Pattern in Pleurophyllum herbfields on Macquarie Island (Subantarctic)

On Macquarie Island (54° 30′S, 158° 57′E), herbfields dominated by Pleurophyllum hookeri Buchan. typically occur on waterlogged peat soils from near sea‐level to approximately 340 m. They are also found on drained slopes; at higher altitudes on sheltered sites, and at lower altitudes as seral communities on screes and landslips. Pleurophyllum (Compositae), a relatively large‐leaved rosette plant, has features of both a geophyte and a hemi‐cryptophyte, and regenerates by both seedlings and axillary rhizomes. The herbfields are usually strongly patterned; the distribution of Pleurophyllum may be regular, random or clumped. The types of pattern are largely determined by the influence of environmental factors on the morphology and performance of both the dominant and other species. Drainage, exposure to wind, and temperature, as determined by altitude, are clearly important. The pattern is also strongly influenced by the balance between seedling and vegetative reproduction of the dominant species, and the outcome of competition with associated species, both vascular and cryptogamic. An extension to the basic method of pattern analysis, involving repeated analyses using only successively larger, older plants demonstrates that different age classes of rosettes show different scales of pattern. In the various types of pattern and process in these herbfields, Pleurophyllum may alternate with either Stilbocarpa polaris A. Gray, graminoids or bryophytes. There is no clear predictive relation between patterns as revealed statistically and the types of pattern and process.