We studied the long-term impact of wildfire on the vegetation
dynamics of sand grasslands in a forest-steppe vegetation mosaic
in Central Hungary (Kiskunság). Longterm permanent quadrat
monitoring was carried out from 1997 to 2008. We sampled the
forest-steppe mosaic both in burnt and unburnt areas in 100
patches altogether
using one by one meter quadrats. The effect of fire and
precipitation on vegetation dynamics was characterized by patch
type transitions between years. Patch types were defined by
means of Cocktail method. Nine patch types of sand grasslands
were altogether identified. The least productive patch types,
bare soil and cryptogam
dominance, did not occur in the burnt patches, while annual
dominated patch type appeared only in burnt patches. The
frequencies of patch type changes were significantly higher in
burnt patches than in unburnt ones, independently on the time
since fire. All the eight patch types found in the unburnt
patches proved permanent,
while in the burnt patches only four of seven were so. The
relative frequency of patch type changes did not correlate to
the precipitation in the vegetation period in the
unburnt patches, while positively correlated in the burnt
patches. It was concluded that the long-term difference in
grassland dynamics between the unburnt and burnt
patches, i.e. the excess of the patch type transitions in the
burnt grasslands, are due to increased drought sensitivity of
the grassland, which is the consequence of the elimination of
the woody component of the forest-steppe vegetation.
