## 3 Results
### Jerc-Rd  
For the JERC-RD site, both models showed stronger fidelity to data than for the HF-EMS site. Again, PPA-SiBGC showed higher \(R^{2}\) values and lower RMSE and MAE values compared to LANDIS-II NECN across the range of metrics tested. Yet, the margin between models was smaller for the JERC RD site. While PPA-SiBGC demonstrated higher correlations and lower errors for most metrics tested, LANDIS-II NECN outperformed PPA-SiBGC in a few cases. This includes a higher correlation for NEE, ANPP, and lower magnitude of error for aboveground N, belowground biomass, soil respiration, and SOC. PPA-SiBGC, however, showed correlations equal or higher for all metrics tested, and lower errors for all other metrics. Overall results for the JERC-RD site model intercomparison are shown in Table 8.  
Figure 7: HF-EMS: Simulated and observed species aboveground biomass and relative abundance; (**a**) = biomass; (**b**) = abundance; left = observations, middle = PPA-SiBGC, right = LANDIS-II NECN; note that different scales are used for biomass.  
Time-series carbon exchange metrics for the JERC-RD site, presented in Figure 8, show that modeled NEE values are positively correlated with each other rather than with observed NEE, while the magnitude of error varies from favoring PPA-SiBGC to LANDIS-II NECN. Overall, the PPA-SiBGC model shows a lower magnitude of error for NEE, ANPP, and C\({}_{\text{AG}}\), and slightly higher for r\({}_{\text{soil}}\). Again, for r\({}_{\text{soil}}\) the two models show strong agreement, but underestimate observations by an order of magnitude. For C\({}_{\text{AG}}\) and ANPP, PPA-SiBGC shows good overall fit.  
While both models showed higher performance at the JERC-RD site in comparison to the HF-EMS site, an analysis of simulated species biomass and abundance again indicates greater fidelity of the PPA-SiBGC model to data, as shown in Figure 9. While LANDIS-II NECN greatly overpredicts the rate of longleaf pine growth, PPA-SiBGC matches observed species abundance and biomass trajectories for all species present. While the correlations are high, PPA-SiBGC overpredicts the magnitude of species biomass.  
Our results for the HF-EMS and JERC-RD site model intercomparison exercise show strong performance for both models at both sites. Results for the JERC-RD site are particularly close between the two models. Next, we assess results related to the logistics of model deployment to new computers, users, and modeling sites.  
\begin{table}
\begin{tabular}{l c c c c c c c c} \hline \hline  & \multicolumn{6}{c}{**PPA-SiBGC**} & \multicolumn{6}{c}{**LANDIS-II NECN**} \\ \cline{2-9}
**Metric** & \(\mathbf{R^{2}}\) & **RMSE** & **MAE** & **ME** & \(\mathbf{R^{2}}\) & **RMSE** & **MAE** & **ME** \\ \hline NEE & 0.05 & 0.12 & 0.11 & 0.05 & 0.09 & 0.13 & 0.11 & \(-\)0.05 \\ \(B_{AG}\) & 0.96 & 1.48 & 1.47 & 1.47 & 0.96 & 9.77 & 9.76 & \(-\)9.76 \\ \(C_{AG}\) & 0.96 & 1.63 & 1.63 & \(-\)1.63 & 0.96 & 4.88 & 4.88 & \(-\)4.88 \\ \(N_{AG}\) & 0.99 & 0.29 & 0.29 & 0.29 & 0.96 & 0.05 & 0.05 & \(-\)0.05 \\ \(B_{BG}\) & 0.96 & 10.84 & 10.83 & 10.83 & 0.96 & 1.37 & 1.20 & 1.20 \\ \(C_{BG}\) & 0.96 & 0.25 & 0.25 & 0.25 & 0.96 & 0.96 & 0.95 & \(-\)0.95 \\ \(N_{BG}\) & 0.99 & 1.44 & 1.44 & \(-\)1.44 & 0.96 & 1.60 & 1.60 & \(-\)1.60 \\ \(r_{soil}\) & 0.19 & 0.98 & 0.97 & \(-\)0.97 & 0.05 & 0.90 & 0.90 & \(-\)0.90 \\ ANPP & 0.00 & 0.12 & 0.10 & \(-\)0.10 & 0.03 & 0.62 & 0.60 & 0.49 \\ \(C_{SO}\) &... & 4.30 & 4.30 & 4.30 &... & 0.17 & 0.17 & \(-\)0.17 \\ \(N_{SO}\) &... & 0.38 & 0.38 & 0.38 &... & 0.12 & 0.12 & 0.12 \\ \(B_{Sp}\) & 1.00 & 6.47 & 3.90 & 3.90 & 0.98 & 28.97 & 20.52 & 20.52 \\ \(n_{Sp}\) & 1.00 & 0.02 & 0.01 & 0 & 1.00 & 0.09 & 0.09 & \(-\)0.02 \\ \hline Mean & 0.73 & 2.18 & 1.98 & 1.33 & 0.72 & 3.82 & 3.15 & 0.30 \\ \hline \hline \end{tabular}
\end{table}
Table 8: Model fitness for JERC-RD.