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Keywords:

  • Athrotaxis ;
  • carbon;
  • charcoal particles;
  • Eucalyptus ;
  • fire;
  • ITRAX ;
  • nitrogen;
  • Nothofagus ;
  • rain forest;
  • Southern Hemisphere

Abstract

Aim

To assess the long-term impacts of landscape fire on a mosaic of pyrophobic and pyrogenic woody montane vegetation.

Location

South-west Tasmania, Australia.

Methods

We undertook a high-resolution multiproxy palaeoecological analysis of sediments deposited in Lake Osborne (Hartz Mountains National Park, southern Tasmania), employing analyses of pollen, macroscopic and microscopic charcoal, organic and inorganic geochemistry and magnetic susceptibility.

Results

Sequential fires within the study catchment over the past 6500 years have resulted in the reduction of pyrophobic rain forest taxa and the establishment of pyrogenic Eucalyptus-dominated vegetation. The vegetation change was accompanied by soil erosion and nutrient losses. The rate of post-fire recovery of widespread rain forest taxa (Nothofagus cunninghamii and Eucryphia spp.) conforms to ecological models, as does the local extinction of fire-sensitive rain forest taxa (Nothofagus gunnii and Cupressaceae) following successive fires.

Main conclusions

The sedimentary analyses indicate that recurrent fires over several centuries caused a catchment-wide transition from pyrophobic rain forest to pyrophytic eucalypt-dominated vegetation. The fires within the lake catchment during the 6500-year long record appear to coincide with high-frequency El Niño events in the equatorial Pacific Ocean, signalling a potential threat to these highly endemic rain forests if El Niño intensity amplifies as predicted under future climate scenarios.