Effects of guanaco dung piles on soil physicochemical properties in a shrub steppe of northeastern Patagonia

In arid and semi-arid ecosystems, soil resources tend to concentrate in vegetated patches, creating localized enrichment that contrasts with surrounding bare soil (BS). Guanaco (Lama guanicoe) dung piles in open areas of Patagonian shrub steppes could generate microsites that differ from this BS, yet how this localized input shapes soil properties and their spatial distribution at the landscape scale remains poorly understood. We analyzed the effects of dung piles on soil physicochemical properties and their potential landscape-scale influence in northeastern Patagonia. We sampled the center and edges of dung piles, adjacent BS, and plant patches (PP), measuring moisture, pH, electrical conductivity (EC), bulk density, carbon, nitrogen, and exchangeable cations (Ca2+, Mg2+, Na+, K+), and estimated dung-pile density across three plant communities differing in guanaco density. Soil moisture was lowest under PP, with no significant differences among the other microsites. Bulk density was lowest at the dung-pile center. EC was highest at the center but remained non-saline to slightly saline across all microsites. BS showed the highest pH, whereas soil beneath dung piles contained more carbon and nitrogen than BS, resembling PP. Mg2+ and K+ were highest at the dung-pile center, while Ca2+ and Na+ were highest in BS. Dung-pile density increased with guanaco population density, ranging from 261 to 2298 piles km−2 across communities. These results indicate that guanaco dung piles create distinct soil microsites that contribute to the spatial redistribution and heterogeneity of soil resources in this arid shrub steppe.