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SERIPAGE: How are the interactions between agricultural systems, landscape structure and spontaneous plant biodiversity changing from slopes to watercourses?

Coordinator(s)

Claudine Thenail

Scientific context

The operations to remove the dams on the Selune will modify the hydrodynamic and sedimentary conditions and the transport of seeds and propagules (plant strains) in the Selune. These modifications to the watercourse will lead to significant changes in the aquatic, riparian and terrestrial vegetation in interaction with the dynamics of the landscape and agriculture. These potential changes to existing vegetation are particularly important for :

• The conservation of plant biodiversity and the management of invasive species,
• The role of flora as habitats/resources for fauna,
• Combating bank erosion and trapping particles, which helps to improve water quality.

These changes will depend on the way in which the emptying, sediment management and dismantling of the hydroelectric dams are carried out. It is therefore important to define the initial state and monitor changes in the watercourse and vegetation from the start of the works.

Subject(s) of study

The project focuses on aquatic, riparian and terrestrial vegetation and their interactions in landscape and agricultural dynamics.

Objectives

The aim of this project is to develop systems, indicators and knowledge repositories for monitoring changes in spontaneous vegetation, along two lines:

1. Monitoring changes in aquatic, riparian and terrestrial vegetation at the level of the watercourse, and in the renaturation dynamics of currently flooded watercourses and their margins,
2. Monitoring changes in the interactions between riparian zones, the landscape and agricultural systems on slopes.

Methods

For this project, three main areas are considered along the Selune, in connection with the pre-dismantling operations (effect of lowering the reservoirs, emptying):

• The downstream zone, downstream of the reservoirs,
• The lakes zone, including the La-Roche-Qui-Boit and Vezins lakes,
• The upstream zone, upstream of the reservoirs as far as the head of the basin of the main course of the Selune.

Several monitoring and analytical methods are used to monitor vegetation and agricultural dynamics:

• Acquisition of high-resolution drone images,
• Remote sensing mapping along the hydrographic network,
• Definition of indicators by analysing the images acquired,
• Floristic surveys (cover and biomass) on 6 permanent plots and on specific stations,
• Topographical, sedimentological and hydrological surveys (piezometers and water level sensors) on the 6 permanent plots,
• Characterisation of the heterogeneity of the landscape on transects formed by dominos of 1 km² in the different zones,
• Assessment of the diversity of agricultural and parceling systems using remote sensing and available statistical data (graphical parcel register),

This work allows designing and testing ecological and agro-ecological indicators based on descriptions of the flora and landscape mosaics identified. The use of these different monitoring and analysis methods provides food for thought in the management of farms and landscapes, in the context of the removal of structures.

Laboratories involved

• SAD-Landscape, UR INRA/Agrocampus Ouest, Ecology department, Rennes
• ESE – UMR Ecology and Ecosystem Health, INRA/Agrocampus Ouest, Rennes
• LETG-Rennes-COSTEL – UMR Coastline, Environment, Remote sensing, Geomatics, Rennes