How Transhumance and Pastoral Commons Shape Plant Community Structure and Composition

Human practices and local governance effects on plant communities is a major question in socio-ecological sustainability. Pastoralists’ practices are intricately linked to governance systems and to their social-ecological context. For example, spatial-temporal mobility arises as a means to cope with seasonal variability of forage mass. This mobility might deeply influence plant biodiversity in rangelands by changing the ratio of perennial and annual life-forms. This study focuses on the commonly governed high-altitude rangelands of Castril, Santiago and Pontones (CSP) in North-Eastern Andalusia (Spain). CSP are grounded on three pastoralist communities who have self-organized into three different governance systems, that of Castril, Santiago and Pontones, for the use of three contiguous rangelands through extensive and transhumant grazing. Pastoralists undertaking Short-Distance Transhumance (SDT) or Long-Distance Transhumance (LDT) arrive on the CSP summer rangelands in early May and June respectively. We aim to identify plant community types within CSP to unravel the effect of community-based governances found in these three commons and the impact of the different transhumance types (SDT vs. LDT) on the plant community structure and composition. For this, during spring 2022 and 2023, we carried out 72 vegetation transects (point-contact monitoring methodology) spread in Castril, Santiago and Pontones encompassing the transhumance modalities. Plant data were analyzed through a Non-metric MultiDimensional Scaling (NMDS) ordination based on Bray-Curtis dissimilarity index. NMDS results revealed variability within the plant community distinguishing between perennials and annuals which belong to different phytosociological classes. This variability was partially related to transhumance modalities with LDT areas showing high density of perennials, whereas SDT areas showing high density of annuals belonging to the Tuberarietea-guttatae phytosociological class. Our findings suggest that LDT areas may provide more forage mass than SDT areas during summer drought.