Grazing effects on vegetation composition and on the spread of fire on open sand grasslands

We studied the effects of sheep [Ovis aries (L.)] and rabbit [Oryctolagus cuniculus (L.)] grazing on the spread of induced fire on an open sand grassland community in the Hungarian Plain. Patches of open sand grassland were grazed by sheep in April and by sheep and rabbit in May of 2003. Half of each patch was burned in July. Canopy cover of the litter and vascular plant species, species number, plant height, burnt area, and the speed of fire-spread were estimated in 1 x 1 m quadrates. The burnt area was significantly smaller with late sheep grazing, while the speed of fire-spread decreased significantly due to rabbit grazing compared to that of the control. Plant height was significantly decreased by early and late sheep grazing, while rabbit grazing resulted in significantly lower canopy cover values of vascular plants compared to the control. Early sheep grazing resulted in overcompensation of the canopy cover of vascular plants. Species number was not affected by the grazing treatments. This 1-year experiment demonstrated that moderate grazing has no short-term effects on the species diversity of the semi-arid open sand grassland. Furthermore, late spring grazing decreased the spread of fire on the grassland portions of the community; thus it may inhibit the burning of large areas of the semi-arid forest-steppe.