River Red Gum Forest Research Articles

DEFINING AND MANAGING ENVIRONMENTAL FLOWS: INPUTS FROM SOCIETY

Two key questions regarding the management of Australia's riverine environments are addressed: how much water should be allocated for environmental flows; and how should water entitlements for environmental flows be acquired and managed. First, an application of the choice modelling technique in the context of River Red Gum forests along the River Murray is used to demonstrate how the marginal values of water for the environment can be estimated for comparison against prices paid by extractive users of water. Second, mechanisms in the public and private sectors for the purchase of environmental water are contrasted.

Responses of a Carnivorous Marsupial (Antechinus flavipes) to Local Habitat Factors in Two Forest Types

Abstract Ecosystems around the world have been degraded or destroyed by human activities, including regulation of river flows, clearance of vegetation, and removal of fallen timber. In southeastern Australia much of the original vegetation was converted to farmland. Remaining forests such as hilly box–ironbark and floodplain river red gum (Eucalyptus camaldulensis) are mostly regrowth. The yellow-footed antechinus (Antechinus flavipes) inhabits both types of forests and is the only small, native, carnivorous mammal on most floodplains in southeastern Australia. In this region, frequency of flooding has been reduced by regulation of river flows, which has led to decline in conditions favorable for flood-adapted terrestrial and aquatic organisms. Here, we compared numbers of A. flavipes in box–ironbark forests, and in river red gum forests that were deprived of floods; partially inundated with environmental flows; flooded naturally; and watered in large, artificial floods. We found that abundance of A. flav...

Current Loads of Coarse Woody Debris on Southeastern Australian Floodplains: Evaluation of Change and Implications for Restoration

AbstractWe evaluated the status of coarse woody debris (CWD, fallen wood) on floodplains of the southern Murray‐Darling basin of southeastern Australia. The floodplains are dominated floristically by the river red gum Eucalyptus camaldulensis. Aerial survey techniques were used to estimate the amounts of woody debris within 200 m of the channels along 2,442 km of 11 rivers of the system, including the Murray and Darling Rivers and the Darling Anabranch. Aerially based indices were converted into wood volumes by using ground‐truthing at a selection of sites; there was a strong correlation between index values and measured wood volume densities. For thickly forested sites such as Barmah, Gunbower Island, and the Ovens floodplains, the aerial method was not useful, so ground measurements at randomly positioned sites within the forests were used. Volumes were translated into mass by using conversion factors drawn from the literature. We estimated that total tonnage on approximately 221,000 ha of floodplain forests was 4.175 ± 0.579 × 106 tonne. In the larger forested blocks (>7,000 ha), mean wood densities ranged between approximately 12 tonne/ha on the lower Goulburn up to approximately 24 tonne/ha at Barmah State Forest. The area‐weighted mean for the entire area was approximately 19 tonne/ha. A main purpose of the research was to place these figures into an historical perspective to evaluate implications for restoration. A thorough search of historical documentation revealed that there are no extant data upon which to estimate pre‐European settlement levels. We used information from an apparently undisturbed “unmanaged” site in the Millewa forests of southern New South Wales as a basis. Wood density there corresponded to a mean figure of 125 tonne/ha wood‐mass density. By using this figure we estimate that CWD levels on the southern Murray‐Darling basin may be of the order of 15% of pre‐European settlement levels. Full restoration of the 221,000 ha surveyed would require 23.5 ± 0.579 × 106 tonne, which is equivalent to about 600,000 mature (1 m diameter at breast height) river red gum trees or the amount of timber derived from clear felling about 115,000 ha of river red gum forest at current stocking levels. We discuss the implications of this massive deficit and possible short‐ and long‐term solutions.

Barmah-Millewa forest environmental water allocation

The formal allocation of water for the environment is a developing area of river management both scientifically and in terms of community participation. This case study, illustrating the recent use of the Barmah-Millewa Forest Environmental Water Allocation (EWA), provides a practical demonstration of community participation in environmental water management, the application of hydrological and biological "triggers" and a positive, demonstrable biological outcome from an environmental water allocation. The Barmah-Millewa Forest covers an area of 70,000 ha across the floodplain of the Murray River, upstream of the town of Echuca. About half the forest is in NSW (Millewa) and half is in Victoria (Barmah). The Barmah Forest is a Wetland of International Importance listed under the Convention on Wetlands - Ramsar Convention. The forest is the largest river redgum forest in the world. The natural flooding cycle associated with the forest has been significantly altered by regulation of the Murray River--impacting upon the overall health of the forest ecosystem. Recognising this, the Murray Darling Basin Commission developed a water management strategy for the forest to enhance forest, fish and wildlife values. To implement this strategy, between 1990 and 1993 reports were completed and community consultation took place. In 1993 the Murray Darling Basin Ministerial Council approved allocation of 100 Gigalitres of water per year, provided in equal shares by NSW and Victoria, to meet the needs of the forest ecosystem and in 1994 the Barmah-Millewa Forum was established under the Murray-Darling Basin Agreement. The vision for the Forum is to maintain and, where possible, improve the ecological and productive sustainability of the Barmah-Millewa Forest and to establish a planning and operational framework to better meet the flooding and drying requirements of the riparian forests and wetlands. Between October 2000 and January 2001 the Barmah-Millewa Forest Environmental Water Allocation was used for the second time. A total of 341 GL was released as an EWA. This amount represented only 8% of the total flows downstream of Yarrawonga Weir from September 2000 and January 2001. The strategic use of the relatively small amount of water enabled flooding to be maintained and ensured significant breeding success for water birds and other biota in the Forest.

Influence of remnant and landscape attributes on Australian woodland bird communities

This study investigated relationships between the composition of bird communities and remnant and landscape attributes including area, shape, vegetation type and position in the landscape. Vegetation type was the strongest determinant of bird communities. The bird community of river red gum forests was most different from that of white cypress pine woodlands, with the bird communities of other vegetation types intermediate between these two extremes. Honeyeaters and hollow-nesting birds were associated with river red gum forests, whereas small insectivores were associated with white cypress pine woodlands. Bird communities also varied significantly with remnant size. Small insectivores were more likely to be found in remnants larger than 200 ha, whereas noisy miners and grey butcherbirds were more likely to be found in remnants smaller than 100 ha. Vegetation type, remnant area, absence of noisy miners and presence of small insectivores are interrelated. It is likely that the aggressive noisy miner, rather than remnant size per se, determines the presence or absence of small insectivores in remnants. Remnant attributes appeared to be more important than landscape attributes in determining the composition of bird communities, although the widespread occurrence of noisy miners may inhibit the benefits that landscape vegetation might provide. As long as an aggressive edge specialist dominates small remnants and there is a shortage of quality, core patches that might benefit from connectivity, we consider that a focus on landscape connections is a dangerous diversion for efforts directed towards biodiversity conservation. Large, high-quality patches must be established and protected for the conservation of declining birds.

The effect of flooding and flood timing on leaf litter breakdown rates and nutrient dynamics in a river red gum (Eucalyptus camaldulensis) forest

AbstractComparisons of litter standing‐stocks in low‐lying and higher areas of the floodplain and the effects of controlled flooding events on leaf litter decomposition and leaf litter nutrients were examined during autumn and winter in a southeastern Australian river red gum (Eucalyptus camaldulensis) floodplain forest. The mean mass of total litter and some litter components was significantly greater in autumn than in winter but there were few differences in litter mass between low‐lying flood runners and higher sites (1.5 m) on the floodplain, regardless of season. Leaf decomposition was more rapid in flooded areas than in non‐flooded areas and was significantly faster in autumn than in winter. In flooded leaves, concentrations of phosphorus and nitrogen dropped rapidly during the first 3 days of each experiment, increased to near original after 7–10 weeks and then decreased again. After 112 days of decomposition the C:N:P ratios of leaf litter increased, but this effect was most marked for flooded leaves. Simple models of leaf litter dynamics indicated that leaf litter standing‐stocks in low‐lying flood runners would be reduced by flooding, particularly during autumn. In contrast, models predicted a net gain in standing‐stocks of leaf litter to be higher on the floodplain, particularly in autumn. Alteration to the seasonal timing of floods by river regulation has probably decreased litter standing‐stocks and nutrients available in low‐lying areas of the floodplain to support the production of macrophytes and biofilms during winter and spring floods.

Development of silviculture in the native State forests of Victoria

Summary An historical perspective of silviculture in the native State forests of Victoria is presented covering the impacts of European settlement, initiation of active management, the application of methods based on sound ecological principles and, since the 1970s, a stronger focus on social and environmental objectives. The development of silviculture in the major forest types is discussed, including: ash, Low Elevation Mixed Species, High Elevation Mixed Species, Box-Ironbark and river red gum forests. Organisational arrangements for implementation of silviculture are described, along with processes for development of new and improved systems. The ongoing trend to improve on-ground delivery of silviculture through the use of new technology and the development of performance monitoring and improvement systems for sustainable forest management is also discussed.

Diet and Habitat of Emus Dromaius novaehollandiae in the Grampians Ranges, South-western Victoria

SummaryThe diet of the Emu Dromaius novaehollandiae was studied by analysis of droppings at four sites in Victoria Valley, Grampians National Park, south-west Victoria, from March to July, 1984. Little variation occurred in diet between the study sites. Emus concentrated on particular plants; dicotyledons comprised 88–95% of droppings by dry weight in each monthly sample, with Epacridaceae, mostly flowers of the Flame Heath Astroloma conostephioides, the most abundant, especially after March. Monocotyledons were unimportant, although aquatic Streaked Arrowgrass Triglochin striata was recorded February—April at the swamp site. Other plant species and non-food items constituted only a small part of the diet. Emus used a swampy site in warm, drier months, but left as temperatures decreased, and when rains arrived in July. Riparian forest—River Red Gum forest was also frequented during warmer periods while open River Red Gum forest and heath/heathy woodland became more important in colder months. Habitat usage appeared to relate to availability of food and water, and to a lesser extent, shelter.

Leaf dynamics and insect herbivory in a Eucalyptus camaldulensis forest under moisture stress

Abstract The influence of soil moisture content on leaf dynamics and insect herbivory was examined between September 1991 and March 1992 in a river red gum (Eucalyptus camaldulensis) forest in southern central New South Wales. Long‐term observations of leaves were made in trees standing either within intermittently flooded waterways or at an average of 37. 5m from the edge of the waterways. The mean soil moisture content was significantly (P≤0.05) greater in the waterways than in the non‐flooded areas. Trees in the higher soil moisture regime produced significantly larger basal area increments and increased canopy leaf area. This increase in canopy leaf area was achieved, in part, through a significant increase in leaf longevity and mean leaf size. Although a greater number of leaves was initiated and abscissed per shoot from the non‐flooded trees, more leaves were collected from litter traps beneath the denser canopies of the flooded trees. Consumption of foliage by insects on the trees subjected to flooding compared to the non‐flooded trees was not significantly different. However, the relative impact of insect herbivory was significantly greater on the non‐flooded trees. Leaf chewing was the most common form of damage by insects, particularly Chryso‐melidae and Curculionidae. No species was present in outbreak during this study. Leaf survival decreased as the per cent area eaten per leaf increased. In addition, irrespective of the level of herbivory, leaf abscission tended to be higher in E. camaldulensis under moisture deficit. The influence of soil moisture content on the balance between river red gum growth and insect herbivory is discussed.

Insect Herbivory in a River Red Gum (Eucalyptus camaldulensis Dehnh.) Forest in Southern New South Wales

ABSTRACTThe influence of insect herbivory on tree growth was examined in a river red gum (Eucalyptus camaldulensis) forest in southern New South Wales. Mature E. camaldulensis trees treated with the systemic insecticide monocrotophos lost an average of 13.9%± 1.6 of potential leaf area from current season's foliage compared with 22.3%± 1.6 from untreated trees. the most common form of damage was caused by leaf‐chewing insects. Leaf tissue lost by sap‐sucking, leafmining or galling insects was minimal. A total of 49 species of phytophagous insects were collected from the E. camaldulensis canopies. the insecticide‐treated trees had significantly higher rate of diameter increment (2.9 cm ± 1.1 vs. 0.7 cm ± 0.1). They also possessed healthier crowns and significantly larger leaf length/width ratios. the insecticide treatment had no significant effect on potential area per leaf or mean specific mass of the sampled foliage. the level of insect herbivory in nearby saplings was not significantly different to that of the mature trees.

Effects of river red gum, Eucalyptus camaldulensis, litter on golden perch, Macquaria ambigua

Aquaria with added river red gum, Eucalyptus camaldulensis, litter became hypoxic, with decreased pH and contained up to 30 mg 1−1 tannin and lignin. Survival of golden perch, Macquaria ambigua, larvae in aquaria treated with a simulated annual litter density of 450 g m−2 for 72 h was 14·9% for 15‐day‐old larvae and 0% for 8‐day‐old larvae. A litter density of 1223 g m−2 resulted in total mortality for both age groups of larvae. Aeration increased survival of larvae to a minimum of 68·8% in 1223 g m−2 litter treatments compared to 89·8% in aerated controls and 86·8% in non‐aerated controls. A kinetic behavioural assay was used to detect alarm responses in golden perch larvae and juveniles exposed to leachates from river red gum bark, leaves and wood. Eight‐day‐old larvae exposed to bark and wood leachates (0·001–10 g 1−1) exhibited an initial period of hyperactivity, followed by a concentration‐dependent decrease in spontaneous activity. Larvae exposed to leaf leachates displayed only a decrease in spontaneous activity. Four‐month‐old juveniles exposed to wood leachates were also initially hyperactive, then progressively developed mild hypoactivity at increasing leachate concentrations. Juveniles exposed to wood leachates at 20g 1−1 for 30min suffered 97·5% mortality in 96 h. Wood leachates induced dose‐dependent lamellar fusion, epithelial dissociation and necrosis in the gills. The presence of toxic leachates and low oxygen availability in flooded river red gum forests may make these habitats unsuitable as nursery areas for native fish.

Modelling the influence of River Murray management on the Barmah river red gum forests

Summary Three modelled sequences of estimated average monthly flows of the River Murray were used to study the likely effects of river management on the frequency and duration of flooding of the river red gum forests at Barmah in northern Victoria. One model gave monthly flows in the River Murray at Yarrawonga from 1890 to the present with no regulation or diversions. The second model gave flows with Hume Dam regulation and diversion. The third model gave flow with Dartmouth and Hume Dam regulation and diversion. This corresponds to “current” regulation. The Hume Dam (only) sequence was regarded as the one that corresponded best to the state of the river for which forest flooding data were available. A relation between the average monthly flow (expressed in gigalitres per day) and the percentage of forest flooded was used to transform the historical sequences of monthly flows into the corresponding maximum monthly percentages of forest flooded. This, in turn, was used as input in a grid cell model of the forest flooding based on historical flood maps. From the estimates of the maximum monthly extent of flooding between 1890 and 1984, statistical parameters describing the change in flooding regime for the “natural” and the “current” river were computed. The results showed an average annual reduction of 1–2 months duration in flooding and a substantial increase in the time between flooding for all sites. Many sites may suffer a 50% reduction in flooding frequency. This suggests that the vigor of the red gum within the Barmah Forest will be diminished, and some red gum areas may revert to dryland box forest.

The contribution of River Murray tributaries to the flooding of Barmah forest

Summary The contribution of River Murray tributaries to the flooding of the Barmah river red gum forest was examined. The main stem of the River Murray above Lake Hume was the major source. Removal of this would lead to a 55% decrease in forest flooding. Removal of either the Ovens or the Mitta Mitta Rivers would give a 30% reduction in flooding. Removal of the Kiewa River would give a 15% reduction in flooding. All tributaries act to some extent in concert. A backwater influence due to high water levels at the downstream confluence of the Goulburn and Murray Rivers may cause high water levels at Barmah. Because of the short-lived nature of these high water levels it is unlikely that such floods penetrate far into the forest.

The contribution of river murray tributaries to the flooding of barman forest

The Barmah River Red Gum forest are part of a larger tract of such forests along the River Murray. It is known that river flooding provides an important source of water for the sustenance of these forests. The contribution of River Murray tributaries to the flooding of these forest was examined. The main stem of the River Murray above lake Hume was the single most important source. Removal of this would lead to a 55 percent decrease in forest flooding. Removal of either the Ovens or the Mitta Mitta would lead to a 30 percent reduction in flooding, while removal of the Kiewa river would lead to a 15 percent reduction in flooding. No particular tributary can be regarded as a source of extreme forest floods since all tributaries more or less act in concert. A backwater influence of high water levels at the down strewn confluence of the Goulburn and Murray Rivers leads to high water levels in the River at Barmah. However, because of the short-lived nature of such high, water levels it is unlikely that such floods penetrate very far into the forest unless they are also associated with flows in the River Murray.

Use of map analysis to elucidate flooding in an Australian Riparian River Red Gum Forest

Red gum (Eucalyptus camaldulensis) forests occur on extensive floodplains along the river Murray in Australia. This type of forest is unusual because of its high quality in a semiarid area, the absence of woody species other than red gum, and its survival on a deep, intractable, swelling clay soil of depths exceeding 20 m. This soil probably acts as an aquiclude. The forests require flooding to thrive and regenerate. For many years there has been speculation that irrigation regulation of the river was reducing forest flooding. A grid cell analysis of flood maps of areas flooded over a period of 22 years showed that vegetation communities and forest site quality were statistically related to the flood frequencies of sites. The percentage of forest inundated was dependent on the peak daily flow during the period of inundation. A historical analysis of the estimated percentage of forest inundated showed a substantial influence of river regulation on both timing and extent of inundation. Estimates of historical floodings showed that the environment is one that changes rapidly from wetland to dry land. Although not without limitations, the analysis produced information not available from other sources.

River regulation and associated forest management problems in the River Murray red gum forests

Summary The Barmah and Millewa Forests contain extensive areas of Eucalyptus camaldulensis (river red gum) forest growing on a flood plain of the River Murray. In the past, under natural conditions, the forests were extensively flooded in winter/spring of most years, often for two or more months' duration. Indeed, the best quality forest has developed on those areas most regularly flooded. However, following construction of Lake Hume the river flow has been regulated since 1934 with the effect of reducing winter/spring flows and increasing summer/autumn flows for irrigation purposes. As a consequence, the frequency and duration of winter/spring flooding of the forest has decreased and also localised and prolonged flooding of the forest in summer/autumn has led to deterioration and death of some stands. With completion of Lake Dartmouth on a major tributary, the Mitta Mitta River, the effects of river regulation will be accentuated. A summary of river flow data from 1886 to 1984 is presented, showing natur...

Changes in the vegetation of the river red gum forest at Barmah, Victoria

Summary Changes in the vegetation of Barmah State Forest, situated on the floodplain of the River Murray in northern Victoria and dominated by river red gum (Eucalyptus camaldulensis), have been deduced by examination of historical and recent evidence. The factors influencing vegetation changes have been (1) a reduction in frequency of burning following the displacement of aboriginal tribes from the area, (2) intense grazing by rabbits from the 1880s until their control by myxomatosis, (3) grazing by domestic stock, and (4) the effect of river regulation including less frequent winter/spring flooding and the entry of water into the forest during summer as a result of high river levels managed for crop irrigation purposes. In addition to the described effects on the health of trees, the area of grassland has been reduced significantly. Extensive areas previously dominated by Moira grass, common reed and/or cumbungi are now covered with red gum forest or beds of giant rush.