Calperum and Taylorville Stations plants and animals
More than 800 plants have been identified within Riverland Biosphere Reserve. Many of these species grow in semi-arid conditions and have special adaptations to withstand low erratic rainfall, harsh sunlight, salinity, low soil nutrient level and seasonal fires.
The plants have developed various techniques to reduce water loss, including reduced leaf surface area, leaves hanging vertical to decrease the impact of direct sunlight, while other plants orientate their leaf edges towards the sun. Leaf colours, such as blue-grey, reflect more sunlight and reduce the evaporation loss for the plant. Some species are perennial, waiting on seasonal conditions to germinate seed. Other species are reliant on fire to crack open and release seeds for germination.
The present fauna is only a remnant of what once existed before European settlement. Most fauna species that have declined were small ground dwelling animals, which depended on coarse grass, small shrubs for food and shelter. The loss of these habitats, the introduction of hard hoofed animals and rabbits, land clearing and salinity levels rising, have been major factors in declining animal numbers in the Mallee.
The mallee country has an extremely fragile soil structure, formed from wind blown particles deposited on a clay layer. The organic matter adds to an already thin nutrients layer of soil. The soil is held together by lichen crust and plant litter and shallow plant roots. Hard-hoofed animals and rabbits that crop plants close to the ground expose this layer to wind & water erosion.
The floodplains have been modified by locks and dams built along the Murray River. The river experiences dry periods, forming a string of pools to periods of varying flood levels enriched with nutrients and silt deposits. With the introduction of locks and dams there are smaller floods and the river and creeks flow all year round. The diversity of land and animal communities has been altered by the regulation of the river flow. There have been other changes, such as rising saline water table. Grazing and tree clearing have added to the modification of the landscape.
Significant monitoring programs track the physical and biological attributes of both properties. The ongoing, routine monitoring program included surveys of small vertebrates (mammals and reptiles), malleefowl and black-eared miner populations, floodplain grazing pressure, floodplain tree health, groundwater salinity, surface water quality and rainfall. Special purpose monitoring activities during the year included intensive rabbit monitoring in restoration areas, bush stone-curlew surveys and vegetation surveys.
Rainfall on both properties was close to the long-term average in 2009-10, leading to a generally strong response from vegetation in mallee and semi-arid woodland areas and from black box (Eucalyptus largiflorens) on the floodplain. The situation for river red gum (Eucalyptus camaldulensis) is less encouraging. While there has been increased vigour in stands of river red gums adjacent to wetlands that have received environmental watering there is a general, ongoing decline in the condition of river red gums in other areas.
Along with an increase in overall vigour of the mallee woodlands, there have been mixed trends in mallee bird populations. Encouraging levels of breeding activity were observed in black-eared miner colonies, including in areas that were impacted by the 2006 bushfires. Similar recovery has not been evident in some other mallee species such as the striated grasswren (Amytornis striatus). The annual small vertebrate (mammals and reptiles) surveys were conducted under unusually hot conditions, but still yielded above average catch levels as well as some unusual species observations. This supports the view that, overall, woodland biodiversity is on an improving trajectory.
Monitoring also revealed positive impacts of the filling of Lake Merreti and Lake Woolpolool. In November 2009 surveying around Lake Merreti recorded more than 3,000 waterbirds from 29 species. On Lake Woolpolool, which was watered after Lake Merreti, the numbers were lower, but this may have been at least partly due to widespread, major falls in other areas within the Murray-Darling Basin providing alternative habitat. Frog populations also responded well to the input of environmental water, the threatened southern bell frog (Litoria raniformis) being recorded in high numbers.