Open Access

J. S. Cohn, Ross A. Bradstock, S. Burke

• In 1985 and 1989, two studies examined the effects of time since fire, topography and resprouting eucalypts on the composition of understorey species in mallee vegetation at Yathong Nature Reserve, in semi-arid New South Wales. Emphasis was on ephemerals. Species richness was significantly higher at 2.5 years after fire. Species present five years after fire were a subset of those occurring earlier. Twodimensional ordination based on ranked similarity measures of species and analysis of similarities indicated discrete time since fire groups. Short-lived species dominated early groups (< 2.5 years) i.e. Haloragis odontocarpa, Convolvulus erubescens, Sclerolaena parviflora and Solanum coactiliferum. All these species had disappeared at > 5 years. The perennials Triodia scariosa, Amphipogon caricinus and Halgania cyanea, dominated at > 5 years post-fire. Species composition was significantly affected by topographic position (upper, mid, lower dune) but not by mallee eucalypts (under canopy, in gap). Two-dimensional ordination based on ranked similarity measures of species and ANOSIM indicated that upper and lower topographic positions were significantly different. Most common species in upper topographic positions were Haloragis odontocarpa, Bracteantha viscosa and Sclerolaena parviflora and in the lower Stipa scabra, Haloragis odontocarpa and Chenopodium sp. Species richness was not significantly affected by topography or eucalypts (17.45/10m2 +/- 0.16). The number of ephemeral species (10 m-2) was higher in the lower topographic positions (7.87 +/- 0.66) than the upper (4.88 +/- 0.44). There was no significant effect of eucalypts on the number of ephemeral or perennial species.