Timing and response of vegetation change to Milankovitch forcing in temperate Australia and New Zealand

Abstract

In this study a comparison is made of the late Quaternary palaeovegetation records of the last 20,000 radiocarbon years from temperate Australia and New Zealand. The present vegetation is generally different in composition and structure but the broad patterns of vegetation structure follow generally well-defined climatic gradients. The number of records is small and dating of some sequences is imprecise but they suggest that the timing of vegetation changes in southeastern Australia and New Zealand appear to be broadly the same until the Holocene. There are no reliable published records from southwestern Australia until the Holocene. During the Holocene, the climate changes are less pronounced and the records diverge. The degree of change within southwestern Australia may be spatially inconsistent while peak warming in New Zealand appears to develop and finish ahead of southeastern Australia. A late Holocene cooling appears to only be present for upland areas of southeastern Australia. There appears to be no clear relationship between changing vegetation patterns and insolation gradients except around the Pleistocene–Holocene boundary. This was when both Summer and Winter latitudinal insolation gradients were at a maximum for the last 20,000 radiocarbon years. This corresponds to the time when the Westerlies were assumed to be consistently strong all year. For other periods the Milankovitch signal is either weak or vegetation change is predominantly driven by other factors.