The influence of climatic change, fire and species invasion on a Tasmanian temperate rainforest system over the past 18,000 years

We aim to understand how did cool temperate rainforest respond to changes in climate and fire activity over the past 18 kcal yrs, interrogating the role that flammable plant species (such as Eucalyptus) have in the long-term dynamics of rainforest vegetation. We used high-resolution pollen and charcoal analysis, radiometric dating (lead and carbon), modern pollen-vegetation relationships, detrended correspondence analysis, rarefaction (palynological richness), rate of change and granger causality to understand the patterns and drivers of change in cool temperate rainforest from the sediments of Lake Vera, southwest Tasmania through time. We record clear changes in key rainforest taxa in response to climatic change throughout the record. The spread of rainforest through the lake catchment in the early and mid- Holocene effectively negated disturbance from fire despite a region-wide peak in fire activity. An anomalously dry period in the late-Holocene resulted in a local fire that facilitated the establishment of Eucalyptus within the local catchment. Granger causality tests reveal a significant lead of Eucalyptus over fire activity in the Holocene, indicating that fires were enhanced by this pyrogenic taxon following establishment

Late-glacial and Holocene records of fire and vegetation from Cradle Mountain National Park, Tasmania, Australia

Fire activity was reconstructed at five sites and vegetation history at three sites in northwest Tasmania, Australia in order to examine the climate and human drivers of environmental change in the region. Watershed-scale reconstructions of fire were compared to regional vegetation history. Fire activity was very low until ca. 12,000 cal yr BP. An early-Holocene fire maximum, ca. 11,800–9800 cal yr BP, occurred during the warmest interval of the Holocene as recorded by regional paleoclimate proxy records. This period of elevated burning was also coincident with an increase in arboreal sclerophyll plant taxa. A maximum in rainforest taxa occurred at ca. 8500-5800 cal yr BP concurrent with sharply diminished biomass burning compared with the early Holocene. The increase in rainforest taxa is attributed to elevated effective moisture during this period. Conditions were drier and variable in the late Holocene as compared with earlier periods. A rise in fire activity at ca. 4800-3200 cal yr BP was accompanied by an increase in sclerophyll taxa and decline of rainforest and subalpine taxa. Elevated palynological richness during the late Holocene co-occurred with high levels of charcoal suggesting that fires promoted high floristic diversity. At Cradle Mountain, there is no clear evidence that fire regimes or vegetation were extensively modified by humans prior to European settlement. Climate was the primary driver of fire activity over millennial timescales as explained by the close relationship between charcoal and climate proxy data.This research was supported by National Science Foundation grant OISE-09664472 to C. Whitlock and Australian Research Council grants DP0664898 to S. Haberle DP110101950 to D.M.J.S. Bowman