A fine‐resolution Pliocene pollen and charcoal record from Yallalie, south‐western Australia

Abstract

Aim This paper aims to reconstruct a high‐resolution fire and vegetation history from a period when humans were absent in Australia. This is then used to comment on the frequency of natural fire in high biodiversity heathland, and to compare this with historical fire regime in the same region. Methods A section of varved sediment covering a period of c. 84 years was taken from Palaeolake Yallalie in south‐western Australia. The sediments were separated into approximately single to small multiples of years and then analysed for charcoal, pollen and sediment analysis to reconstruct the environmental conditions at the time. Results The charcoal record indicates fire recurrence to have been roughly between 5 and 13 years, a little longer than those of the historical period. The pollen record was dominated by Casuarinaceae, Myrtaceae and a large number of Proteaceae species; these are intermixed with Araucariaceae, Nothofagus and Podocarpus. This suggests there was a mix of sclerophyll woodland and a mosaic of rain forest elements, thus conditions must have been wetter, particularly in the summers, compared with today. Conclusions We assume that fire was most likely confined to the sclerophyll vegetation, and that fire has been a significant feature of the environment long before humans entered Australia. The slightly longer fire recurrence times compared with the present result from the intermittent nature of lightning and wetter summers at the time.

Post‐fire regeneration of Mediterranean plant communities at a regional scale is dependent on vegetation type and dryness

“…Although fire recurrence intervals in some mediterranean type regions are shorter (e.g. 4-45 years in South African fynbos, van Wilgen et al 1992avan Wilgen et al , 1992b3-13 years in Australian heathlands, Atahan et al 2004), the time without fire interval in the study sites is not particularly large in comparison to the periods described for the Californian chaparral (ca. 70 years, Minnich 1983;Minnich & Chou 1997) and, especially, the Mediterranean basin (mean interval of 133 years according to Díaz-Delgado et al 2004), which has a fire frequency considerably lower than other Mediterranean regions (Lloret et al in press).…”

Estimating the age of fire in the Cape flora of South Africa from an orchid phylogeny

“…The first positive charcoal evidence of fires in southwestern Australia dates back to the mid-Pliocene. Atahan et al [61] documented that 3.15 Ma deposits from Yallalie, showing a mix of heath and sclerophyll woodland with some remaining rainforest elements, had a fire frequency of between 5 and 13 years. No information on the age of fire regime in the Cape fynbos exists [13].…”

An Early Holocene Palaeoenvironmental Record from Two Mile Lake, South‐Western Australia

“…This equation has been used to calibrate fossil pollen studies in south-western Australia (Atahan et al 2004;Itzstein-Davey 2004). Here, the equation indicates that the number of Proteaceae species growing in the vegetation during the Holocene around Two Mile Lake was estimated to be between 7.6 and 8.65 species, that is approximately eight species (Table 4).…”

“…Proteaceae species are an important component of the south-western Australian vegetation in terms of species number and their role in vegetation structure (George 1998). This prompted an integrated study investigating the development of the Proteaceae over the Cainozoic from fossil pollen studies concurrently conducted on Eocene, Pliocene and Quaternary sediment and a modern pollen rain study (ItzsteinDavey 2003;Atahan et al 2004;Itzstein-Davey 2004). This paper is the fourth in a series and will deal with the geochemical and palynological record of Two Mile Lake; and speci®cally focus on the representation of Proteaceae species/genera as a contribution to an understanding of the development of a Proteaceous rich¯ora in south-western Australia.…”