The late Quaternary vegetation history of the south‐central highlands of Victoria, Australia. II. Sites below 900 m

Abstract

The late Quaternary vegetation communities of the south‐central highlands of Victoria are constructed from analyses of pollen and charcoal, and macroscopic plant remains preserved in Sphagnum bogs. The sites, located in eucalypt forest or woodland, form an altitudinal sequence with the component Eucalyptus species varying with altitude and with small pockets of Nothofagus cunninghamii (Hook.) Oerst. in close proximity to the higher sites. The record from the sites above 900 m covers the last 32 000 years, and the record from the lower sites extends from at least 12 000 BP. Around 32 000 BP the region was predominantly covered by a mosaic of alpine feldmark and herbfield, with small patches of Eucalyptus and Nothofagus woodland close to sea level when summer temperatures were probably 5°C lower than present. Lowest values, probably 7°–8°C below present, occurred between 19 800 and 16 900 BP, when alpine communities were most widespread and much of the Central Highlands was treeless. Around 12 000 BP alpine taxa disappeared or were greatly reduced, first at the lower sites. There was an associated rise in the treeline with the movement upslope of Nothofagus and eucalypt forest as a result of a general increase in temperature and probably effective precipitation. By 6000 BP wet eucalypt forest and Nothofagus reached their maximum postglacial extent at all sites, possibly related to a further increase in temperature, at least 2°C lower than present, and higher effective precipitation. A continuing increase in temperature, or an increase in continentality, and a decrease in effective precipitation led to increased fire hazard and retraction of rainforest and wet sclerophyll or tall open forest toward present‐day values. Nothofagus disappeared from the sites below 900 m. The activities of humans pose further threats to remaining forest communities. The record of vegetation and environmental change derived from the local and regional picture from eight sites reinforces and complements that from the individual sites. For example, combining the records overcomes to some extent taphonomic problems such as the effect of streams that flow close to all sites, and other limitations including problems of dating, poor preservation and variable sedimentation rates.

Altered Ecologies: Fire, climate and human influence on terrestrial landscapes: Terra Australis 32

“…Nothofagus was more common near the treeline in the late Pleistocene in New Guinea, in cooler (although possibly cloudier and so less exposed to frost) conditions (Walker and Hope 1982;Hope 2009). The particularly high frost resistance recorded in N. cunninghamii may reflect substantial increases in frost resistance that evolved during glacial periods, particularly if refugia were colder and drier than is currently experienced (McKenzie 1995(McKenzie , 2002Worth et al 2009), and might involve more complex genetic change. However, frost resistance is the Figure 3.…”

“…Even more remarkably, the regional palaeoenvironmental record does not contain a strong signature of prehistoric human activity. For example, Geoffrey Hope's extensive palynological and sedimentological studies of mountain mires in New South Wales and the ACT found no obvious signature of prehistoric burning that might be linked to human activity , a result that is replicated elsewhere in the region (Ladd 1979;Kershaw and Strickland 1989;Dodson et al 1994;McKenzie 1997McKenzie , 2002Mooney et al 1997). In contrast, many sites show a marked increase in charcoal associated with the appearance of Pinus pollen, marking the onset of European land management practices .…”

Holocene vegetation change at treeline, Cropp Valley, Southern Alps, New Zealand

“…It is possible that drier conditions earlier in the Holocene may have delayed this maximum. In south-central Victoria, forest reached current levels at several high-altitude sites after 11,500 cal BP (McKenzie 1997(McKenzie , 2002Kershaw et al 2007), but wet Eucalpytus forests and Nothofagus did not achieve maximum extent until ca. 7000 cal BP (McKenzie 2002).…”

“…In contrast, Tasmania and southeastern Australia, in part because of Peter Kershaw's long-standing interest, have many intensively investigated subalpine to alpine sites and a wealth of information on their treeline history (e.g. Kershaw and Strickland 1988;McKenzie 1997McKenzie , 2002Kershaw et al 2007).…”

Fire on the mountain: A multi-scale, multi-proxy assessment of the resilience of cool temperate rainforest to fire in Victoria’s Central Highlands

“…This has been achieved through the development and analysis of multiple pollen-based reconstructions, which have shown several common, and consistent, patterns. McKenzie (1997McKenzie ( , 2002 of several high-elevation (>900 m) sediment cores that have been dated to ca. 31,500 BP and again from 20,000 BP, at which point the N. cunninghamii pollen are found continuously until the present, albeit with fluctuating abundance.…”