In arid US rangelands, riparian areas generate a suite of ecosystem functions and services important to wildlife and people. For example, riparian ecosystems provide season-long livestock forage and habitat for species of interest such as sage-grouse. These areas are also expected to maintain water quality that meets state and federal thresholds. Due to the multi-use mandate on public lands, managers are tasked with balancing these different demands. One solution is to manage the duration of grazing. This can alter cattle disturbance of stream-side vegetation and limit waste inputs into streams. To test whether grazing can be managed to increase the provision of multiple ecosystem services, we conducted a two year study (2016-17) that examined the effects of different grazing strategies on water quality (E. coli levels (MPU/100 ml)), sage-grouse habitat (stubble height (cm)), and stream-bank stability (% bare ground). The grazing systems investigated included those commonly employed in our study area: continuous turnout (cattle present for 4 months), 4-pasture rotation (1.5-2 months), and rapid-rotation (2-4 weeks). We measured water quality along 11 rangeland streams via grab samples collected twice monthly from May - November, and stubble height and erosion potential along nine streams assessed monthly from May – August.
Results/Conclusions
We found that controlling the duration of grazing in Intermountain West rangelands is an important tool for managing multiple riparian ecosystem services. Cattle presence directly affected water quality, with E. coli levels increasing when cattle entered pastures and declining after they left. Rapid grazing rotations and shorter grazing durations resulted in fewer violations of Utah and EPA critical water quality thresholds. Grazing duration also directly affected stubble height and % bare ground. Longer grazing durations (both continuous turnout and 4-pasture rotation) led to more disturbance than rapid-rotation. This was evidenced by shorter stubble height, which early in the season can reduce sage-grouse habitat quality, and more bare ground, which can lead to stream-bank erosion. Grazing strategies that included rotation (both 4-pasture and rapid-rotation) were accompanied by vegetation re-growth once cattle were removed. This suggests that although active grazing can negatively affect all ecosystem services studied, moving cattle can allow ecosystem services to recover. Overall, we find that when the disturbance caused by grazing is limited by cattle rotation, livestock production can be balanced with the provision of a suite of ecosystem services such as water quality, maintenance of sage-grouse habitat, and stream-bank stability.