Shrub encroachment in semi-arid rangelands of southwestern Buenos Aires, Argentina does not affect plant diversity and composition

Abstract

Shrub encroachment in semi-arid rangelands is a phenomenon associated with changes in floristic composition, loss of diversity and ecosystem degradation, enhanced by inappropriate grazing practices. However, the outcome depends on the species' identity and the management carried out. The objective of this study was to evaluate shrub species dynamics and their effect on plant community composition in a Monte rangeland of Argentina, under conservative grazing management at two different working scales. During two years, ground-based vegetation and soil cover measurements were performed in patches with and without shrubs using Daubenmire and Canfield's methods. Herbaceous and woody species recorded were classified according to their functional traits and forage value. Specific richness, Shannon's diversity index and Pielou's evenness were calculated. At a larger-scale evaluation, Sentinel-2A satellite images from year 2016–2022 were classified into three cover classes to evaluate the shrub encroachment process. Although an increase in shrub presence was observed over the years at both scales no effect was found on the diversity and specific composition, nor on the occurrence of forage species. Shrub presence promotes the coexistence of species with different functional traits and creates favorable conditions for soil protection and the establishment of desirable species for livestock purposes.