In the Patagonian drylands, extensive sheep production coexists with guanaco, the most abundant native herbivore. While sheep’s impacts on vegetation are well known, guanaco effects remain poorly understood, limiting effective management. We evaluated the influence of both species on grassland regeneration at two representative sites by comparing areas grazed by sheep or guanaco and applying short-term herbivore exclusions. We analyzed pre- and post-dispersal soil seed banks in vegetated patches and bare soil, and measured seedling emergence and tiller production of dominant perennial grasses. The soil seed bank was dominated by annual species, and vegetated patches showed higher perennial abundance after seed dispersal, but no significant differences emerged between herbivores. Seedling emergence was similar for sheep and guanaco, increasing notably after short-term exclusion. However, perennial grass regeneration through tillering responded differently: guanaco exclusion enhanced tillering of Nassella tenuis and Pappostipa speciosa, whereas sheep exclusion produced no significant effect. Overall, most regeneration mechanisms showed comparable patterns under both herbivores. These findings suggest that, although guanaco and sheep exert similar pressures on seedling dynamics, guanaco grazing may differently affect perennial grass recovery. We emphasize the need for careful monitoring of guanaco stocking rates to ensure sustainable management of Patagonian shrub-steppe ecosystems.

Grasslands are one of the major ecosystem types in drylands. Encroachment of shrubs into grasslands affects the functioning of drylands by altering community structure, with impacts exacerbated under greater intensity of encroachment. Yet, we have a limited understanding of how ecosystem structure responds to the degree of shrub encroachment. Here, we describe a field-based study designed to examine changes in ecosystem structure beneath shrub patches (patch condition) and between patches (spatial distribution pattern of patches) along a gradient in encroachment in a semiarid grassland in Inner Mongolia, China. We found that greater encroachment was associated with wider and taller shrubs with more branches. As shrub encroachment intensified, the area beneath shrubs had more litter and was less exposed to grazing. The landscape was characterized by more discontinuous patches of vegetation and more bare ground as encroachment intensified. Either the patch condition or the patch spatial pattern was shaped mainly by the magnitude of shrub encroachment rather than by the structure of individual shrubs (e.g., height and canopy width). Our study highlights the idiosyncratic response of ecosystem structure (patch condition and patch spatial pattern) to intensifying encroachment, reinforcing the importance of considering the degree of shrub encroachment when managing encroached grasslands.