Grassland Productivity Simulation: Integrating Remote Sensing. . .
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