EFFECTS OF 4 LOW-INTENSITY BURNS OVER 14 YEARS ON THE FLORISTICS OF ABLACKBUTT (EUCALYPTUS-PILULARIS) FOREST IN SOUTHERN QUEENSLAND

A grassy open forest of Eucalyptus pilularis Smith, E. saligna Smith, and other eucalypts, with an understorey of Allocasuarina torulosa (Ai ton) L.A.S.Johnson and Acacia spp., was studied by belt transect for 1 4 years. The forest, north of Toowoomba in Queensland, was divided by a fire break into a non-burned section and a section that had a low-in tensity prescribed burn through it four times over the observation per iod. Cover of herbaceous species, measured with the intercept method, and density of perennial species were recorded six times in the burned section and seven times in the non-burned section over the observatio n period. There was no difference between burning treatments in cover or density of the species sampled nor in their diversity (Shannon inde x) over this period. Classification analysis of data sets of the whole transect did not show clear groups and ordination of these data sets produced axes related to distribution of major species. These analyses indicated spatial variability along the transect as was apparent in t he field. Total cover of the main grass species confirmed this variabi lity, but also showed changes in parts of the transect over the period that were ascribed to changes in cover of the shrub layer. Data sugge sted that low-intensity burning stimulated ecesis of Acacia spp. but d id not affect density of Allocasuarina torulosa (Aiton) L.A.S.Johnson and young eucalypts in this forest. Burning kept Lantana camara L. bus hes small compared with not burning. Covers of the major grasses, Micr olaena stipoides (Labill.) R.Br., Themeda triandra Forssk and Imperata cylindrica (L.) Rauschel, were not different between burning treatmen ts. It appears that low-intensity prescribed burning produced less cha nge over the 14 year period than did no burning. Change in the non-bur ned section may be attributed to encroachment of the exotic species La ntana camara. This situation is discussed in relation to recent plant succession theory.