Heavy grazing over 64 years reduced soil bacterial diversity in the foothills of the Rocky Mountains, Canada

In the foothills of the Rocky Mountains, rough fescue grasslands are primarily managed for cattle grazing. Yet, the effect of long-term cattle grazing on the soil bacterial community and their relationship to soil properties is uncertain. This research took advantage of a long-term grazing study that was established near Stavely, Alberta, Canada in 1949 to assess how more than six decades of different cattle stocking rates (Mid-May to Mid-November) effected the soil bacterial community and their relationship with soil properties. We found that heavy grazing, roughly three times the recommended cattle stocking rate, clearly shifted the bacterial community composition and led to reduced bacterial diversity. Meanwhile, moderate grazing, slightly above the recommended cattle stocking rate, shared a similar bacterial community composition as the section of grassland that was fenced off and excluded from grazing since the beginning of the experiment. Further analyses revealed that the effect of grazing largely depended on how the intensity of grazing altered soil properties. Overall, grazing for more than six decades, at moderate cattle stocking rates, should not be expected to change the soil bacterial community composition in the foothills of the Rocky Mountains, Canada. This information will provide grassland managers with valuable information about how soil biodiversity responds to long-term grazing. The long-term nature of this field experiment is a similar reality faced by many beef producers.