Friday, August 8, 2008 - 9:50 AM

COS 112-6: Pyric herbivory: Changing selectivity

Brady W. Allred, Oklahoma State University and Samuel D. Fuhlendorf, Oklahoma State University.


Fire and grazing are recognized as inherent and critical disturbances in the maintenance of grasslands.  While extensive research of these subjects has focused on their effects as independent forces upon the landscape, the spatial and biological interaction of the two has received less consideration.  Fire and grazing interact through positive and negative feedbacks to create shifting mosaics of vegetation patterns across the landscape.  The pyric herbivory model integrates fire and grazing, allowing for examination of the complex relationships created by both disturbances and their interactions.  Grassland birds, invertebrates, and plant biodiversity respond to the differing plant assemblages created by fire and grazing.  Recent studies have shown that interactions created by fire and grazing alter the behavior of grazing animals.  To determine how pyric herbivory alters the selectivity of grazing ungulates, we studied animal behavior through movements tracked by global positioning systems.


Animals spent 62% of their time in areas that were recently burned.  Selectivity was altered when fire was applied to discrete portions of the landscape in a patchwork fashion, with animals selecting at larger patch sizes than when fire was applied uniformly.  Burned patches also affected foraging behavior and distance traveled.  Animals in patch burned habitat traveled further than animals in uniformly burned areas.  This and other research suggests that fire and grazing are inherently linked.  The biological interactions created by both disturbances should be taken into account when conducting grassland research.