Plant Ecology

, Volume 219, Issue 6, pp 649–663 | Cite as

Long-term grazing impacts on vegetation diversity, composition, and exotic species presence across an aridity gradient in northern temperate grasslands

  • Mark P. Lyseng
  • Edward W. Bork
  • Daniel B. Hewins
  • Mike J. Alexander
  • Cameron N. Carlyle
  • Scott X. Chang
  • Walter D. Willms


Little is known about the specific role of exotic species on measures of grassland plant diversity, including how this may vary with climatic conditions or large mammal herbivory. This study examined vegetation responses to long-term livestock grazing, including plant richness and diversity, as well as the contribution of exotic species to these metrics, across a network of 107 northern temperate grasslands in Alberta, Canada, spanning a broad aridity gradient. Exposure to grazing modestly increased plant richness, but did not alter Shannon’s diversity, Simpson’s diversity, or evenness, suggesting stability in floral diversity relative to grazing. However, grazing did increase grass cover while reducing shrub cover, the latter of which was only apparent in mesic grasslands. Unlike total plant diversity, exotic species richness and cover, together with exotic plant contributions to diversity, varied jointly with grazing and aridity. While long-term grazing increased exotic species, this response was most apparent in wetter areas, and non-grazed grasslands remained more resistant to the presence of exotics. Several exotic species were positive indicators of grazing in wetter grasslands, and coincided with lower native species cover, indicating grazing may be facilitating a shift from native to exotic vegetation under these conditions. Overall, our results indicate that while long-term grazing has altered the composition and cover of certain functional groups, including favoring exotics and minimizing woody vegetation in mesic areas, overall changes to plant diversity were limited. Additionally, these findings suggest that semi-arid northern temperate grasslands remain relatively resistant to grazing effects, including their susceptibility to exotic plant encroachment. These results improve our understanding of how ongoing grazing exposure may impact grassland diversity, including efforts to conserve native vegetation, as well as the important role of climate in altering fundamental grassland responses to grazing.


Aridity Exotic vegetation Long-term grazing Native grassland Plant diversity 



Funding for this project was provided by a Strategic Grant from the Alberta Livestock and Meat Agency, with additional support from Alberta Environment and Parks. We are grateful to the numerous AEP staff, specifically Kevin France, Craig Demaere, Jennifer Richman, Laura Blonski, Tennille Kupsch, Terri France, Darlene Moisey, Barry Adams, Tanner Broadbent, and Mike Willoughby, for allowing access to the Rangeland Reference Areas and helping with data collection. We also thank the following individuals for technical field assistance: Mark Donner, Ian Brusselars, Donald Schoderbek, and Leah Rodvang, and special thanks to Sarah Green for assisting with the graphics.


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Copyright information

© Springer Science+Business Media B.V., part of Springer Nature 2018

Authors and Affiliations

  1. 1.Alberta Environment and Parks, Government of AlbertaEdmontonCanada
  2. 2.Department of Agriculture, Food and Nutritional ScienceUniversity of AlbertaEdmontonCanada
  3. 3.Biology DepartmentRhode Island CollegeProvidenceUSA
  4. 4.Alberta Environment and Parks, Government of AlbertaLethbridgeCanada
  5. 5.Department of Renewable ResourcesUniversity of AlbertaEdmontonCanada
  6. 6.Agriculture and Agri-Food Canada (Retired)LethbridgeCanada

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