The study of riparian vegetation is based on the observation of natural plant communities spontaneously colonizing newly exposed areas following the erasure of the Vezins and La-Roche-Qui-Boit dams.

The vegetation monitoring system includes two complementary approaches:

i) a vegetation sampling method based on floristic surveys (composition & structure) carried out within a series of quadrats positioned along a transect

ii) a monitoring of the vegetation units (UV) observed within the valley

This dataset specifically concerns the overall characterization observed on each quadrat in terms of strata and concerns only the Sélune Observatory (2021-2026).

The sampling monitoring system is based on measurements distributed at different points in space (longitudinally and laterally). It aims to identify the diversity of flora and vegetation and describe the structure of emerging formations and plant communities within the neo-valley. Implemented annually (sub-annual only for 2021, before dismantling), this monitoring aims to identify and characterize the evolution trajectories of these vegetation over time.

The vegetation sampling protocol is implemented at several stations located along the course of the Sélune and at the mouth of several tributaries located in the right-of-way of the two former reservoirs. The sample of stations is supplemented by a batch of stations positioned outside the right-of-way of the two former reservoirs, downstream and upstream, which constitute so-called "reference" stations.

For each station, a transect is established perpendicular to the channel, from the bank to a reference point located at the level of the former water reservoir (i.e. 60m NGF for Vezins & 28.5m NGF for LRQB). Along this transect, 25m2 (5mx5m) quadrats are positioned according to previously set distance intervals. These quadrats (named Q1 to Q1+n) constitute the elementary unit within which abiotic (slope, texture...) and biotic (composition, structure) parameters are characterized and evaluated. The number of quadrats sampled per station varies depending on the width of the exposed bank (or transect length). It is completed by a reference quadrat, located beyond this maximum value (named Q0).

The inventory of vascular flora, i.e. herbaceous and woody plant species within the quadrats, aims to be exhaustive and to identify them up to the specific or even sub-specific rank.

The overall characterization mentioned mainly concerns, for each quadrat, the type of soil encountered (see attribute dictionary), the slope (see attribute dictionary), the proportions of water cover, bare soil, and litter, as well as, for each of the 6 defined strata (see attribute dictionary): the considered height limits, the maximum and average height, and the proportion of overlap (relative to the 25m2 of the quadrat).

This layer gives, for each monitoring quadrat of vegetation sampling from 2021 to 2026, the following information:

– Quadrat information (id, code, number and distance from its centroid to the station reference point),

– Campaign information (id, code, date, campaign),

– Station information (code, name, protocol applied, number of quadrats, code for the associated Sélune reference point and, as a result, positioning on the catchment area, distance to sea, distance to source and watercourse, watercourse reference altitude)

– Information on the transect by campaign (number and length, X, Y, LON, LAT coordinates of the reference points “NGF” and end point “bank”)

– Information concerning the strata (identified or not), soil typology, water, bare and litter coverings, as well as details for each stratum (name of stratum ‘muscinal’, “herbaceous”, “young plant shrub,” “low shrub', “high shrub” and “arborescent, the height limits of the stratum, the associated overlap, the maximum and average heights of the stratum)

– “Point” geometry (default) corresponding to the transect reference point