The ecology of granite outcrops at Wilson's Promontory, Victoria

Abstract

AbstractRock outcrops on spurs and summits on Wilson's Promontory tend to be more prevalent on hot dry slopes than cool moist ones. In this comparatively moist climate, the rock outcrop vegetation can be grouped into high altitude, low altitude and coastal types. The surrounding rock‐heath is characterized below 400–500 m by Kunzea ambigua and above this altitude by Callistemon pallidus. Moss aprons of Campylopus bicolor on rock faces are often held in place by roots of surrounding shrubs on slopes up to 20°. Bryophyte and lichen communities vary with altitude, and annuals and geophytes are common. Fire may result in retrogression if forests and shrub zones are destroyed and humic top soil burnt or eroded away. Fossil root‐grooves occur in granite on the summit of Mt Latrobe and are the legacy of a cloud forest of Nothofagus cunninghamii. The rock‐heath species are more drought resistant than the‘climax’tree species and may develop very low water potentials. The rate of succession may be correlated with the highly variable rate of decay of each individual block of granite.The soils of the early successional stages are veneers of humic sands enriched with hill‐wash, whilst the soils of the forest stages vary from duplex podzols to gradational podzolic soils of much greater moisture storage. Woody plant establishment is mostly initiated along rock joints: the rock surfaces and boulders so by‐passed are colonized by more mesic species. Many zonations appear to be static since advances are cancelled by retreats.The rate of succession on bare granite is controlled by local climate, altitude, slope, fire and macro‐and micro‐jointing patterns. In general, the early stages bear strong similarities over a relatively wide range of climate. The so‐called climaxes which have developed represent a continuum in response to the complex environments found on Wilson's Promontory.