Red Gum Eucalyptus Camaldulensis Research Articles

Insect pest species of Eucalyptus in Gibraltar

Four invasive eucalypt-feeding insects, native to Australia, are recorded from Gibraltar for the first time: the gall-forming wasps Ophelimus maskelli (Ashmead) and Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae), the lerp-forming psyllid Glycaspis brimblecombei Moore (Hemiptera: Aphalaridae), and the bronze bug Thaumastocoris peregrinus Carpintero & Dellapé (Hemiptera: Thaumastocoridae), whilst the status of two Eucalyptus longhorned borers, Phoracantha recurva Newman and P. semipunctata (Fabricius) (Coleoptera: Cerambycidae), is summarised. The former five species have been found on the red-gum tree Eucalyptus camaldulensis Dehnh., growing in the urban environment in Gibraltar. The potential impact of these invasive species is discussed.

The red gum condition index: a multi-variable tree condition index for visually assessed river red gum (Eucalyptus camaldulensis) trees

ABSTRACTRiver red gum (Eucalyptus camaldulensis) is the dominant floodplain tree of the River Murray in south-eastern Australia. Drought and over-allocation of water have seen tree condition decline and environmental water is being used to aid recovery. An eight-variable visual assessment method is widely used to assess river red gum condition. These variables have been combined into a single aggregated index, the Red gum Condition Index (RCI), which comprises the Crown Condition sub-index (CCsi), which contributes 60% of the final score and assesses the amount of foliage in the tree crown; and the Secondary Variable sub-index (SVsi) which contributes 40% of the final score and aggregates measures of new tip growth, epicormic growth, reproduction, leaf die-off, mistletoe and bark condition. Relationships between variables define six condition categories. The R software package RCI calculates the RCI and provides quantitative and graphical outputs. Applied to two sites in South Australia, the RCI detected changes in tree condition attributable to environmental watering. As a responsive index with transparent categories the RCI can measure the current condition of river red gum stands and assess their watering needs. The RCI approach is readily transferrable to other tree species.

Sustaining recovery in red gum, black box and lignum in the Murray River Valley: clues from natural phenological cycles to guide environmental watering

ABSTRACTThe natural flow regime of the Murray River in south-eastern Australia has been fundamentally altered through regulation and extraction, with fewer, shorter floods, changing seasonality of flows and reduced floodplain connectivity. Ecosystems which evolved over millenia show serious stress and decline under the regulated regime. Environmental water allocations being returned to Murray Valley ecosystems to halt the decline and improve river health are not sufficient to re-create missing floods, but aim to mimic key elements of the natural water regime. For floodplain vegetation communities, the missing element is seasonal water availability to maintain condition of mature trees and trigger germination of seedlings. Dominant perennial vegetation species river red gum (Eucalyptus camaldulensis), black box (E. largiflorens) and lignum (Muehlenbeckia florulenta) suffered significant stress and death during the severe Millenium drought (2000–2010), but drought-breaking floods in 2010–2012 replenished soil moisture reserves. A new generation of seedlings germinated, and many environmental watering projects now focus on enhancing survival of these seedlings. Previous studies suggested that timing of phenological stages can indicate key timing for beneficial delivery of environmental water. These findings are being tested at Lower Murray Valley sites, to identify optimum timing for watering to support recovery in floodplain vegetation communities.

Can ecological thinning deliver conservation outcomes in high-density river red gum forests? Establishing an adaptive management experiment

Newly protected areas often have land-use legacies that affect their capacity to deliver conservation outcomes into the future. The management actions required to achieve conservation outcomes may be uncertain. This uncertainty may be resolved through experimental adaptive management that draws on knowledge of the ecology and history of the ecosystem. In New South Wales, Australia, river red gum (Eucalyptus camaldulensis) floodplain forests were gazetted as National Park in 2010, including Murray Valley National Park. Land-use legacies had resulted in one-third of river red gum forests and woodlands occurring as high-stem-density (>400 stems ha−1) stands at the time of gazettal. High-stem-density stands are characterised by dominance of narrow straight trees, a paucity of large and hollow-bearing trees, modified understorey vegetation and reduced coarse woody debris. A simple state-and-transition process model captured knowledge of the processes that led to the high-stem-density river red gum forest state being widespread. We describe the establishment of a manipulative experiment to evaluate whether ecological thinning can achieve conservation outcomes in high-stem-density stands of river red gum floodplain forest. The experiment was designed to reduce intrastand competition for water and other resources, and encourage development of spreading tree crowns. Future results will inform management decisions in high-stem-density stands of river red gum floodplain forests. The adaptive management approach employed provides a template for using knowledge of the ecosystem to resolve uncertainty about management, particularly in newly protected areas.

Evidence thatQuadrastichodella nova(Hymenoptera: Eulophidae) is the only Gall Inducer among Four Hymenopteran Species Associated with Seed Capsules ofEucalyptus camaldulensis(Myrtaceae) in South Africa

Three chalcidoid wasp species, Megastigmus zebrinus Grissell (Torymidae), Quadrastichodella nova Girault (Eulophidae) and Leprosa milga Kim & La Salle (Eulophidae), have each been described independently as gall inducers associated with Eucalyptus species (Myrtaceae). The finding that at times they emerge together from seed capsules of river red gum (Eucalyptus camaldulensis Dehnhardt) collected at the same site in South Africa, cast doubt on the accuracy of these earlier interpretations. The current study examined the gall inducing abilities of each of the three wasp species. During geographical surveys, all three species coexisted in seed capsules at 16 of the 61 sites sampled. A study of the seasonal emergence pattern of the three species, together with a fourth, locally abundant gall associate, Aprostocetus sp., showed that Q. nova and L. milga emerge during early summer, while the remaining two species emerge in smaller numbers throughout the year. Oviposition trials on sleeved branches of E. camaldulensis, from which all insects had previously been excluded, verified that Q. nova had the ability to induce galls, while both M. zebrinus and L. milga failed to do so. Only one type of gall of characteristic structure was encountered, which repudiates the possibility of a second gall inducer, and no indication of inquilinism was found. Megastigmus zebrinus, L. milga and Aprostocetus sp. are thus more likely to be parasitoids. DNA sequences were obtained for the adults of all four these species. By matching the DNA of identified adults with that of juvenile hymenopterans in the galls, it was confirmed that all four hymenopterans species developed within the seed-capsule galls of E. camaldulensis. Regrettably, this technique failed to give a clear indication of the exact host relationships between the various gall inhabitants. By dissecting seed capsules at different stages of gall development, the origin of the gall was proven to be in the placenta of one of the locules of a flower bud, and not in a seed or ovule, as previously reported.

Spatial Assessment of Water Use in an Environmentally Sensitive Wetland

Wetlands are among the most valuable ecosystems in the world and are crucial in supporting biodiversity. They also provide space for storing surface waters, where intense biological processing occurs that helps improve water quality. Human activities, particularly irrigated agriculture and urban developments instigating water diversions from rivers, have altered the hydrology of most wetlands. The Lower Murrumbidgee wetland, located in the Murrumbidgee River Catchment, is an example and is one of the significant wetlands across the Murray Darling Basin of Australia. Historic estimates show the volumes of water ranged from none in dry years to about 300 to 400 GL (1 GL = 10(9) L) in an average and wet year, respectively. The flows reaching the Lower Murrumbidgee wetland have been drastically reduced by at least 60% because of the upstream diversions introduced during the last century. These reductions have adversely affected the health of natural vegetation and agricultural crops in the Lower Murrumbidgee floodplain. This article presents the results of the quantification of total water consumption of various land uses in the Lower Murrumbidgee floodplain using the remote sensing-based Surface Energy Balance Algorithm for Land (SEBAL) modeling approach. The spatial analysis of actual evapotranspiration (ETa) shows that ETa rates are the highest (13-26%) for the red gum (Eucalyptus camaldulensis) forests both in summer and winter days. However, in terms of total ETa volume, lignum (Muehlenbeckia florulenta) constitutes the most significant part, which is around 14-30% of the total ETa volume for the area. Actual evapotranspiration from winter cereal cropping areas following the summer ponding is the third highest consumer of water after the river red gum and lignum. Actual evapotranspiration from the fallow land is also significant, representing 5-28% of total ETa from the region. In view of the extent of the unaccounted flows in the overall water balance of the system, there is a need to upgrade measuring and reporting infrastructure by strengthening the institutional and management arrangements to better gauge the efficiency of environmental and consumptive water use. The state-of-the-art technology of remote sensing-based SEBAL modeling proved to have potential for measuring actual water use with reliable accuracy and can be used for assessing the environmental and productive use of water from wetlands in other regions of Australia.

Amphibian communities associated with billabong habitats on the Murrumbidgee floodplain, Australia

Abstract A study of frog species richness and abundance at four permanent billabongs located in and around the city of Wagga Wagga, southern New South Wales, was carried out from the spring of 1991 to the autumn of 1992. During the sampling period a total of 404 individual adult frogs from six species were recorded. No egg masses or tadpoles were detected during a total of 32 survey hours. Four species of the Family Myobatrachidae represented 81% of the total number of adult individuals sampled, the remaining species belonging to the Family Hylidae. There were significant differences in the mean species richness and mean total number of adult individuals among billabongs. Significant positive correlations were recorded between total adult individuals, total frog species richness and the number of riparian plant species recorded at all billabongs. There were no significant correlations between adult frog numbers and meteorological and water quality parameters. The adults of the four most abundant frog species exhibited significant association with particular microhabitats surrounding billabongs; Crinia parinsignifera was associated with the creeping grass Paspalum distichum, Limnodynastes fletcheri with the rush Eleocharis sphacelata, L. tasmaniensis with sedges Cyperus spp. and the grass P. distichum and Litoria peronii with red gum Eucalyptus camaldulensis and introduced tree species. Differences in adult frog abundance between billabongs appears to be related to the disturbance of riparian vegetation by domestic stock, while the absence of eggs and tadpoles from these permanent billabongs may be explained by the presence of abundant exotic fish species in the billabongs.

Responses of clonal river red gum (Eucalyptus camaldulensis) to waterlogging by fresh and salt water

Summary. Effects of waterlogging by fresh and salt water on growth, water use, stomatal conductance and net gas exchange of 2 clones (M80 and M66) of river red gum (Eucalyptus camaldulensis Dehnh.) were studied under glasshouse conditions for 16 weeks over winter. Both clones tolerated extended periods of waterlogging with fresh water without effects on growth, stomatal conductance or net gas exchange. Formation of adventitious roots in the soil surface under waterlogging with fresh water was earlier in clone M80 than clone M66, as was recovery in water use. Thus, clone M80 may be more tolerant of soil saturation with fresh water than clone M66. In contrast, clone M66 may be more suited to saline conditions. Greater uptake of Na+ and Cl- occurred in clone M80. Lower water uptake of salt water and possibly greater tissue tolerance of salt by clone M66 may lead to greater survival under conditions where plants use saline groundwater. The results suggest that clone M80 would survive and utilise water when planted further upslope of highly salinised areas, with clone M66 better able to survive closer to such areas. The variation demonstrated between clones of E. camaldulensis indicates closer matching of their reclamation potential and the environmental conditions of damaged catchments should be possible.

Reliance of creek-side river red gums on creek water

Measurements of naturally occurring stable isotopes of hydrogen (2H) and oxygen (18O) were used to determine the importance of creek waters to river red gums (Eucalyptus camaldulensis Dehnh., Myrtaceae) on the banks of creeks in the semi-arid and saline Chowilla floodplain region of South Australia. The 2H and 18O concentrations of water sampled from trees were significantly different from those of the creek water, indicating that, generally, trees were not obtaining all their water from the creek. This was found even in trees overlying highly saline groundwater. Thus, saline groundwater and/or soil water were important water sources for the trees studied. The results indicated that the water relations of these trees are complex, and the trees may be less affected by changes in creek flow and/or salinity than was previously anticipated.

Clinotactic responses of Larval Silver Perch (Bidyanus bidyanus) and Golden Perch (Macquaria ambigua) to simulated environmental gradients

Larval silver perch (Bidyanus bidyanus) and golden perch (Macquaria ambigua) were subjected to gradients of light, depth, flow and wood leachate from river red gum (Eucalyptus camaldulensis) as well as a control treatment with no gradient. Both species were strongly attracted to light, while golden perch larvae were also attracted to river red gum and were carried downstream by water flow. Neither species displayed any response to depth. Gradient responses of silver perch were significantly more variable (P < 0.05) than those of golden perch, which may result in silver perch larvae being more widely distributed in floodplain habitats. Golden perch larvae may be more closely associated with inundated river red gum than silver perch larvae.

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.

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.

Rapid Effect of Drying on Development of Heart Cracks

SUMMARY Heart cracks developed in the end faces of small round specimens of red gum (Eucalyptus camaldulensis Dehn) independently of drying stresses and other factors such as the impact force of the tree striking the ground. It is concluded that the cracks were initiated principally as the result of relief of longitudinal growth stresses after crosscutting. When log ends were subjected to very mild drying conditions, heart cracks appeared after only 20 minutes exposure, apparently because of the additional stresses imposed due to shrinkage of the end surface or collapse.