EVIDENCE OF A HOLOCENE AND CONTINUING RECENT EXPANSION OF LOWLAND RAIN-FOREST IN HUMID, TROPICAL NORTH QUEENSLAND

The identification and radiocarbon dating of charcoal collected under tropical rain forest indicated that sclerophyll forests dominated by E ucalyptus occupied parts of the wet tropical lowlands in the Daintree region of North Queensland at least intermittently from 12,000 yr sp u ntil very recently. The results extend the late Pleistocene expansion of pyrophytic, sclerophyll forests which occur-red in the upland rain forests to a humid, megathermic coastal lowlands region. Unlike the ea rly Holocene re-expansion of rain forests which occurred generally on the uplands, the sclerophyll forests in the lowland study area were pr esent until at least 1400 yr sp. Changes in coastal geomorphology and coastline positions during the late Quaternary were examined in the st udy area by superimposing sea levels derived from published curves on sea-bed contours. The results indicate that a very rapid decrease in t he extent of the coastal plain occurred during the late Pleistocene. B etween 12,000 and 9000 yr sp, 26 km of the coastal plain was submerged and this would have inevitably resulted in concentrations of Aborigin al populations in the area of the present coastline. It is suggested t hat burning activities by Aborigines in the coastal lowlands were suff icient to reestablish sclerophyll forests during the latter part of th e Holocene from approximately 4000 yr sp following a warmer and wetter period which would have been conducive to rain forest re-expansion. A lthough the evidence suggests that the most recent rain forest recolon ization occurred in the study area more than 1000 years ago, the proce ss is still continuing elsewhere in the wet tropical lowlands in North Queensland. The process of eucalypt forest replacement by rain forest may have accelerated since the arrival of Europeans and the concomita nt decrease in Aboriginal management.