Exploring the role of the diversity of herbaceous feed items for shrubby rangeland management

Biodiverse pasture ecosystems, such as rangelands, are now highly valued for their ecological, landscape and agronomic properties. The vegetation of these plant communities usually consists of a variety of herbaceous and shrubby species. Grazing and browsing by domestic herbivores has been proposed as an economic and efficient way to restore biodiversity and forage resource quality in herbaceous-shrub mosaics by, for example, avoiding shrub encroachment. Further, novel concepts in grazing science draw attention to the importance of maintaining functional heterogeneity in order to sustain food intake through behavioral adjustment. However, the challenge is now to define the heterogeneity, allowing integration of productive goals and the control of shrub dynamics in order to guide practices for rangeland management. Therefore, in this chapter, we aim to analyze the recent conceptual advances in the role of diverse vegetation on intake dynamics. We explore the foraging responses of ruminants faced with a diversity of herbaceous feed items and their effects on shrub (e.g. Cytisus scoparius Linck) consumption. We aim also to take into account the role of these feeding choices on intake dynamics at different time scales. Our approach is mainly based on experiments carried out in southern France on ewes grazing relatively small fenced paddocks for short periods of time in shrubby rangelands. Flock activities were always recorded through scan sampling method, and the ewes’ diet selection was encoded as bite categories. For instance, the effects of three different herbaceous covers with different forage availability and quality on shrub consumption were compared, mainly by showing how the availability of “herbaceous bites” and selection affect the way that ewes integrate shrubs into their diet. We also identify the behavioral adjustment possibilities between the size and quality of herbaceous vs. shrubby bites into meals. The results provide insights into ways to manipulate diet selection in order to stimulate the use of a dominant shrub by ewes. We highlight how grazing management of herbaceous physiognomy can lead to efficient shrub encroachment control. We discuss the usefulness of bite categories as functional feed indicators. Finally, operational implications are discussed in order to implement original approaches that take into account the functional interactions between ecological and technical processes. Adaptive management and its operational implementation are suggested as a promising approach.