Habitat islands in fire-prone vegetation: do landscape features influence community composition?

Aim Landscape features, such as rock outcrops and ravines, can act as habitat islands in fire-prone vegetation by influencing the fire regime. In coastal and sub-coastal areas of Australia, rock outcrops and pavements form potential habitat islands in a matrix of fire-prone eucalypt forests. The aim of this study was to compare floristic composition and fire response traits of plants occurring on rocky areas and contrast them with the surrounding matrix. Methods Patterns of plant community composition and fire response were compared between rocky areas and surrounding sclerophyll forests in a range of climate types to test for differences. Classification and ordination were used to compare floristic composition and univariate analyses were used to compare fire response traits. Results The rock outcrops and pavements were dissimilar in species composition from the forest matrix but shared genera and families with the matrix. Outcrops and pavements were dominated by scleromorphic shrubs that were mainly killed by fire and had post-fire seedling recruitment (obligate seeders). In contrast, the most abundant species in the adjacent forest matrix were species that sprout after fire (sprouters). Main conclusions Fire frequency and intensity are likely to be less on outcrops than in the forest matrix because the physical barrier of rock edges disrupts fires. Under the regime of more frequent fires, obligate seeders have been removed or reduced in abundance from the forest matrix. This process may have also operated over evolutionary time-scales and resulted in convergence towards obligate seeding traits on outcrop fire shadows. In contrast, there may have been convergence towards sprouting in the forest matrix as a result of selection for persistence under a regime of frequent fire.