When Sheep And Shrub Make Peace On Rangelands: Linking The Dynamics Of Ruminant Feeding Behavior And Dominant Shrub Responses On Rangeland

After several decades of marginalization within farming systems, European rangelands are now being challenged to contribute to the conservation of ecological habitats and biodiversity. One of the main challenges, supported by the European Union incentives, relates to the reconciliation of livestock farmers' grazing practices and to the control of dominant plant dynamics, especially those of shrub species, which includes maintaining them at density levels appropriate for both habitat conservation and forage resources production. In this chapter, we aim to identify reasons for the difficulty in designing relevant management practices, with focus on the interlinkage of knowledge produced by animal sciences and plant population ecology. From the point of view of these two disciplines, we stress the importance of taking into account the reciprocal interactions between ruminants' foraging strategy and shrubs' demographic behavior. A series of results is given for our experiments on rangelands encroached by Scotch Broom shrubs (Cytisus scoparius L.Linck) and grazed by ewes. Considering the dynamics of ewes' behavioral patterns, we argue for a description of heterogeneous vegetation that recognizes feed items and their functionality for ruminants in maintaining their intake level in a fenced paddock. And considering the dynamic response of Scotch Broom shrubs to browsing, we also argue for demographic models that would recognize the importance of both the selective offlake of plant organs and the new browsing-induced demographic behavior of shrubs. These results enabled to identify the plant community as a mandatory intermediate object, and the plant organs as a key organization level at which these two processes interact. We propose an original conceptual framework that interlinks the two processes and recognizes the specific organizational levels and time frames. This framework should facilitate the identification of prospective research issues such as the differential impact of browsing on shrub demography according to plant organs and life stages consumed, or the effect of different vegetation states of a plant community on selective browsing among shrub organs. For rangeland management, the framework brings out the importance of greater precision in identifying the targets, and in particular the target plant organs and target life stages in shrub demography control. Considering this objective the choice of the season for grazing a given fenced pasture should also be made bearing in mind the global feeding offer within the plant community.