## 3 Results
### Analysis of VIs and SIF at Vegetation Group Level (for Peatland, Grassland, and Forest Ecosystems)  
We explored vegetation information representing different plant traits (i.e., VIs and SIF) (Figure 7) considering peatland, grassland, and forest ecosystems. The dynamics of signals within particular vegetation groups were assessed to gain insight into biophysical, biochemical, and structural differences across vegetation types representing different ecosystems. The highest values of greenness-sensitive indices (i.e., SR, NDVI) were obtained for low birch bush (LBB) and alder forest (AF) due to their green leaves and dense canopies during the time of SWAMP campaign. Calcareous fens (CF) and transition mires (TM) showed the lowest values for greenness indices across peatland groups of vegetation since, due to the dominance of _Sphagnum_ spp., their surface became whitish at the time of the campaign. Within the grassland group, the highest values of greenness indices were obtained for meadows and mesic pastures (MMP). Mowed meadows and mesic pastures (CM), in contrast, showed low values for greenness indices, possibly due to the low vegetation coverage in that area during the campaign time. Young deciduous forest (DF) and secondary forest communities with _Alnus glutinosa_ (SFAG) were characterized by the highest greenness index values, whereas herbaceous vegetation of forest clearings (HV) showed the lowest values among the forest group.  
A contrasting picture is obvious for the PRI: The highest PRI values were found for TM and CF, whereas PRI was lowest for AF within the peatland group. CM and HV showed the highest PRI signals, whereas MMP, SFAG, and young DF showed the lowest PRI signals within the grassland and forest groups, respectively.  
Figure 7: Bar diagram presenting the average values of the observed VIs and SIF derived from HyPlant data; (**a**) SR, (**b**) NDVI, (**c**) EVI, (**d**) PRI, (**e**) SIF\({}_{760}\), and (**f**) SIF\({}_{687}\). The names of the individual vegetation groups are written at the bottom of the bars and correspond to the abbreviations provided for Figure 3a. The dark grey group of bars represents the peatland ecosystem; light grey bars represent different kinds of grasslands (including the post-agricultural land, pioneer vegetation of sandy and shallow soil); and white grey bars stand for different kinds of forests. Error bars represent standard deviation.  
Simultaneously, the highest to the lowest EVI signals were found for LBB, AF, and rush vegetation (RV), respectively, within the peatland group. Highest to lowest EVI are shown for MMP to CM, respectively, within the grassland group and riparian forests (RF), SFAG to the HV in the forest group, respectively.  
The highest SIF\({}_{687}\) and SIF\({}_{760}\) values were found over LBB and AF within the peatland vegetation group; for MMP within the grassland group; and for SFAG and young DF (which is in agreement with [PERSON] et al. [16]) within the forest group. The lowest SIF signals in both O\({}_{2}\) absorption bands were recorded for CF and TM within the peatland group, for CM within the grassland group, and for HV within the forest group.  
Positive relationships have been found for both SIF\({}_{687}\) and SIF\({}_{760}\) with both greenness indices SR and NDVI (Figure 8). At the same time, a negative relationship was observed between SIF and PRI. Relationships between SIF\({}_{760}\) and SIF\({}_{687}\) with NDVI, SR, and PRI were found to be statistically significant (\(p<0.01\)) at the vegetation group level (Figure 8). However, a weak relationship was found between SIF\({}_{760}\) and EVI, although the correlation between SIF\({}_{687}\) and EVI was significant with \(p=0.012\).