Preliminary Evidence for Pollen as an Indicator of Recent Floodplain Accumulation Rates and Vegetation Changes: The Barmah-Millewa Forest, SE Australia

Abstract

/ Preliminary analysis of pollen in three shallow sediment cores demonstrates that pollen is preserved in the seasonally dry, vertically accreting Barmah-Millewa Forest floodplain of the Murray River, SE Australia. Deposition characteristics of a floodplain are a critical component of catchment sediment budgets, but it has proven difficult to identify this important stratigraphic point in floodplains using radionuclide dating techniques. Pollen in a floodplain, as opposed to that preserved in lacustrine settings, provides opportunities for investigating the impact of European land-use on both sediment deposition and floodplain vegetation. Pollen from exotic plant taxa identified in floodplain sediments provided a chronostratigraphic marker for the boundary between pre- and post-European sediments in the Murray River floodplain. A maximum deposition rate of about 80 mm per 100 years is estimated from the sediment history. The pollen record shows vegetation changes within the forest since European settlement. These included changes in the density of the Eucalyptus forest; and in the composition of understorey herbs, sedges, and grasslands. Pollen concentration and charcoal and organic content also exhibit post-European changes. Thus, pollen analysis provides a technique for determining changes in sediment budgets and identifying major vegetation changes in floodplains.KEY WORDS: Pollen; Floodplain; Vegetation; Deposition; Budget; Sediment; Australia; Firehttp://link.springer-ny.com/link/service/journals/00267/bibs/24n3p359.html

Alterations in flood frequency increase exotic and native species richness of understorey vegetation in a temperate floodplain eucalypt forest

“…To date, soil cores from red gum forests have revealed changes following European settlement such as reduced fire, increases in soil organic matter content, increased densities of eucalypts and some shrubs, and reductions in sedges, rushes and chenopods (Kenyon and Rutherfurd 1999). Floodplain forests are subject to localised heterogeneity in both soil oxygen and nutrients, due to periodic saturation and development of anoxic conditions during the growing season (Neatrour et al 2007).…”

Long‐term effects of exclusion of grazing stock on degraded herbaceous plant communities in a riparian Eucalyptus camaldulensis forest in south‐eastern Australia

“…Vegetation structure and composition have been greatly altered since European settlement due to changes to flooding and fire regimes, stock grazing, weed invasion and timber harvesting (Chesterfield 1986;Bren 1992;Donovan 1997;Kenyon & Rutherfurd 1999). The negative impacts of stock grazing on riparian E. camaldulensis forests are well documented (Robertson 1997;Jansen & Robertson 2001; however, the potential for ecosystem recovery following the removal of grazing stock is poorly known.…”

River red gum and white cypress forests in south-western New South Wales, Australia: Ecological history and implications for conservation of grassy woodlands

“…Budda and hopbush are major woody weeds in box woodlands (Noble, 1997) and mistletoes have also been increasing since the 19th century (Forestry Commission of NSW, 1985;Reid and Yan, 2000;Jurskis, 2008). Soil cores from the red gum forests have corroborated many of the reported changes after European settlement, including reduced fire, increased soil organic matter, weed invasion, increased densities of eucalypts and some shrubs, and reductions in sedges, rushes and chenopods (Kenyon and Rutherfurd, 1999).…”