## 4 Results  
### Stand Tree Density and Woody Biomass in Haifa's Wildland-Urban Interface Area  
All three vegetation indices showed positive moderate relationships with field-based stand density measurements (Table 4). R\({}^{2}\) of the VIs-stand density correlations ranged between 0.26 and 0.62, where the highest correlation found was with the GCC for both satellites and with the image corresponding to 23 August 2016 for Planet and 12 November 2016 for Sentinel-2A. The R\({}^{2}\) of the VIs-DBH correlations were lower, i.e., within the range of 0.22 and 0.48, with GCC being the best VI for Planet and GNDVI and GCC for Sentinel-2A (Table 4).  
Figure 4 shows a scatterplot of GCC vs field measurements of stand density and DBH for Planet (image acquired in 23 August 2016). The GCC calibrated stand density linear regression equation was successfully validated with the stand count conducted in an area nearby the WUI, with R\({}^{2}\) = 0.56 (Figure 4c).  
We then used the GCC calibrated stand density and DBH equations to derive the satellite-based stand density and DBH maps.  
Figure 5 shows the stand density and AGB maps from Planet and Sentinel 2-A for UR and WLD domains. Planet-derived stand density uncertainty maps using the MAE of the linear fit are provided in Figure A3. Stand density and AGB were notably higher at the eastern parts of the WLD domain, near the urban area, and at the grove area within the UR. In general, Planet-derived maps show slightly higher stand densities/AGBs at the grove area within the UR domain.  
The mean stand density and AGB, which were notably higher in the UR than in the WLD, are shown in Table 5.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Planet**} & \multicolumn{3}{c}{**Sentinel-2A**} \\ \hline
**Date** & **NDVI** & **GNDVI** & **GCC** & **NDVI** & **GNDVI** & **GCC** \\ \hline \multicolumn{6}{c}{Tree density} \\
22 November 2016 & 0.45 & 0.26 & 0.49 & 0.54 & 0.41 & 0.62 \\
12 November 2016 & 0.27 & 0.27 & 0.45 & 0.55 & 0.42 & **0.64** \\
13 October 2016 & 0.47 & 0.50 & 0.56 & 0.51 & 0.47 & 0.56 \\
23 August 2016 & **0.54** & **0.55** & **0.65** & **0.58** & **0.50** & 0.59 \\ AVG & 0.43 & 0.40 & 0.53 & 0.54 & 0.45 & 0.60 \\ \hline DBH & & & & & & \\
22 November 2016 & 0.23 & 0.24 & 0.30 & 0.29 & 0.22 & 0.29 \\
12 November 2016 & 0.27 & 0.27 & 0.36 & 0.31 & 0.25 & **0.37** \\
13 October 2016 & 0.22 & 0.29 & 0.35 & **0.35** & **0.37** & 0.31 \\
23 August 2016 & **0.37** & **0.39** & **0.48** & 0.31 & 0.27 & 0.32 \\ AVG & 0.28 & 0.30 & 0.37 & 0.31 & 0.28 & 0.33 \\ \hline \hline \end{tabular}
\end{table}
Table 4: R\({}^{2}\) of the correlation between the three VIs (NDVI, GNDVI and GCC; see Table 2) and stand density and DBH measured at the field survey. VIs were correlated with stand density and DBH using four images taken at different dates prior to fire. Best correlations are indicated in bold.  
Figure 4: (a,b) Scatterplots of GCC derived from Planet in 23 August 2016 vs. field-measured stand density and DBH. (c) Estimated vs observed stand density, using the GCC calibrated linear fit (from **a**) and stand count in a nearby area. Note that in (c), some of the 29 plots have the same value.