Grazing cattle maintain the integrity of northern fescue prairies invaded by Kentucky bluegrass: Case study from Batoche National Historic Site of Canada

Background/Question/Methods Northern fescue prairies, once common in the Aspen Parkland Ecoregion of western Canada, have become increasingly lost to agricultural expansion and the proliferation of exotic species. Despite these pressures, northern fescue prairies remain important to the management of wildlife, conservation of species at risk, and the provision of ecosystem services. In this project, we determine whether Kentucky bluegrass (Poa pratensis subsp. pratensis), an exotic species introduced across the Great Plains, poses a threat to plains rough fescue (Festuca hallii). We also examine whether grazing by cattle can help in the restoration of northern fescue prairies. Between 2006 and 2009, we randomly selected 23 patches of prairie inside Batoche National Historic Site, in Saskatchewan. Using 34 transects (44 m), we recorded the frequency of Kentucky bluegrass and plains rough fescue inside 15 quadrats (75 x 75 cm), placed at 3 m intervals along each transect. We also used six exclosures to examine the impact of cattle grazing on the frequency of these species.

Results/Conclusions Higher densities of Kentucky bluegrass were negatively correlated with the density of plains rough fescue (R² = -0.439). Despite its invasiveness, the abundance of Kentucky bluegrass declined in the presence of cattle grazing (16.6 ± 3.2 plants/m² vs. 9.4 ± 3.4 plants/m²). In contrast, grazing did not impact the density of plains rough fescue (1.6 ± 1.8 plants/m² vs. 1.4 ± 1.4 plants/m²). Our results illustrate that, in the presence of exotic invaders, the conservation of northern fescue prairies requires active methods of restoration. Based on our observations, grazing by cattle provides one tool to actively manage and restore the integrity of northern fescue prairies invaded by Kentucky bluegrass.