## Discussion
### Sensitivity Analysis of Peatland Plant Communities  
The results from Figure 9 have demonstrated the dynamics of VIs and SIF signals from heterogeneous peatland plant communities. The outputs were explored by the potential capability of the high-resolution HyPlant images to showcase the extracted VIs and SIF signals from small-scale homogeneous to heterogeneous peatland plant communities. No such studies to date have used the HyPlant hyperspectral imaging spectroscopy system to understand the dynamics of heterogeneous peatland plant community signals of VIs and fluorescence in both red and far-red regions. In a dynamic ecosystem like peatland, the spectral signatures of plants species, which represent the biodiversity of the peatland as well as the biophysical properties of vegetation cover, are very dynamic by nature [8]. Due to the frequent change of the environmental conditions, peatland plant species are continuously facing challenges for their survival, which ultimately impact their biophysical conditions and can be observed by the deviation in spectral reflectance [81]. This variation is not surprising, as the green leaves in the very short term (minutes, hours, days) remain green, but the photosynthesis decreases under stress condition [82]. Such kind of very dynamic situation may impact SIF-VIs relationships, particularly for peatland vegetation. Even the magnitude of the frequently changing rate of photosynthesis due to certain local stress factors--such as extreme temperature, direct sunlight, a temporary shortage of water, or nutrient content--may hamper the SIF-VIs agreement [83]. In the peatland ecosystem, water table depth plays a crucial role in the plants and determines the species composition of the peatland [81]. A slight drop or lift in water table may impact the vegetation functionality drastically and may also influence the SIF and VIs. SPDC and CC in the ME category were perennial grasses with long canopy distribution, which are highly dependent on the soil moisture content [84; 85]. In July 2015, these plant communities were in their full phase of growth, which was reflected by the higher values of greenness indices (SR, NDVI) and EVI. Also, values of SIF\({}_{687}\) were the highest for these communities, although SIF\({}_{760}\) was nearly three times higher for SPDC than for CC plant communities. At the same time, MG was suffering from low vegetation coverage during the campaign time, which explains the low value of greenness indices and both SIFs. Similarly, CL in the PR category and SCR in the FE category were tall and dense vegetation, represented by the highest values of greenness indices and one of the highest values of SIF\({}_{760}\). We observed the plant communities like SPDC in the ME category, CL in the peatland rush vegetation category, and SCR in the FE category all had higher EVI signals due to their high green biomass content. No such variation of PRI signals was observed in the ME category. ST in the FE category was observed with a very high PRI and the lowest SIF signals. A clear gradient was observed in SIF\({}_{760}\) within the plant communities under different vegetation categories. For the vascular plant communities, high biomass could be the reason for higher SIF\({}_{760}\) signal. An increase in the biomass of vascular plants is known to accelerate the rates of photosynthesis [86]. In the homogeneous meadows category, poor AP to rich SPDC was observed with the lowest to highest SIF\({}_{760}\) emissions. For heterogeneous rush vegetation, coverage and dominance of some vascular plant species might be the main reason for the lowest to highest SIF\({}_{760}\) signal emission. Less covered and diverse PC emitted lower SIF\({}_{760}\), while highly dense and more species-rich TP emitted higher SIF\({}_{760}\). In the FE category, an abundance of vascular plant species might be a cause for the lowest to highest SIF\({}_{760}\) emission, too. The lowest SIF\({}_{760}\) signal originated from ST, characterized with very low abundance and biomass of vascular plants.