Dynamics of temperate rainforest from fine resolution pollen analysis, Upper Ringarooma River, northeastern Tasmania

The relationship between sclerophyll forest and temperate rainforest in Tasmania is believed to be driven by climate, soils and fire regime; however, this has been tested infrequently on time frames relevant to the longevity of the major forest trees involved. This study uses sediments in four small hollows from within a rainforest stand in the Upper Ringarooma valley in northeastern Tasmania, Australia, to analyse vegetation dynamics and disturbance over the last 1000 years. Pollen-vegetation relationships were investigated by comparing pollen rain and current vegetation, and the chronology was established by radiocarbon and lead-210 dates. The lead-210 data indicate that the two Sphagnum humus profiles were not always closed systems for inorganic inwash; however, the pollen and charcoal records are generally consistent indicating that a mixed Eucalyptus-Nothofagus forest shifted to a Nothofagus dominated rainforest as fire became a less prominent component of the environment. About 400 years ago Leptospermum lanigerum invaded the community as canopy gaps developed, possibly as the older Nothofagus cunninghamii trees died. There is no strong evidence of invasion by Atherosperma moschatum as suggested by some models of forest dynamics in these forests in Tasmania. In this stand of forest, fire and erosion following flooding have been the major causes of disturbance.