## 3 Results
### Changes in Ecotone Extent Inferred from CHM Change and VI Trend  
Figure 7 shows the P90 CHM change (\(\Delta\)P90 CHM), EVI and NDVI trends (indicated by the Theil-Sen slope (\(p<\) 0.05). The analysis of significant VI trends indicated similar greening patterns to the \(\Delta\)P90 CHM expansion of woody ecotones, though the extents were variable. As illustrated in this figure across all four survey areas, the significant slopes for EVI display similar patterns to the observed height-based ecotonal expansions. Conversely, while NDVI also displays similar greening trends, the index overestimates the extent of greening relative to observed ecotonal expansions (Figure 7). Figure 5: Regression results (including 95% CI and coefficient of determination) for CHM30 with NDVI and EVI for 2016/18 over the main landcover classes. Figure 6: Bi-temporal \(\Delta\)CHM30. Changes of less than +/\(-\)1 m (gray) are referred to as “no change” to mitigate influences of data noise and vegetation phenology. White regions represent areas of CHM \(<\)1 m or nondominant landcover classes, which are primarily regions of open water or short seasonal vegetation. (**A–D**) label each of the lidar surveyed areas. Stratifying \(\Delta\)P90 CHM by dominant landcover classes [68] (Figure 1) revealed that -70% of ecotonal expansion (8.5 km\({}^{2}\)), equivalent to -7% of the total survey area, occurred in shrub swamps (Figure 8). Meanwhile, treed swamps accounted for -1.5% of the total expansion in the area. EVI exhibited negative slopes or browning predominantly in upland forest and shrub swamp (zoomed in example in Figure 9B), where no trend was present in the NDVI. This observed browning in the EVI trend, which encompasses a larger area (Figure 8), occasionally corresponds to the contraction of CHM in survey polygon B (Figure 7B), though the extent of the CHM-derived contraction is reduced. Most CHM expansion (Figure 8) occurred along the edge of shrub swamps (zoomed in examples in Figure 9A,C,D). In some cases, shrubs also extended into the marsh land class from adjacent  
Figure 7: CHM-derived ecotonal change compared with significant (\(p<0.05\)) Theil–Sen trend slopes for EVI and NDVI, calculated from Landsat observations between 2000 and 2016/18. Water (in blue) is from the DUC landcover class [68]. **(A–D)** label each of the lidar surveyed areas. swamps (Figure 9A,D). Moreover, comparing the observed ecotonal expansions with the most accurate landcover map provided by [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON] [104] confirms that the expansions observed in our study predominantly occur over the dry shrub class identified in their study, which encompasses three of our four polygons (A, B and C). Figure 8: Comparison of \(\Delta\)P90 CHM, EVI and NDVI Theil-Sen significant slope trends (\(p<0.05\)) by landcover class (VIs slopes are unitless). Figure 9 shows zoomed-in examples of similarities and differences between products alongside the DUC landcover classes. In Figure 9A, although \(\Delta\)P90 CHM expansions were observed on the edges of treed swamp into shrub swamp and marsh, neither EVI nor NDVI reflected those exact expansions. Both NDVI and EVI positive slopes were observed over the inner parts of lowlands. However, when considering only larger positive EVI slope, more similarities with expansions in \(\Delta\)P90 CHM can be seen. NDVI here also showed small positive slopes over uplands. Some of the narrow contractions were reflected in EVI trends as small negatives. In Figure 9B, larger positive slopes of EVI were coordinated with the expansions in \(\Delta\)P90 CHM, over the treed swamp and shrub swamp on the levees. The larger positive NDVI slopes also showed the same pattern; however, the smaller  
Figure 9: Zoomed-in examples comparing \(\Delta\)P90 CHM and significant VI trends (\(p<0.05\)) alongside the DUC landcover classes [68] for reference. (**A–D**) label each of the lidar surveyed areas. positive NDVI slopes were seen over upland forest.