Biogeochemical and ecological impacts of livestock grazing in semi-arid southeastern Utah, USA

Relatively few studies have examined the ecological and biogeochemical effects of livestock grazing in southeastern Utah. In this study, we evaluated how grazing has affected soil organic carbon and nitrogen to a depth of 50 cm in grasslands located in relict and actively-grazed sites in the Canyonlands physiographic section of the Colorado Plateau. We also evaluated differences in plant ground cover and the spatial distribution of soil resources. Results show that areas used by domestic livestock have 20% less plant cover and 100% less soil organic carbon and nitrogen compared to relict sites browsed by native ungulates. In actively grazed sites, domestic livestock grazing also appears to lead to clustered, rather than random, spatial distribution of soil resources. Magnetic susceptibility, a proxy for soil stability in this region, suggests that grazing increases soil erosion leading to an increase in the area of nutrient-depleted bare ground. Overall, these results, combined with previous studies in the region, suggest that livestock grazing affects both plant cover and soil fertility with potential long-term implications for the sustainability of grazing operations in this semi-arid landscape.