Patterns of Abundance in Grassy Vegetation of the New-England Tablelands; Identifying Regional Rarity in a Threatened Vegetation Type

Abstract

A survey of understorey species in grassy vegetation was conducted at 120 sites on the New England Tablelands (part of the northern tablelands of New South Wales), and the frequency of 371 taxa is presented. Very few species were common and the majority were recorded at < 5% of the sites. Similar patterns of abundance were also observed within the quadrats. Only 16% of taxa achieved dominance (i.e. > 10% canopy cover ) in any of the sampled quadrats, and while the average richness was 28 species (per 30 m²), the average number of dominant species per quadrat was only 1.6. The main dominants were perennial gasses. Of the native grasses thought to dominate this vegetation type at the time of European settlement, it would seem that Poa sieberiana has not declined. In contrast, Sorghum leiocladum and to a lesser extent Themeda australis appear to have declined. Although some native dicot species were very frequent, they rarely achieved dominance in the vegetation. These observations support the notion that sparseness may be a more common form of rarity than has been previously recognised.