*2.1. Study Site*

The study site is the Bernadouze peatbog (Latitude: 42◦47 N, Longitude: 1◦24 E; approximatively 2 ha), which is part of Human-Nature Observatory "Haut-Vicdessos" located in Ariège (Pyrénées, France) (Figure 1) and supported by the French CNRS and the LabEx DRIIHM. It is a long term monitored study site where hydrological, climatological, botanical, archeological, remotely sensed surveys are regularly conducted.

**Figure 1.** Location of the in situ spectroradiometer measurements—True color composite made from hyperspectral (HySpex) aerial imageries acquired on the 09/12/2014 (R = 639.98 nm,G= 549.06 nm, B = 461.79 nm).

#### *2.2. Field Data Collection*

In this study, thirteen vegetation units with ecological values and potentials (i.e., biodiversity) have been identified in the Bernadouze peatbog. These units are named hereafter "vegetation types" according to the dominant land cover type or to the potential development of interesting plant species which may have ecological values (Table 1). For each type, several locations have been surveyed to characterize their plant species composition (Table A1).

For all these 32 sample locations (Figure 1), radiances are measured at three different dates over 9 days in September 2014 (4 September 2014, 5 September 2014, 12 September 2014) under sunny and cloudless conditions between 10:00 a.m. and 1:00 p.m. and Sun's azimuth angle ranging from 106◦ and 160◦. Data have been collected using an Analytical Spectral Device (ASD) spectroradiometer which ranges on the reflective domain (350–2500 nm) with a 3–12 nm spectral resolution depending on the spectral domain. Its spectral specifications are summarized in Table 2.

**Table 1.** Species names, number of measurements, number of locations and total number of spectra collected.


**Table 2.** Analytical Spectral Device (ASD) FieldSpec Pro specifications.


To measure the reflectance of a sample plot (*ρ*) the reflectance of a white reference (*ρ*ref) is required. This latter was obtained with a Spectralon (Labsphere, North Sutton, NH, USA) panel. Finally, after dark current correction, *ρ* is given by:

$$
\rho = \frac{L\_{\text{sum}}}{L\_{\text{ref}}} \rho\_{\text{ref}} \tag{1}
$$

where *L*sam is the measured radiance from the sample plot and *L*ref is the measured radiance from the white reference.

The sensor was positioned approximatively 1 m over the target with a 10◦ field of view. Consequently the ground spatial resolution is 0.18 m. The ASD was configured to collect 20 samples and automatically average in order to provide a single mean spectral measurement. Then a total of 7 to 53 field spectroradiometer measurements, i.e., spectral signatures, depending on vegetation type was taken.
