## Materials and Methods
### PROSAIL RTM and Data Simulation
The total FPAR, direct FPAR and diffuse FPAR were calculated using the following Equations (2)-(6):  
\[\alpha_{\text{s}}^{*}=\ \alpha_{\text{s}}+\frac{\tau_{\text{ss}}\tau_{\text{sd}}+ \tau_{\text{sd}}\tau_{\text{dd}}}{1-\tau_{\text{dd}}\rho_{\text{dd}}^{0}}\alpha _{\text{d}} \tag{2}\]  
\[\alpha_{\text{d}}^{*}=\ \alpha_{\text{d}}+\frac{\tau_{\text{dd}}\tau_{\text{dd}}}{ 1-\tau_{\text{dd}}\rho_{\text{dd}}^{0}}\alpha_{\text{d}} \tag{3}\]  
\[\alpha_{\text{s}} =1-\rho_{\text{sd}}-\tau_{\text{sd}}-\tau_{\text{ss}} \tag{4}\]  
\[\alpha_{\text{d}} =1\ -\rho_{\text{dd}}-\tau_{\text{dd}} \tag{5}\]  
\[\text{FPAR}=\frac{\sum_{\lambda=400}^{\lambda=700}(\alpha_{\text{s}}^{*}\text {E}_{\text{dir}}^{*}+\alpha_{\text{d}}^{*}\text{E}_{\text{dir}}^{*})}{\sum_{ \lambda=400}^{\lambda=700}(\text{E}_{\text{dir}}^{*}+\text{E}_{\text{dir}}^{*} )}=\text{FPAR}_{\text{dir}}+\text{FPAR}_{\text{dir}} \tag{6}\] \begin{table}
\begin{tabular}{l l l l l l} \hline \hline \multirow{2}{*}{**Model**} & \multirow{2}{*}{**Parameters**} & \multicolumn{2}{l}{**Typical**} & \multicolumn{2}{l}{**General Dataset 1**} & \multicolumn{2}{l}{**Specific Dataset 2**} & \multirow{2}{*}{**Step**} \\  & & **Values** & & **Range** & & \\ \hline \multirow{6}{*}{PROSPECT} & C\({}_{\text{ab}}\) (\(\mu\)g cm\({}^{-2}\)) & 40 & 10–80 & 30–60 & 0.5 \\  & C\({}_{\text{ar}}\) (\(\mu\)g cm\({}^{-2}\)) & 8 & 5–20 & 5–20 & 10 \\  & C\({}_{\text{brown}}\) (\(\mu\)g cm\({}^{-2}\)) & 0.0 & 0–0.5 & 0–0.5 & 0.05 \\  & C\({}_{\text{w}}\) (cm) & 0.01 & 0.005–0.05 & 0.005–0.05 & 0.005 \\  & C\({}_{\text{m}}\) (g cm\({}^{-2}\)) & 0.009 & 0.001–0.015 & 0.001–0.015 & 0.001 \\  & N & 1.5 & 1–3 & 1–3 & 0.1 \\ \hline \multirow{6}{*}{SAIL} & LAI (m\({}^{2}\) m\({}^{-2}\)) & 1 & 0.25–7.5 & 1–5 & 0.5 \\  & ALA (\({}^{\circ}\)) & 30 & 10–80 & 30–60 & 10 \\  & hspot (m m\({}^{-1}\)) & 0.01 & 0–1 & 0–1 & 0.2 \\  & SZA (\({}^{\circ}\)) & 30 & 0–90 & 10–60 & 10 \\  & OZA (\({}^{\circ}\)) & 10 & 0–90 & 0–90 & 10 \\  & psi (\({}^{\circ}\)) & 0 & 0–90 & 0–90 & 10 \\  & posoil & 0 & 0–1 & 0–1 & 0.25 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: PROSAIL parameters range and specific meaning. where \(\alpha_{\rm s}^{*}\) and \(\alpha_{\rm d}^{*}\) are the canopy absorptance for direct solar incident flux and hemispherical diffuse incident flux, respectively; \(\alpha_{\rm s}\) and \(\alpha_{\rm d}\) are the isolated canopy layer absorptance for direct solar incident flux and hemispherical diffuse incident flux respectively; \(\tau_{\rm ss}\) and \(\tau_{\rm sd}\) are the direct and bi-hemispherical transmittance for solar flux respectively; \(\tau_{\rm dd}\) is the bi-hemispherical transmittance; \(\tau_{\rm sd}\) is the directional-hemispherical reflectance factor for solar incident flux and \(\tau_{\rm dd}\) is the bi-hemispherical reflectance factor; \(\rho_{\rm sd}\) and \(\rho_{\rm dd}\) are the directional-hemispherical reflectance for solar flux and bi-hemispherical reflectance above the canopy, respectively; \(\rho_{\rm dd}^{\rm b}\) is the bi-hemispherical reflectance at the bottom of the canopy; and \(\rm E_{\rm dir}^{\rm t}\) and \(\rm E_{\rm dif}^{\rm t}\) are the direct PAR and diffuse PAR, respectively.