Is the potential stability of forage resources under climate variability linked to transhumance patterns? An approach for sheep farming systems based on vegetation agroecological properties

Climate change, and in particular increased climate variability, is challenging the functioning of agro-pastoral livestock farms by impacting the availability of forage resources. Transhumant agropastoral systems, based on year-round herd mobility, mobilize a diversity of forage resources across time and space, which can potentially be a key factor in the stability of these forage resources in the face of climatic variability. This paper presents an original multiscale functional approach to evaluate the role of vegetation for forage resource stability in relation to herd mobility patterns (altitudinal and latitudinal gradients) in transhumant sheep systems (TSS) in the French Alps. We developed a set of indices that can provide information on forage stability at the farm level. These indices are based on (i) agro-ecological properties (based on the taxonomic and functional composition of vegetation) at the plot level combined at the farm level by the relative area of the plots and the distribution of the values of these indices, and (ii) the diversity of vegetation types within the farm. This approach was implemented on 12 sheep transhumant farms, representing a diversity of mobility gradients. We then measured the relationship between four categories of forage stability indices and herd mobility patterns. At farm level, we found positive correlations between the diversity of vegetation types and the range of altitudinal mobility, as well as between indices of distribution of vegetation functional characteristics (e.g., mean leaf dry matter content of plots) and the range of latitudinal mobility. Our results support the idea that differences in mobility gradients, whether along latitudinal or altitudinal gradients, provide access to different forms of complementarity that contribute to forage resource stability. However, our results also reveal trade-offs at the farm level between different dimensions of forage stability - particularly between productivity-related and those capturing plot's functional complementarity stability indices. Thus, forage resource stability in the face of climatic variability appears to be multidimensional, depending on the combination of different properties carried by the vegetation - no single indicator of forage potential stability prevails across all systems. Our framework highlights various pathways to forage resilience in a context of increasing climate variability. This multiscale methodology, combining functional indices and scaling-up processes, offers a transferable framework to assess resource stability. It can be applied beyond transhumant livestock systems and mobilized in research projects addressing the resilience of diverse socio-ecological systems under climate variability. • We assessed potential forage stability in transhumant sheep farms in the French Alps. • A hierarchical method was used, from vegetation types to the whole farmland. • Mobility gradients are linked to complementary forage resource use. • Different forage stability properties show trade-offs between each other. • Our framework highlights diverse pathways to forage resilience under increasing climatic variability.