Pyric herbivory in the northern mixed grass prairie: cattle habitat selection in response to prescribed fire

Background/Question/Methods

The grassland plant communities of the Great Plains of North America evolved with fire and bison grazing. Following settlement, the near extinction of the bison and fire suppresion fundamentally altered natural disturbance processes on the prairies. Fire disturbance creates a landscape that is variable in vegetation structure, composition, and biomass. Bison seek out recently burnt areas, leaving other areas on the landscape to recover from previous grazing. The attraction to burnt areas further promotes a heterogeneous landscape that varies in maturity, structure, and composition. Currently, cattle are the main source of grazing disturbance on native prairie and fire is rare. Cattle and bison are very different in their foraging preferences and social behaviours; with a resurgence in the use of prescribed fire on the prairies it is important to understand how cattle respond to fires. Here we examine the short-term effects of spring prescribed fires on both plant community structure and cattle habitat selection using a prescribed fire experiment in south-west Saskatchewan. Three spring prescribed fires were conducted and vegetation and the movement of GPS collared cattle monitored for two years post-fire.

Results/Conclusions

Prescribed fire reduced total plant and litter biomass, and combined with strong climatic influences on vegetation, resulted in significant seasonal and annual changes in biomass production. Burning homogenized vegetation composition in the growing season following the prescribed fire. Resource selection functions show a complex cattle response to the combined impacts of fire and year-to-year variation in forage ability. There was a significant increase in cattle usage of burned areas post-fire, but also major changes in useage of other parts of the landscape between years. These results demonstrate that pyric herbivory can be used as a livestock management tool in the northern mixed grass prairies of Canada.