Eastern Darling Research Articles

Paleoecology of the Plio-Pleistocene of Queensland: Ecological Shifts Evidenced From Fauna at the Darling Downs

The continent of Australia is currently warming approximately thirty-five percent faster than the rest of the globe, with the warmest year on record coinciding with the most extreme bush fires. While effects of ongoing climate change are apparent over the past century, Australia has experienced pronounced aridification since the Miocene/Pliocene, transitioning from tropical forests to more open habitats. To better contextualize on-going climate change, we assess the ecology and paleobiology of mammalian faunas in Australia from the Pliocene to the Present in the Darling Downs region of Queensland Australia. Via the analysis of stable isotopes from tooth enamel and dental microwear texture analysis of the chewing surfaces of teeth, we clarify the ecology and paleobiology of medium to large marsupials from the Pliocene Chinchilla Sands and Pleistocene Eastern Darling Downs faunas. By comparing these ancient marsupial mammal communities to extant marsupial mammals that inhabit these regions today, we further demonstrate that the most dramatic changes between past ecosystems are clearly between those of the Present and the Plio-Pleistocene—indicated that the Darling Downs region of today is disparate as compared to the past. Most notably, Macropus giganteus consumes vegetation that is ~5.6‰ higher in δ13C values today than during the past, indicating feeding in a significantly more open landscape. The Pliocene and Pleistocene of the Darling Downs are instead dominated by mixed-feeding and browsing taxa, with several taxa exhibiting diets disparate from modern analogues (e.g., an abundance of C4 browsers). Collectively, these deep-time temporal comparisons are a clear example of how ecological communities observed today do not represent the full range of ecological niches occupied in the past and highlight the dramatic climate-departures experienced today.

Restoration potential of Brigalow regrowth: Insights from a cross‐sectional study in southern Queensland

The study was undertaken at Bulli State Forest, in the eastern Darling Downs, Queensland, Australia. The State Forest includes a minor area (65 ha) of sedentary cracking clay in the western portion with limited gilgai development. This area supports remnant (undisturbed) open forest of Brigalow and Belah (Casuarina cristata Miq.) (Regional Ecosystem 11.9.5, Young et al. 1999) and adjacent regrowth Brigalow communities of two ages (39 and 27 years old). Clearing permits indicate that the 39-year old regrowth (herein referred to as ‘old regrowth’) was originally cleared by ringbarking in 1968 and has been allowed to regenerate without subsequent clearing or thinning. The 27-year-old regrowth (herein referred to as ‘young regrowth’) was first cleared in 1968 by pulling and was later re-pulled in the early 1980s. Mean annual rainfall is 578 mm, with December, the wettest month, receiving 76.5 mm on average.

Distributed parameter hydrology model (ANSWERS) applied to a range of catchment scales using rainfall simulator data II: Application to spatially uniform catchments

The ANSWERS model, modified to include Green and Ampt infiltration, was tested using measured runoff from several tilled, black earth catchments on the eastern Darling Downs, Queensland. Rainfall and runoff data from rainfall simulator plots (1 m 2 and 88 m 2), and three small catchments (0.07 ha, 0.2 ha and 3.2 ha) were used to test predictions of runoff. Important infiltration parameter values were determined from a separate set of 1 m2 rainfall simulator plots. Other parameter values were measured directly or estimated from published sources. Measured runoff from the simulator plots and catchments was accurately predicted by the modified ANSWERS; a linear regression explained 93% and 81% of the variation between predicted and measured peak runoff rate and runoff volume, respectively. Runoff was accurately predicted with the modified ANSWERS, as processes controlling runoff from the catchments, including infiltration and routing of runoff, were realistically characterised. This allowed parameter values to be derived independently of runoff, and transported to different size catchments without distortion or optimisation.

Effects of initial water content and soil mechanical strength on the runoff erosion resistance of clay soils

Effects of antecedent water content and soil strength on the resistance to erosion by overland (rill) flow were tested for two clay soils of the eastern Darling Downs, Queensland. Both shear and unconfined compressive strength of wet soil (for soil wet to saturation immediately prior to application of rill flow) mere higher for soil with initially high water contents than for soil initially air-dry. Rates of runoff erosion did not show a simple relationship with soil strength across the two soils, though for each soil, higher strength was associated with much lower rates of erosion. The results show that variations in initial water content can be associated with large chang;es in soil erodibility. Particularly for the initially wet soils of higher strength, rates of runoff erosion were controlled by rates of detachment of sediment. From size distributions of wet aggregates and of sediment, and from measured water contents of wet soil, it can be suggested that the extent of incipient failure of aggregates on wet;ting was a major factor controlling ease of detachment by rill flow, as it can be inferred that detachment of sediment involved breakdown of aggregates. Consistent with this, rates of runoff erosion across the two soils showed a direct relationship with the amount of water uptake on wetting, which appears to be a useful measure of susceptibility to detachment by rill flow. Water uptake on wetting would be an indirect measure of incipient failure and, hence, of aggregate strength.

Using spatial land resource data and computer simulation modelling to evaluate sustainability of wheat cropping for a portion of the eastern Darling Downs, Queensland

Using spatial land resource data and computer simulation modelling to evaluate sustainability of wheat cropping for a portion of the eastern Darling Downs, Queensland

Ecology of Barley Yellow Dwarf Virus in South-East Queensland.

Transmission tests with Rhopalosiphum padi and R. maidis were used to assess incidence of barley yellow dwarf virus in cereal and grass specimens collected in surveys over the eastern Darling Downs and Lockyer district of Oueensland. Up to 20% incidence was found in randomly sampled, grazed oats, but incidence in wheat was less than 1%. Bromus catharticus was shown to be a perennial host of PAV and R. Padi. RMV incidence in Urochloa panicoides was up to 60% in early summer and Paspalurn dilatatum was a perennial host of RMV.

Study of soil erosion on vertisols of the eastern Darling Downs, Queensland. I. Effects on surface conditions on soil movement within contour bay catchments : Freebairn, D M; Wockner, G H Aus J Soil ResV24, N2, 1986, P135–158

Study of soil erosion on vertisols of the eastern Darling Downs, Queensland. I. Effects on surface conditions on soil movement within contour bay catchments : Freebairn, D M; Wockner, G H Aus J Soil ResV24, N2, 1986, P135–158

Effects of catchment management on runoff, water quality and yield potential from vertisols

To determine the effect of soil surface cover and antecedent moisture on catchment yield of water and sediment; runoff, soil moisture, and soil erosion were monitored on vertisols at two sites on the eastern Darling Downs, Qld., Australia. Stubble or crop cover reduced runoff volumes by 40% and peak discharge rates by 70–85% compared to bare soil. Contour banks trapped 80–90% of the eroded soil from paddocks. Suspended sediment discharged from contour banks into grassed waterways was reduced from a mean of 1.3% from bare soil to 0.2% where stubble was retained as a surface mulch. Cropping patterns planned to maximise the use of available soil water and rainfall reduced runoff. Using a water balance model to predict long-term runoff, it was shown that farm dams can be used to store a signifiant portion of the excess rainfall for later irrigation use while reducing total runoff and peak discharges. The combination of techniques viz. contour banks, stubble retention, optimised crop water use patterns and on-farm water storage significantly reduce flood flows and improve water quality from upland catchments, as well as improving productivity. Results from this study are directly relevant to many cracking clays in the semi-arid tropics.

A study of soil erosion on vertisols of the eastern Darling Downs, Queensland .II. The effect of soil, rainfall, and flow conditions on suspended sediment losses

Runoff water was sampled as it discharged through weirs installed at the outlet of 1 ha contour bay catchments. Cover, rainfall intensity, and soil tilth were important factors determining the concentration of suspended sediment in runoff. Mean delivery ratios for a grey clay, and a black earth, were 0.19 and 0.13 respectively. Contour banks reduced sediment loads reaching the bottom of slopes by at least six-fold. Three methods of calculation of total sediment loss were assessed. It was found that a flow-weighted mean of rising stage samples, and the arithmetic mean of sequential samples, were adequate in most cases for determining sediment losses. However, sequential samples weighted for discharge between samples were necessary for reliable measurements, especially during complex events.

A study of soil erosion on vertisols of the eastern Darling Downs, Queensland .I. Effects of surface conditions on soil movement within Contour Bay catchments

Effects of soil surface conditions on runoff and soil loss were studied on two major cracking clay soils of the Darling Downs, Queensland. Techniques used to measure soil loss between field contour bays under natural rainfall are described, and the results from 10 contour bay catchments (66 plot years) are presented. Soil movement was separated into rill, interrill, suspended sediment and channel deposition. Two slope lengths were considered (60 and 35 m), and interrill erosion appeared to be the major source of soil loss. Runoff and sediment concentration were both inversely related to surface cover and total soil movement was greatly reduced by surface cover. In an annual winter-wheat, summer-fallow system, removal of stubble resulted in soil movement of 29-62 t ha-1 year-1. Retention of stubble (stubble mulching) reduced soil movement to less than 5 t ha-1 year-1. Greater than 75% of the variance in soil movement from single events was explained by surface cover and peak runoff rate. Surface cover is a measure of the surface area protected from soil detachment and entrainment. Peak runoff rate describes the amount of energy or stream power available for detachment and entrainment.

Comparative effects of black and green gram (mung beans) and grain sorghum on soil mineral nitrogen and subsequent grain sorghum yields on the Eastern Darling Downs

A field trial was carried out on a black earth (Waco series) at Cambooya on the Eastern Darling Downs to compare the effect of black gram, green gram, grain sorghum and a summer fallow on soil mineral nitrogen (NO3-N + NH4-N) and the yield of grain sorghum grown in the following summer. The initial sorghum treatment severely depleted soil mineral nitrogen to 120 cm; even after a 173-d fallow, there was still 34 kg/ha less nitrogen present than initially in this treatment. Black and green gram also reduced levels of soil mineral nitrogen during crop growth, but these recovered to exceed pre-trial levels by 29 and 42 kg N/ha, respectively, after a winter fallow. The fallow treatment accumulated 100 kg N/ha of mineral nitrogen between January and October, but mineralization was markedly reduced from August to October. Sorghum grown on all plots in the second summer responded markedly to prior treatments, and grain yields and responses to nitrogen applied at 0, 34 and 68 kg N/ha reflected mineral nitrogen levels at planting. Yields of sorghum grain obtained without fertilizer after black gram, green gram and fallow were 8333, 7477 and 9663 kg/ha, respectively, compared with 4658 kg/ha after sorghum. Prior crops of both grams increased sorghum yield as much as a fertilizer application of 68 kg N/ha.

The taxonomy and distribution of Macropus (Fissuridon) pearsoni (Marsupialia: Macropodidae).

Macropus pearsoni, previously known only from the Pleistocene eastern Darling Downs, Queensland, is now recorded from the early Pleistocene Kanunka local fauna of the Katipiri Sands, South Australia. The presence of M. pearsoni as well as other species of macropodids in both the Darling Downs and Kanunka deposits may indicate a close temporal relationship between the faunas from these two localities. Fissuridon Bartholomai, 1973, appears to be a junior synonym of Macropus Shaw, 1790, but is retained as a subgeneric name and expanded to include Macropus (Fissuridon) pan DeVis, 1895.

Estimation of the plant available water capacity of a soil profile

The plant available water capacity (PAWC) was measured for a range of soils (black earths, grey, brown and red clays, krainozems, yellow earths and solodized solonetz/solodics) used for dryland agriculture in the uplands of th,- eastern Darling Downs of Queensland. Using these data, two one-parameter models - one based on the electrical conductivity profile and the other on observable profile features - were derived for estimating the PAWC of the soil profile. The electrical conductivity profile model reliably estimated the PAWC for black earths and grey, brown and red clays. In the case of the deep, black earths, it accounted for 90% of the variation. The observable profile feature model reliably estimated the PAWC for black earths and grey, brown and red clays and in the case of the grey, brown and red clays accounted for 88% of the variation. The models for the solodized solonetz/solodics were not significant. In addition the profile feature model provided estimates of PAWC for the krasnozems (grouped with black earths) and for the yellow earths and solodized solonetz/solodics as a group. An alternative technique for the estimation of PAWC for krasnozems and yellow earths is also presented. The techniques will provide a rapid first appraisal of the PAWC of a soil profile.

Surface runoff experiments on the eastern Darling Downs

Rainfall and runoff were measured from 1976 to 1980 on four 1 ha catchments at Greenmount, about 25 km south of Toowoomba, to study the effects of crop and residue management practices. For the first 2 years, three cropping strategies were carried out - summer cropping, winter cropping, and double cropping. In the following 2 years, four summer fallow conditions and a summer crop were used in the experiment. On average, about 4% of rainfall became runoff, and this was highly variable from storm to storm and among the surface treatments. U.S. Department of Agriculture curve numbers were calculated for each occurrence of runoff and grouped according to stubble management practice. For low, medium and high antecedent moisture, curve numbers averaged 70, 82 and 95 where stubble was burnt, compared with 55, 65 and 75 where stubble was incorporated or mulched. Time of concentration of the catchments was found to be in the order of 10-15 min from studies of unit hydrographs and rational method runoff coefficients. Runoff coefficients varied with amount of surface cover and rainfall intensity, and were in the same range of values found elsewhere in Australia. A multiple linear regression was derived to relate runoff coefficient to surface cover and rainfall intensity. The highest observed runoff rates from the experiment were used to check estimates of design flood flows from the procedures in the Queensland Soil Conservation Handbook and in 'Australian Rainfall and Runoff. The estimates from these design manuals compared very well with the recorded data.

Field calibration of a soil sulfate test on sward lucerne on the eastern Darling Downs, Queensland

The relation between phosphate-extractable sulfate and the response of lucerne to applied sulfur was examined on 20 established lucerne (Medicago sativa) swards on the black earths of the Darling Downs. Two rates of S were used (0.100 kg ha-1) and soil depths to 90 cm were considered. Six sites responded at the first cut and relative yield of lucerne was correlated with soil sulfate. The best fit of the data was obtained using a square root quadratic model and sulfate in the 0-80 cm zone. The critical soil level was 3.5 ppm. Of 17 attributes examined, only chloride concentration (0-60 cm) and conductivity of the soil water suspension (0-60 cm) significantly improved the variance in relative yield explained, but this was considered to be fortuitous. The relative importance of sub-soil sulfate (40-80 cm) to lucerne nutrition on these soils is shown.

The status of the taxa of extinct giant wombats (Vombatidae: Marsupialia), and a consideration of vombatid phylogeny.

A re-examination of the type material and the description of a recently discovered fossil specimen from the Pleistocene deposits of the eastern Darling Downs, Queensland, has supported the synonomy of two taxa of large extinct wombats, Phascolomys curvirostris Owen, 1875 and Phascolomys magnus Owen, 1872 in Ramsayia magna (Owen). This species is shown to be variable in size, but occasionally as large as the equally variable Phascolonus gigas. A mandible, also from the eastern Darling Downs, is referred to this species, while its similarity to the holotype of Phascolonus lemleyi Archer, suggests that this latter species should also be placed in Ramsayia. A revised generic diagnosis is included. A hypothesis of the relationships of living and fossil wombats is presented, based on a cladistic analysis of dental and palatal characters.

Liveweight response following sodium chloride supplementation of beef cows and their calves grazing native pasture

Hereford cattle grazing native pastures on the eastern Darling Downs, Queensland, were deemed sodium (Na) deficient on the basis of salivary Na and potassium (K) levels. Common salt (NaCl) was offered ad libitum to one half of the animals. Cows receiving the supplement had significantly better rates of liveweight increase (0.35 v. 0.14 kg head-1 day-1, P < 0.01) than unsupplemented cows. Calves of supplemented cows grew significantly faster than calves of unsupplemented cows (0.77 v. 0.62 kg head-1 day-1, P < 0.01). After 21 days of Na supplementation, cows in the supplemented group had mean saliva values of 139.1 m-equiv l-1 Na and 7.4 m-equiv l-1 K; these values are considered normal. Corresponding values in the unsupplemented group were 60.2 m-equiv l-1 Na and 71.7 m-equiv l-1 K, which are indicative of severe Na deficiency. Levels of this magnitude remained throughout the duration of the experiment. Blood and milk concentrations of Na and K were not affected by Na intake. Urinary levels of Na and K were attered by Na intake but were extremely variable.

Sulpur deficiency of dry land lucerne in the eastern Darling Downs of Queensland

Experiments to study the phosphorus, molybdenum and sulphur requirements of lucerne swards were conducted at six sites on the eastern Darling Downs, Queensland. The soils at all sites were derived from basalt. The swards did not respond to phosphorus at any of the sites and responded to molybdenum at only one. Sulphur deficiency was more severe in late winter-early spring than in summer. Lucerne response to added sulphur was not related to total soil sulphur and only partly related to available soil sulphur or water soluble soil sulphate. Five lucerne swards on black earths showed decreasing sulphur deficiency with increasing soil depth and increasing soil salinity. On one site annual medics were more severely affected by sulphur deficiency than was the deeper rooting lucerne.