Total Catchment Management and the return of eco-systems to "a natural state" strategies are the current concern of environmental managers. To meet these objectives environmental data at spatial and temporal scales relevant to the landscape are necessary. The Murray River floodplain has a long history of Aboriginal habitation, but only inferred environmental information. European settlement of the region began in the early 1800s when. Settlement was rapid with early reports of the country from explorers and settlers being biased, by necessity, toward the suitability of land for grazing or agriculture. The result is that early historical environmental records are short and incomplete. The aim of this project is to provide extended environmental data on the dynamics of the Barmah Forest floodplain during the late-Holocene and European periods using stratigraphic and palaeoecological data to identify sediment, fire frequency and vegetation responses to European land-use practices.

The Barmah forest is the largest Eucalyptus camaldulensis (Denh.) (River Red Gum) forest in southern Australia. It is the Victorian section of the Barmah-Millewa Forest that lies between Tocumwal, Deniliquin and Echuca and occupies a flood-prone, low-lying region of 28,900 ha adjacent to the Murray River. Sediments consist of vertically accreting, seasonally dry silts and clays. Edward Curr first used the forest for grazing sheep in 1842. Cattle grazing and logging followed with gold-mining in upper catchment streams a major activity during the 1860s. Completion of the Hume Dam in 1937 and intensive regulation of Murray River flow for irrigation downstream of the forest has resulted in high summer flows replacing the natural high winter/spring flows. Summer floods within the forest are now common.

Sediment cores were extracted from six sites within the forest to identify historical spatial patterns within the forest. These cores have been sampled to give the fine temporal resolution necessary for determining short-term landscape evolution. To date the cores have been analysed for sediment particle size and magnetic susceptibility (6 cores); charcoal (3 cores); organic content (2 cores); and pollen (2 cores). AMS radiocarbon dates have been obtained for all cores and OSL dates are pending for 2 cores. In addition results are available from an earlier preliminary study. Pollen results are presented as concentrations rather than relative percentages of the dryland pollen sum as this gives a better indication of each species response to changes in landscape conditions in this semi-arid environment.

The pre-Historic Murray River floodplain was a relatively stable landscape. There is little variability in sediment composition, water content and loss on ignition values. The charcoal record shows fire to be an integral part of the landscape. However, the pollen record at Hut Lakeand the Millewa site indicate variability over time in Eucalyptus, Cupressaceae, Allocasuarina and wetland taxa. The Poaceae record indicates Hut Lake has always been a grass plain.

For the Historical period sediment analyses show there is now greater variability over time with recent, major changes in sediment composition and increased deposition rates. Each site has responded independently to changes during this time. Micro-charcoal data and CP:pollen sum ratios suggest that regional fire frequency has increased although charcoal particles in the record have decreased (this may be due to the increase in sediment deposition rates). The macro-charcoal records show that at Hut Lake fire frequency within the forest has remained unchanged, while at Gower’s Gate the near-by charcoal burning activities are evident in the record.

The presence of Pinus pollen was used to determine the stratigraphic cultural boundary. The pollen record shows major changes at Hut Lake, Gower’s Gate and the Millewa site. Comparisons between the pollen and sediment records show Eucalyptus regeneration after major flood events at the first two sites. At all sites Eucalyptus density increases. This increase verifies historical accounts of a more open forest at the time of European settlement. The loss of Cupressaceae at the Millewa site may be due to early European preference for this wood, whereas the increase at Hut Lake may represent a Cupressaceae plantation nearby. At Gower’s Gate the MDS analysis shows a gradual change in vegetation over time. Wetland taxa indicate hydrological changes consistent with river regulation and increased flooding in the forest.

Grazing pressure, combined with hydrological changes has resulted in an increase in the unpalatable Carex appressa in the forest understorey. Completion of the Hume Dam and management of Murray River flows primarily for summer irrigation have resulted in increased Eucalyptus camaldulensis germination success and progressive loss of the Moira grass plains due to Eucalyptus camaldulensis. Changes to catchment land-use have caused changes in sediment composition and deposition rates.