A framework for testing the influence of Aboriginal burning on grassy ecosystems in lowland, mesic south–eastern Australia

The complex interactions among climate, soils, fire and humans in the biogeography of natural grasslands has long been debated in Australia. On the one hand, ecological models assume the primacy of climate and soils. On the other, Aboriginal burning is hypothesised to have altered the entire continent since before the last glacial maximum. The present paper develops a framework to test for the ‘fingerprint’ of Aboriginal burning in lowland, mesic grassy ecosystems of south-eastern Australia, using ecological theory, and the ethno-historical record. It is clear that fire-stick farming was used to promote staple roots in south-eastern Australia and, in some instances, it has been shown to influence grassland–woodland boundaries. The framework comprises the following three evidence lines: (1) archival benchmarking and palaeoecology; (2) phytoecology; and (3) ethnology and archaeology. That fire-stick farming was likely instrumental in grassland formation and maintenance must be supported by evidence that shows that ‘natural’ grasslands exist in climatically–edaphically unexpected places, that fine-scale patterns and dynamics are at least partly due to fire and that the fire regime has been influenced by Aboriginal burning. Application of the framework indicated that widespread Aboriginal burning for staple foods likely extended the area of temperate grasslands and influenced their structure and function.

Cause and effects of a megafire in sedge-heathland in the Tasmanian temperate wilderness

The World Heritage wilderness of south-western Tasmania contains a complex vegetation mosaic of eucalypt forest, myrtaceous scrub and fire-sensitive rainforest embedded in highly flammable sedge–heathland. Aboriginal burning shaped this temperate region for millennia, and large, severe wildfires have prevailed since European settlement in the early 19th century. In 2013, the Giblin River fire burnt 45 000 ha of wilderness, most of which was sedge-heathland. We surveyed the fire footprint, and an adjacent management burn, to investigate the drivers of fire severity in sedge-heathland and to assess the regeneration response of woody vegetation and how these were influenced by antecedent fire histories. Analyses based on multi-model inference identified time since fire as the most important driver of sedge-heathland fire severity, as measured by diameter of burnt twigs. Mortality was high for both main stems (98%) and whole plants (91%), with only 16% of dead stems resprouting. Resprouting and seedling establishment were little affected by fire severity. The value of prescribed burning in reducing both the extent and severity of wildfires in the south-western Tasmanian landscape, and in maintaining stand-age heterogeneity, is illustrated by the wildfire having self-extinguished on the boundary of the management burn.

“Careless fires” and “smoaky weather”: The documentation of prescribed burning in the Peace–Athabasca trading post journals 1818–1899

An examination of a series of trade post journals from northern Alberta shows how the recording of prescribed fires was shaped by the foci of these brief journal entries. Contextual analysis of these records informed by previous ethnographic research on local Aboriginal burning suggests 1) that prescribed fires that were both routine and carried out at some distance from the post were not likely to be recorded, and 2) that the Aboriginal “careless fires” that threatened or appeared to threaten post property were in fact prescribed fires.

Two Hundred Years of Land Use and Vegetation Change in a Remnant Coastal Woodland in Southern Australia

Post-settlement changes in vegetation and land use were examined in a reputedly undisturbed woodland remnant at Ocean Grove, southern Victoria, the site of earlier ecological studies. The vegetation has passed through at least three structural phases since European colonisation: an open grassy woodland dominated by Allocasuarina and Eucalyptus species and Banksia marginata Cav. with few shrubs; an open scrub of Acacia pycnantha Benth.; and a closed scrub of Allocasuarina littoralis (Salisb.) L.A.S.Johnson, which now dominates the reserve. Tree and shrub density has progressively increased, from perhaps less than 20 trees ha–1 in the early 1800s, to over 3000 trees ha–1 in 1996. Most large Allocasuarina trees established in the late 1930s or early 1940s, and Allocasuarina littoralis appears to have invaded rapidly thereafter. Surprisingly, A. littoralis was not recorded in an 1894 plant census, and might have been locally rare last century. Vegetation changes over the past 200 years can be attributed to the long-term absence of fire. The abundant recruitment of Acacia species in the mid- to late-1800s may have been a rapid response to the curtailment of Aboriginal burning, and the more recent invasion of A. littoralis a longer-term response to fire exclusion. The importance of active vegetation management for biodiversity conservation in the future is stressed.