The effect of serpentine on vegetation structure, composition and endemism in northern New South Wales, Australia

Serpentine rocks occupy less than 1% of the area of New South Wales, Australia, existing as isolated outcrops. The degree of endemism of the serpentine vegetation is high. The serpentinite outcrop at Baryulgil in the humid climate of northeastern NSW is one of a string of such outcrops along the eastern seaboard of Australia, but is spatially isolated. A comparative study of the vegetation of the serpentinite at Baryulgil with that of the adjacent sandstone and granite, on sites with both northerly and southerly aspects, shows that the vegetation structure and composition on the serpentinite differs significantly from that on the other substrates. The species composition of the Baryulgil serpentine vegetation is distinct. Its height, basal area, and overstorey cover are low, and there is no variation in the structure and biomass of the vegetation with aspect. The overstorey of the serpentine vegetation is dominated either by Eucalyptus acmenoides and E. ophitica or by Allocasuarina torulosa. Eucalyptus ophitica is endemic to the Baryulgil serpentinite outcrop. The suppression of vegetation development on the serpentinite in comparison with other substrates does not appear to be attributable to either nutrient deficiency (as evidenced by phosphorus levels) or to levels of potentially phytotoxic elements.