## 2 Results and Discussion
### Relationship between FPAR and Vegetation Indices  
Figure 5 demonstrates the variations of canopy FPAR (including FPARPAV, FPARNFV and the total FPAR) with four vegetation indices for broadleaf deciduous forests. The total  
Figure 4: Vegetation indices of evergreen coniferous forests.  
Figure 3: Vegetation indices of broadleaf deciduous forests.  
FPAR, FPAR\({}_{\text{PAV}}\) and FPAR\({}_{\text{NPV}}\) had different change patterns with vegetation indices. The total FPAR and FPAR\({}_{\text{PAV}}\) increased with vegetation indices regardless of the proportion of leaf area. For FPAR\({}_{\text{NPV}}\), its variations with vegetation indices were more complex than the total FPAR and FPAR\({}_{\text{PAV}}\). With the increase of vegetation indices, FPAR\({}_{\text{NPV}}\) increased initially (PAI < 0.2) and thereafter decreased (PAI > 0.2). Furthermore, the trajectory of FPAR-vegetation index varied with the proportion of leaf area in 2-D space composed of FPAR and vegetation index. For a given value of anyone of vegetation indices, FPAR\({}_{\text{PAV}}\) values increased with the proportion of leaf area in canopies, while the total FPAR and FPAR\({}_{\text{NPV}}\) decreased. Pearson correlation coefficients between the total FPAR, FPAR\({}_{\text{PAV}}\) and each vegetation index were calculated, and they were high and can pass the test at the 0.01 significance level according to Pearson correlation critical values table. This indicated there were significant linear positive correlations between them. However, correlation coefficients between FPAR\({}_{\text{NPV}}\) and four vegetation indices were low (r < 0.12). Particularly, the correlation coefficient between FPAR\({}_{\text{NPV}}\) and EVI2 was only 0.019. NDVI had closer relationship with the total FAPR than other three vegetation indices. EVI demonstrated better consistence with FPAR\({}_{\text{PAV}}\). When the proportions of leaf area rose, the correlation coefficients between FPAR and four vegetation indices increased. For example, the correlation coefficient between FPAR\({}_{\text{PAV}}\) and NDVI, EVI, EVI2, SAVI decreased by 0.03, 0.015, 0.017, 0.022 when the proportions of leaf area in canopies varied from 0.5 to 0.98.  
For evergreen coniferous forests, the relationships between the canopy FPAR (including FPAR\({}_{\text{PAV}}\), FPAR\({}_{\text{NPV}}\) and total FPAR) and four vegetation indices were similar with those of broadleaf deciduous forests (Figure 6). The significant linear relationship can be found between canopy FPAR (including the total FPAR, FPAR\({}_{\text{PAV}}\)) and each vegetation index, while the relationship between FPAR\({}_{\text{NPV}}\) and each vegetation index was nonlinear. For evergreen coniferous, the total FPAR and FPAR\({}_{\text{PAV}}\) had the closest relation with NDVI (r = 0.993), EVI (r = 0.99), respectively, but correlation coefficients FPAR\({}_{\text{NPV}}\) between and  
Figure 5: The relationship between FPAR and vegetation indices for broadleaf deciduous forests.  
four vegetation indices were less than 0.07. With the increase of the proportion of leaf are in canopies, correlation coefficients between FPAR\({}_{\text{PAV}}\) and four vegetation indices increased.