# Remote Sensing and Bio-Geochemical Modeling of Forest Carbon Storage in Spain
## 5 Results
### NPP in Future Condition  
Simulated annual forest NPP in possible future scenarios of climate change presents a spatial pattern similar to that exhibited during 2005-2012 (Figure 4a,b). This is shown in Figure 4c, where the average annual forest NPP calculated using Equation (4) with GPP\({}_{\text{BGC}}\), \(\Delta T=+2\)\({}^{\circ}\)C, and \(\delta\)PRE = -20% for the corresponding 8-year period is represented. However, it can be appreciated how the regions that already presented great (or small) NPP in Figure 4a,b present even greater (or smaller) NPP in Figure 4c. The basic statistics of Figure 4c are summarized in Table 6. A comparison of Table 6 with NPP with GPP\({}_{\text{BGC}}\) in Table 5 illustrates that minima are all practically the same; maxima are greater in Table 6 for all forest types; means are greater in Table 6 except for HENF, for which it is smaller; and standard deviations are greater in Table 6 for EBF, LDBF, and LENF, while they are nearly equal for HDBF and HENF. Figure 5 shows the variation of annual forest NPP with air temperature increments (\(\Delta T\)) and precipitation reductions (\(\delta\)PRE) for a single pixel of each forest type. The main eco-climatic features of the selected pixels together with their geographic coordinates are summarized in Table 7. The pixels were selected for the sake of homogeneity and representativeness: at least a \(5\times 5\)-pixel window (\(7\times 7\) for HENF) with the same forest type surrounding each pixel was imposed, and they are also representative of the main eco-climatic features of each forest type (Table 1). In the case of EBF, the surface is nearly flat and only slight decreases in NPP due to increases in air temperature were found. Figure 4: Average annual forest NPP obtained through the modeling strategy presented in Section 2: (**a**) using GPP estimated using Equation (1); (**b**) using GPP simulated using Biome-BGC; (**c**) using GPP simulated using Biome-BGC, \(\Delta T=+2\)\({}^{\circ}\)C, and \(\delta\)PRE = -20%. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Forest Type**} & \multicolumn{5}{c}{**GPP\({}_{\text{PEM}}\)**} & \multicolumn{5}{c}{**GPP\({}_{\text{BGC}}\)**} \\ \cline{2-10}  & **Min** & **Max** & **Mean** & **Std** & **Min** & **Max** & **Mean** & **Std** \\ \hline
**EBF** & 128 & 1778 & 916 & 308 & 13 & 1495 & 828 & 243 \\
**LDBF** & 310 & 1762 & 1229 & 202 & 201 & 1611 & 1156 & 220 \\
**HDBF** & 1 & 1785 & 1049 & 254 & 174 & 1729 & 1003 & 312 \\
**LENF** & 7 & 1876 & 864 & 311 & 0 & 1909 & 784 & 284 \\
**HENF** & 4 & 1592 & 774 & 220 & 205 & 1681 & 773 & 256 \\ \hline \hline \multicolumn{10}{c}{**NPP with GPP\({}_{\text{PEM}}\)**} \\ \cline{2-10}  & **Min** & **Max** & **Mean** & **Std** & **Min** & **Max** & **Mean** & **Std** \\ \hline
**EBF** & 8 & 876 & 181 & 168 & 12 & 470 & 143 & 110 \\
**LDBF** & 36 & 832 & 418 & 138 & 17 & 788 & 385 & 134 \\
**HDBF** & 4 & 661 & 232 & 128 & 14 & 679 & 218 & 134 \\
**LENF** & 1 & 197 & 149 & 116 & 7 & 495 & 123 & 87 \\
**HENF** & 1 & 549 & 125 & 84 & 9 & 583 & 123 & 87 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Minimum (min), maximum (max), mean, and standard deviation (std) of the different average annual GPP products and their corresponding NPPs involved in the estimation of annual NPP per forest type. GPP\({}_{\text{PEM}}\) was estimated using Equation (1). GPP\({}_{\text{BGC}}\) was simulated using Biome-BGC. All values are expressed in g m\({}^{-2}\) a\({}^{-1}\). NPP in LDBF was strongly reduced when both an increment of air temperature of at least 2 \({}^{\circ}\)C and a reduction of precipitation of at least 30% were combined, but a softer reduction in NPP was also observed when precipitation was reduced by 40% independently of the variation in air temperature. NPP in HDBF did not present any significant change due to increments in air temperature nor to reductions in precipitation. NPP in LENF was slightly but consistently decreased as precipitation was reduced.