Burnt to blazes: landscape fires, resilience and habitat interaction in frequently burnt coastal heath

Abstract

Four fires burned vegetation on a sand plain on a 4-km stretch of Pleistocene beach ridges between 1980–1981 and 1998. Fires of 1980–81 and 1991 burned the whole area. Those of 1994 and 1998 burned only parts of it. Cover of individual species and bare ground was scored on permanent plots at intervals between 1990 and 1996. Ordination and generalised linear model analysis of the data showed strong spatial variation between dry and wet heaths, four transects and plots within transects. This was strictly conserved through time, owing to the rapid regrowth of abundant resprouting species, most of which, after 1 year, showed little change in cover with increasing time-since-fire. Vegetation of the dry and wet heaths showed no detectable convergence or divergence in similarity with time-since-fire or variation of interval between fires. Changes with time-since-fire were found, and some change with the length of fire interval, owing to variation in cover of obligate-seeder species, which increased steadily with time up to 10 years since fire, and showed some decrease when fire interval decreased to 3.75 years. At 10 years since fire, obligate-seeder species reached ~25% of the totalled cover scores for all species, with 75% from resprouting species. Dry and wet heath were broadly similar in their general pattern of regrowth after fire, but in dry heath bare ground was more slowly covered than in wet heath, and wet heath had a higher cover of monocotyledons, especially restiads and sedges. Wet heath was more flammable than dry heath in the patchy fire of 1998. The heaths observed appeared highly resilient to recent fire regimes. Resprouting species always dominated their canopy; none of their obligate-seeding species formed a dominant overstorey canopy.