## 4 Discussion
The maximum estimated mean tree height in and around the Lowveld savanna was about \(\sim\)12 m and in the iSimangaliso St-Lucia site was about \(\sim\)17 m. To assess the performance of the modeling results, we compared the MISR estimates with the 2013-2014 South African National Land-Cover (LC) map [84], and the 2011-2014 Sub-Saharan African tree height product (named H\({}_{Hansen}\), as per its producer [8]). The LC map and the H\({}_{Hansen}\) were produced at 30 m spatial resolution, and thus both were resampled to 275 m resolution using the nearest neighbor interpolator. The LC map was reclassified into proxies of vegetation height where bare ground and grassland were assigned a low tree height, shrubland and woodland were assigned a medium tree height and forest plantations and indigenous forests were assigned a high tree height. Water bodies, mines, and settlements were masked and considered as non forest classes. The H\({}_{Hansen}\) map only consider trees above 5 m only, and thus is generally appropriate to identify the dominant dense woody formation of medium (5-10 m) to tall (>10 m) height. The MISR H\({}_{\text{mean}}\) product generally illustrates the expected tree height gradient patterns of the study sites well. The gradient start from the widely dispersed short trees of the savanna Lowveld area (Figure 9a) to the medium to tall dense trees in indigenous coastal forests and commercial forest plantation areas (Figure 10a) in the iSimangaliso Saint-Lucia area. In the Lowveld savanna area (Figure 9a), the red box denotes the area of interest (AOI) which is enlarged in Figure 9b-d for discussion. Towards the eastern side within the AOI (Figure 9b), a general agreement of low height 1-5 m was observed. This resembles areas with very sparse and low height woody plants due to land use pressure from the surrounding villages (in and around the Kildare and Justicia areas) [58; 110]. On the other hand, tree height is usually 3-6 m in these savanna areas [111], which is also observed in the histogram (Figure 4a). However, outside the AOI on the eastern side of the transect (Figure 9a), it is noteworthy that discrepancies exist across the predominantly basalt geology. The estimated tree heights are overestimated in these areas under low density cover with fine leaf and low height vegetation (the sparse vegetation to no woody). The estimated tree heights are overestimated in these areas under low density cover with fine leaf and low height vegetation (the sparse vegetation to no woody vegetation (dominated mostly by grassland) [112]. In the south of Xanthia in the Bosbokrand Nature Reserve (Figure 9b), higher trees (>6 m) were estimated which could be resulting from various biotic factors (i.e., absence of mega-herbivore and fuelwood extraction) in correspondence to protected areas. This was also in agreement with H\({}_{Hansen}\) map, with tree height >5 m observed under the high density cover. In the iSimangaliso Saint Lucia site, in the dense vegetation areas south east of the AOI (Figure 10b-d--in and around Dukuduku and along coastal forest), we observed a generally good concistency between estimated mean tree height (7-17 m), LC map (medium-high) and H\({}_{Hansen}\) map (>12 m). In the case of the plantations, towards the western area in the AOI (Figure 10b, Mtubatuba area) a general agreement in the estimated mean tree height (higher than 8 m) was observed. This was) well captured by H\({}_{Hansen}\) map (dominated by tree height >5 m). The general MISR H\({}_{\text{mean}}\) underestimation is visible in Figure 6b, in known areas of closed canopy and tall trees. This MISR H\({}_{\text{mean}}\) underestimation could possibly be due to saturation which seems to occur at heights above 15 m (Figure 4b) [113; 114; 115]. The saturation of signal is a known phenomenon in optical sensors, resulting from poor interaction between spectral data and higher volumes with closed canopy of optical sensors.