Plant dispersal mediated by sheep pastoralism on the banks of the Loire River - DISPERSAL

Objectives

Some of the benefits associated with pastoralism have been well identified, but the risks linked to the spread of non-native plants are less well known. The DispersaL Project will first compare how the different stakeholders view the advantages and drawbacks of sheep pastoralism on natural habitats, flora and entomofauna within the heritage landscapes of the Val de Loire. Ecological studies concern grazing sites on the banks of the Loire River. We will be looking at the material carried by the Loire River and how it is affecting different floral compartments: the soil seed bank, the flora expressed, and the plants grazed and dispersed by sheep. We will study the coprophagous insects associated with pastoralism that are involved in the recycling of organic matter and in secondary seed dispersal. We will also assess the consequences of grazing on the endo- and epizoochorous dispersal cycle of native and non-native plants at successive grazing sites. These in situ observations will be completed by an experiment under controlled conditions designed to test the effect of animal sociality on zoochorous dispersal. Finally, the results obtained will help managers to readjust pastoral practices (residence time, composition of the sheep flock) according to the processes that determine floral diversity, flock management and economic profitability.

Approachs

The grazing sites on the banks of the Loire River are located in at Bonny sur Loire and Briare, and extend over a distance of 9 km. Heritage sites such as the Mantelot canal locks and the Briare canal-bridge are nearby. We will interview different actors in the direct vicinity of the grazing sites to clarify the local perception of the ecosystem and to identify the social and economic issues at stake.

We will carry out botanical inventories on the grazing sites to monitor the plant species present and those that are consumed. The experimental design will include pairs of 1m² quadrats, some protected from animals (within wire cages) and others accessible, coupled with camera traps attached to a sub-sample of the wire cages to assess grazing frequency by both sheep and wild ungulates. Pitfall traps baited with sheep faeces will be used to capture dung beetles and determine the assemblages present. We will collect faeces and fleece (from shearing) from different individuals to identify and quantify the seeds dispersed via endo- and epizoochory. In addition, we will conduct an experiment to test the effect of animal sociality, in this case the composition of the group (lambs and ewes), on seed dispersal distances and seed deposition patterns.

Participants

INRAE units involved

• UR EFNO
• UE P3R (small ruminant phenotyping centre)

Partnership

• Conservatoire d'espaces naturels Centre-Val de Loire
• INSA Centre-Val de Loire - UMR CITERES
• Université d'Angers - Biodiv'AG
• Laboratoire d'éco-entomologie (bureau d'études)