## 5 Conclusions  
Our results are the first experimental evidence of the possibility of retrieving both red (SIF\({}_{687}\)) and far-red (SIF\({}_{760}\)) chlorophyll fluorescence signals over heterogeneous ecosystems, such as peatlands. The reliability and capacity of a novel airborne HyPlant sensor were also demonstrated in this paper, which successfully captures complex vegetation signals from extremely heterogeneous peatlands. The results are valid for some specific conditions, and the status of the peatland is dependent on the hydrometeorological and climatological conditions related to the summer conditions. Hence, the findings cannot be extrapolated and may not be valid out of the season, when the status of the peatland, the greenness of the surface, and biomass of plants are different. Although all the results of this study depend on one-day airborne measurement, the results have illustrated a promising method to understand the dynamic degree of relationships between SIF and VIs at different hierarchical scales using HyPlant, the airborne demonstrator of ESA FLEX mission. We conclude on the importance of hyperspectral RS information representing a diverse set of vegetation traits--including biochemical, structural, and functional traits--to comprehensively assess the complex ecosystems, such as peatlands, and to capture the wide diversity of different vegetation groups and peatland plant communities. In such a complex ecosystem like peatlands, we suggest quantifying and analyzing red and far-red fluorescence peaks to improve our understanding and facilitate predictions of functional dynamics in larger vegetation groups and small plant community levels, which are determined by complex interplays between functional and structural regulations [89; 90; 91; 92]. Comprehensive measurements of SIF, fAPAR, LAI, and VIs help in the advance estimations of photosynthesis activity, biochemical and structural traits, and facilitate assessments of the wide functional diversity of vegetation groups and plant communities occurring in such ecosystems. Since SIF is considered as a prime indicator of photosynthetic activity and is clearly correlated with fAPAR and LAI, we can assume that diversity in SIF maps reflects the diversity in their photosynthetic activity, which may correspond to photosynthesis biomass of vascular plants. Our results successfully support this claim for the first time in heterogeneous surfaces like peatlands. This may further enrich our knowledge on a local, regional, and global understanding of the photosynthetic activity of natural ecosystems. The following are available online at [[http://www.mdpi.com/2072-4292/11/14/1691/s1](http://www.mdpi.com/2072-4292/11/14/1691/s1)]([http://www.mdpi.com/2072-4292/11/14/1691/s1](http://www.mdpi.com/2072-4292/11/14/1691/s1)), Table S1: Description of 52 plant communities inside the peatland. Conceptualization, S.B., A.R., U.R., and R.J.; Data Curation, S.B., P.R., A.S., S.C., M.G., S.R., and R.J.; Formal Analysis, S.B., P.R., S.C., M.S., and R.J.; Funding Acquisition, U.R., A.M.A., I.R., D.S., and R.J.; Investigation, S.B., A.R., U.R., P.R., A.S., S.C., T.J., A.M.A., A.H., E.T., M.C., A.B., M.S., K.S., M.G., S.R., M.S., M.D.I., I.R., C.V.D.T., A.D., D.S., and R.J.; Methodology, S.B., U.R., P.R., S.C., and R.J.; Project Administration, U.R., A.S., A.M.A., D.S., and R.J.; Resources, U.R., P.R., A.S., S.C., A.M.A., M.J., and R.J.; Software, P.R., S.C., M.S., and R.J.; Supervision, A.R., U.R., S.C., and R.J.; Validation, S.B., A.S., T.J., A.M.A., H., E.T., A.B., C.V.D.T., A.D., and R.J.; Visualizing, S.B., P.R., S.C., M.G., and R.J.; Writing: Original Draft, S.B., A.R., S.C., and R.J.; Writing: Review and Editing, S.B., A.R., U.R., S.C., A.H., E.T., M.C., M.S., C.V.D.T., A.D., K.S., and R.J. The research was co-funded by the COST Action ES1309 OPTIMISE, FP7 European Facility for Airborne Research (EUFAR), FLEX-EU ESA (Contract No.