Pyric herbivory
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Pyric herbivory is the term for the interactions of fire with grazing on a grassland.[1] These interactions can promote biodiversity and function of grasslands.[1] Fire will increase the amount of grazing in a certain area, as grazing herbivores prefer the nutritious forage available in recently burned areas.[1][2] Since herbivores do not prefer areas that have not been recently burned, fuel will accumulate in unburned areas.[2] This causes those areas to burn more easily in the future.[2] These interactions between fire and grazing across space and time are referred to as positive and negative feedbacks.[1] These interactions create heterogeneity across the landscape.[1][2][3] Pyric herbivory is important to ecosystems that have evolved with fire and grazing, such as grasslands.[4]
Mechanisms
Pyric herbivory occurs because burning produces early successional plants that are more palatable and nutritious than late successional plants.[1] Because of this, herbivores prefer the forage that grows in recently burned areas.[1] Herbivores will graze more in the recently burned areas, causing leaf litter to build up in unburned areas.[1] This makes the unburned areas more prone to fire in the future.[1] Once fire occurs in a new area, herbivores will start grazing in that area.[1][2] This creates shifting patterns of grazing and fire across the landscape.[2]
Ecological importance
The shifting patterns of heterogeneity that are created by pyric herbivory changes the number and type of plant species present in the area.[2] This supports biodiversity of plants and wildlife in the area, restores and maintains ecosystem function, and aids in nutrient cycling.[1][2][3] It especially increases the availability of nitrogen and phosphorus by converting litter into ash.[3] A lack of disturbances such as fire and grazing can decrease biodiversity and soil function quality, as well as allow for woody encroachment.[3][5]
Concerns
There is a concern that agricultural livestock production will not be maintained when using conservation management strategies because of a need to lower stocking rates.[6] Pyric herbivory is a strategy that allows landowners to maintain stocking rates without losing livestock productivity and also improve the health of the grassland.[6]
There are social factors involved in whether a landowner chooses to implement pyric herbivory.[5] These factors include previous experience of the landowner, the landowner's perception of woody encroachment on the land, proximity to neighbors, and risk orientation.[5] Previous experience applying pyric herbivory will increase the landowner's likelihood to apply it as a management strategy.[5]