## 3 Results
### Performance of VIs and SIF Signals at the Peatland Plant Community Level  
A wide range of VIs and SIF signals was observed for different peatland plant communities (see Figure 9), mainly due to their huge heterogeneity in terms of species richness, composition, dominance, structure of canopies, and functional variability. Due to this heterogeneity, the whole peatland plant community was categorized into three groups: i) Meadows (ME), ii) peatland rush vegetation (PR), and iii) fen vegetation (FE). ME represents the grasslands, whereas PR refers to several flowering peatland plants, and FE refers to the peatland mites. A detailed description of plant communities within the identified plant categories is provided in Table S1 (supplementary material). Among these three categories, ME were considered as spatially homogeneous patches of vegetation, whereas PR and FE vegetation groups reflect the heterogeneous nature of peatlands typically composed of many different species. According to the spatial coverage of our peatland site, PR and FE vegetation groups occupied the largest area of the peatland (90%) in contrast to meadows (10%) located at the edge of the peatland. Figure 9 shows that within different peatland plant categories (ME, PR, and FE), each plant community was very individual and was characterized by unique values of VIs and SIF. The plant communities--like CC and SPDC from the ME category, CL from PR, and SCR from the FE category--showed the highest values of SR and NDVI. Whereas, MG and AP from the ME category, and CM and PC from the PR category,  
Figure 8: Correlation analysis of SIF at 760 nm (Figure 8a–d) and at 687 nm (Figure 8e–h) with selected remotely sensed VIs (SR, NDVI, and PRI) at the vegetation group level. Error bars represent standard deviation. Here, black dots denote peatland, light grey dots denote grasslands, and white represents forest vegetation groups. showed the lowest values of SR and NDVI. Similarly, ST and CLa within the FE category also showed the lowest values of SR and NDVI. The highest EVI was observed for SPDC, CL, and SCR in the ME, PR, and FE categories, respectively. Whereas, MG, TP, and CLa showed the lowest EVI in the ME, PR, and FE categories, respectively. In the ME category, all five plant communities were found to have almost similar PRI values. Whereas, CM and CL were found to have the highest PRI values under the PR category. Within the whole analyzed peatland plant communities, the highest PRI values were found for ST, and the lowest PRI values were observed for TL and TP within the PR community and SCR within the FE community. All the plant communities within each group of vegetation (ME, PR, and FE) were sorted according to \(\text{SIF}_{760}\) for clear visualization of the data in Figure 9. SPDC, TP, and CLa were recorded with the highest \(\text{SIF}_{760}\), whereas AP, PC, and ST were recorded with the lowest \(\text{SIF}_{760}\) in the ME, PR, and FE categories, respectively. The highest and the lowest \(\text{SIF}_{687}\) signals in the ME category were observed for SPDC, CC, and AP, respectively. CM and CD were observed to have the highest \(\text{SIF}_{687}\) values, whereas TL and ST the lowest within PR and FE categories, respectively. To understand relationships between SIF and VIs at the narrower plant community-scale, from homogeneous meadows to heterogeneous rush and peatland vegetation, we assessed the 1:1 linear correlation between selected VIs and SIF within each vegetation category (Figure 10). In the ME category, relationships between SR, NDVI, EVI, and PRI with \(\text{SIF}_{760}\) and \(\text{SIF}_{687}\) were positive with \(\text{R}^{2}\) ranging from 0.57 to 0.92 for SR, from 0.44 to 0.88 for NDVI, from 0.61 to 0.86 for EVI, and from 0.24 to 0.87 for PRI. Besides for PRI-\(\text{SIF}_{687}\), SR-\(\text{SIF}_{760}\), NDVI-\(\text{SIF}_{760}\), and EVI-\(\text{SIF}_{760}\), the rest of the investigated relationships were significant at \(p<0.05\).