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1
Dwyer, John M. "Reproductive size thresholds and seedling survival in Acacia harpophylla (Mimosaceae)." Australian Journal of Botany 65, no. 5 (2017): 438. http://dx.doi.org/10.1071/bt17051.
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Acacia harpophylla F.Muell. ex Benth. (brigalow) forests and woodlands formerly occupied at least 8.7 M ha of Queensland and New South Wales, but less than 10% persists in isolated fragments and linear strips within a matrix of exotic beef pasture and dryland cropping. Given the relatively rapid and widespread clearing of brigalow forests, recent research has focussed on restoration via naturally resprouting vegetation. However, our understanding of A. harpophylla sexual reproduction and seedling recruitment remains poor. This study, undertaken following a widespread masting event in late 2007, aimed to (1) quantify initial densities of A. harpophylla germinants; (2) estimate subsequent seedling survival during the first year; and (3) determine minimum size thresholds for sexual reproduction in A. harpophylla. Initial densities averaged >46 000 seedlings ha–1, but only 438 seedlings ha–1 (<1%) were estimated to remain after a year. Although mortality was high, seedling recruitment is probably still sufficient to replace senescing stems and augment population genetic diversity to some extent. A reproductive size threshold of 10 cm diameter was identified, providing useful information to predict when naturally resprouting stands will begin to participate in masting events.
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SCANLAN, J. C. "Woody overstorey and herbaceous understorey biomass in Acacia harpophylla (brigalow) woodlands." Austral Ecology 16, no. 4 (December 1991): 521–29. http://dx.doi.org/10.1111/j.1442-9993.1991.tb01081.x.
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Dwyer, John M., and Riah Mason. "Plant community responses to thinning in densely regenerating Acacia harpophylla forest." Restoration Ecology 26, no. 1 (May 29, 2017): 97–105. http://dx.doi.org/10.1111/rec.12536.
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Reichman, S. M., S. M. Bellairs, and D. R. Mulligan. "The effects of temperature and salinity on Acacia harpophylla (brigalow) (Mimosaceae) germination." Rangeland Journal 28, no. 2 (2006): 175. http://dx.doi.org/10.1071/rj06027.
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Acacia harpophylla F. Muell. (brigalow) used to naturally occur over a range of about 50 000 km2 in Queensland and New South Wales, Australia. Large scale clearing for agriculture has reduced the area to less than 20 000 km2 and it is estimated that 20–25% of vertebrate fauna living in brigalow communities will become locally extinct as a result of the current clearing induced loss of habitat. Some coal mining companies in central Queensland have become interested in providing habitat for the endangered bridle nail-tailed wallaby that lives in brigalow vegetation. However, there is little known about establishment techniques for brigalow on mine sites and other disturbed ground; an understanding of brigalow biology and ecology is required to assist in the conservation of this threatened vegetation community and for re-creation of bridled nail-tail wallaby habitat in the post mining landscape. Brigalow is an unusual species of Acacia because it is not hard-seeded and germinates readily without the need to break seed-coat imposed dormancy. Germination trials were undertaken to test the ability of brigalow seed to germinate with a range of temperatures and salinity levels similar to those experienced in coal mine spoil. Optimum germination was found to occur at temperatures from 15 to 38°C and no germination was recorded at 45°C. Brigalow was very tolerant of high salt levels and germinated at percentages greater than 50% up to the highest salinity tested, 30 dS/m. Germination of greater than 90% occurred up to an electrical conductivity of 20 dS/m. The results indicate brigalow seed can be sown in summer when rains are most likely to occur, however, shading of the seed with extra soil or mulch may ensure the ground surface does not become too hot for germination. Because of its ability to germinate at high salinity levels, brigalow may be suitable for use in saline mine wastes which are common on sites to be rehabilitated after mining.
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Kaur, K., R. K. Jalota, D. J. Midmore, and J. Rolfe. "Pasture production in cleared and uncleared grazing systems of central Queensland, Australia." Rangeland Journal 27, no. 2 (2005): 143. http://dx.doi.org/10.1071/rj05012.
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Clearing land of trees and introducing exotic pastures to enhance pasture and cattle production and hence enterprise financial performance are widely practised in Queensland. The results from many previous studies on tree clearing have emphasised the gains in pasture production, but over periods of less than 10–15 years after clearing. The present study questioned the sustainability of pasture production in cleared systems over a longer time-frame (>10 years of clearing). For this, three different age groups of clearing i.e. 5 year, 11–13 year and 33 year were selected in each of 3 major types of tree communities i.e. Eucalyptus populnea, E. melanophloia and Acacia harpophylla in central Queensland. Paired comparisons of cleared and uncleared (intact) pasture systems were selected for each age group of clearing. The results suggest that the initial gains in pasture production upon clearing were compatible with published studies. However, for longer periods of time since clearing, the gains in pasture production were not sustained and were accompanied by risks of land degradation and loss of pasture plant diversity. For E. populnea and A. harpophylla, the maximum benefits from clearing were achieved at 13–15 years whereas for E. melanophloia, any benefits existed only over a short period of 5–6 years. The study emphasises that each tree community exhibits a specific response with regard to the duration of increased pasture production following clearing. To estimate the total benefits from tree clearing in pasture development, it is important to consider both monetary benefits and non-monetary losses from clearing for different types of tree communities.
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Eastwood, Rod, Michael F. Braby, Daniel J. Schmidt, and Jane M. Hughes. "Taxonomy, ecology, genetics and conservation status of the pale imperial hairstreak (Jalmenus eubulus) (Lepidoptera:Lycaenidae): a threatened butterfly from the Brigalow Belt, Australia." Invertebrate Systematics 22, no. 4 (2008): 407. http://dx.doi.org/10.1071/is06028.
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The taxonomic status of Jalmenus eubulus Miskin stat. rev. is revised and considered to be specifically distinct from J. evagoras (Donovan) based on fundamental differences in morphology, ecology and genetics. Miskin’s holotype is fixed by monotypy and illustrated, with type locality Rockhampton, Queensland. Fixed differences in the mitochondrial genomes of J. eubulus and J. evagoras in which the mean pairwise divergence is only 0.85% indicate absence of matrilineal gene flow, whereas allozyme data show significant structure within and between populations of both species consistent with recent diversification. Underlying causes for the observed genetic patterns are investigated. The two species are parapatric, with a narrow range of overlap along the Great Escarpment in south-eastern Queensland. Jalmenus eubulus is restricted to vegetation communities comprising brigalow-dominated old-growth open-forests and woodlands in the Brigalow Belt (with larvae monophagous on Acacia harpophylla F. Muell. Ex Benth), whereas J. evagoras occurs in a range of disturbed eucalypt woodlands/open-forests predominantly in montane and coastal areas east of this bioregion (with larvae polyphagous on Acacia species other than A. harpophylla). The conservation status of J. eubulus is considered to be vulnerable nationally and critically endangered in New South Wales according to International Union for Conservation of Nature (IUCN) criteria. Nationally, the geographic range has an estimated area of occupancy of less than 2000 km2, is severely fragmented, and the extent or quality of its habitat, which is poorly conserved, continues to decline. It is recommended that the taxon be used as an indicator for identification of remnant old-growth forest for conservation planning, as well as a flagship for the conservation of invertebrate biodiversity associated with this threatened ecological community.
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Thornton, C. M., B. A. Cowie, D. M. Freebairn, and C. L. Playford. "The Brigalow Catchment Study: II. Clearing brigalow (Acacia harpophylla) for cropping or pasture increases runoff." Soil Research 45, no. 7 (2007): 496. http://dx.doi.org/10.1071/sr07064.
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The Brigalow Catchment Study (BCS) was established to determine the impact on hydrology when brigalow land is cleared for cropping and grazing. The paired catchment study was commenced in 1965 using catchments of approximately 15 ha, with natural vegetation dominated by brigalow scrub (Acacia harpophylla). Three contiguous catchments were selected near Theodore in central Queensland to represent the extensive brigalow bioregion of central and southern Queensland and northern New South Wales (~40 Mha). The hydrology of the 3 catchments was characterised during a 17-year calibration period (1965–81). The catchments were considered hydrologically similar, with sufficient data available for an empirical comparison between catchments. In 1982, two of the catchments were cleared, with one developed for cropping and the other sown to improved pasture. The third catchment was used as an uncleared control. Hydrologic characteristics were then compared for the following 21 years. In their virgin state, the catchments behaved similarly, with average annual runoff being 5% of annual rainfall. Once cleared, total runoff from the cropping catchment increased to 11% of annual rainfall and total runoff from the pasture catchment increased to 9% of annual rainfall; however, timing of the individual runoff events varied between land uses. In order to confirm that changes in hydrology were a function of land use and not just seasonal variability or sampling error, several analytic techniques were used: a simple comparison of runoff totals, comparison of events, comparison of probability of exceedance for daily runoff, and comparison of predicted and observed runoff using a water balance modelling approach.
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Johnson, Robert W., William J. McDonald, Roderick J. Fensham, Clive A. McAlpine, and Michael J. Lawes. "Changes over 46 years in plant community structure in a cleared brigalow (Acacia harpophylla) forest." Austral Ecology 41, no. 6 (April 22, 2016): 644–56. http://dx.doi.org/10.1111/aec.12354.
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Le Brocque, Andrew F., and Peter M. Wagner. "Passive brigalow (Acacia harpophylla) woodland regeneration fails to recover floristic composition in an agricultural landscape." Austral Ecology 43, no. 4 (February 6, 2018): 409–23. http://dx.doi.org/10.1111/aec.12578.
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Machado, Paulo Fernando Dos Santos, José Newton Cardoso Marchiori, and Anelise Marta Siegloch. "Anatomia da madeira de seis espécies exóticas do gênero Acacia Mill. (Fabaceae)." Balduinia, no. 49 (August 24, 2015): 01. http://dx.doi.org/10.5902/2358198019214.
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As madeiras de Acacia acuminata A. Gray, Acacia cambagei R.T. Baker, Acacia harpophylla F. Muell. Ex Benth., Acacia koa A. Gray, Acacia rhodoxylon Maiden e Acacia richii A. Gray são anatomicamente descritas e ilustradas com fotomicrografias. Todas as seis espécies apresentam os seguintes caracteres de ampla ocorrência em Fabaceae: porosidade difusa; placas de perfuração simples; elementos vasculares com pontoações ornamentadas; parênquima paratraqueal; raios homogêneos; e fibras libriformes não septadas. O último destes caracteres permite distinguir as mesmas do gênero Senegalia Raf., segregado de Acacia Mill. em 2005. Por sua vez, a ausência de grandes raios conspícuos, juntamente com a abundância de séries parenquimáticas axiais com mais de três células de altura, permitem excluir as seis espécies do gênero Vachellia Wight & Arn
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BROWN, DANNY, JESSICA WORTHINGTON WILMER, and STEWART MACDONALD. "A revision of Strophurus taenicauda (Squamata; Diplodactylidae) with the description of two new subspecies from central Queensland and a southerly range extension." Zootaxa 3243, no. 1 (March 22, 2012): 1. http://dx.doi.org/10.11646/zootaxa.3243.1.1.
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The Golden-tailed Gecko, Strophurus taenicauda (De Vis 1886), is redescribed and two new subspecies from centralQueensland are diagnosed on the basis of scalation, colour pattern and genetic differences. The distribution of S. t. taeni-cauda comprises the south-eastern part of the Queensland Brigalow Belt bioregion. Strophurus taenicauda albiocularisssp. nov. occupies the northern half of the range whilst S. taenicauda triaureus ssp. nov. has a limited range in the centraleastern part of the Brigalow Belt. The two new subspecies are predominantly inhabitants of Eucalyptus woodlands andare not as restricted to Brigalow (Acacia harpophylla) woodlands as S. t. taenicauda. A single record of the nominate subspecies from northern New South Wales is also reported, extending the range of the species by >250km.
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Thornton, C. M., and B. Yu. "The Brigalow Catchment Study: IV. Clearing brigalow (Acacia harpophylla) for cropping or grazing increases peak runoff rate." Soil Research 54, no. 6 (2016): 749. http://dx.doi.org/10.1071/sr15121.
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In Queensland, Australia, large tracts of native vegetation have been cleared for agriculture, resulting in substantial hydrological changes in the landscape. Australia’s longest-running paired catchment study, the Brigalow Catchment Study (BCS), was established in 1965 to monitor hydrological changes associated with land development, particularly that of the 1960s Land Development Fitzroy Basin Scheme. The BCS has unequivocally shown that developing brigalow (Acacia harpophylla) for cropping or for grazing doubles runoff volume. However, to date little research had been undertaken to quantify the changes in peak runoff rate when brigalow is cleared for cropping or grazing. The present study compared peak runoff rates from three brigalow catchments, two of which were subsequently cleared for cropping and pasture. Prior to land development, average peak runoff rates from the three brigalow scrub catchments were 3.2, 5 and 2mmh–1 for catchments 1 to 3 respectively. After development, these rates increased to 6.6mmh–1 from the brigalow scrub control catchment (catchment 1), 8.3mmh–1 from the cropping catchment (catchment 2) and 5.6mmh–1 from the pasture catchment (catchment 3). Peak runoff rate increased significantly from both the cropping and pasture catchments after adjusting for the underlying variation in peak runoff rate due to climatic variation between the pre- and post-development periods. The average peak runoff rate increased by 5.4mmh–1 (96%) for the cropping catchment and by 2.6mmh–1 (47%) for the pasture catchment. Increases in peak runoff rate were most prevalent in smaller events with an average recurrence interval of less than 2 years under cropping and 4 years under pasture.
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Yates, DJ. "Short-Term Changes in Spectral Properties of Phyllodes of Brigalow (Acacia harpophylla F Muell Ex Benth) in Response to Wetting." Australian Journal of Botany 40, no. 1 (1992): 27. http://dx.doi.org/10.1071/bt9920027.
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The phyllodes of Acacia harpophylla (brigalow) possess a high reflectivity (0.20) in the visible wavelengths due to the presence of a dense covering of flattened trichomes. This results in a low value for phyllode absorptivity (0.79). While dry phyllodes appear grey-blue to the eye, wet phyllodes appear green and their reflection spectra are similar to those of 'typical' foliage elements. When wet, reflectivity in the visible wavelengths is reduced (0.09) and absorptivity is increased by 14%. Examination of the wetting and drying process, both visually and by measuring the time course of reflectivity, illustrates the importance of the wettable surfaces of both the epidermis and the individual trichomes. On drying, the reflectivity increase in the near infrared (NIR, 0.41-0.59) precedes that in the visible portion of the spectrum, although changes in the visible portion of the spectrum are larger than those in the NIR.
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Arnold, Sven, Yolana Kailichova, and Thomas Baumgartl. "Germination ofAcacia harpophylla(Brigalow) seeds in relation to soil water potential: implications for rehabilitation of a threatened ecosystem." PeerJ 2 (February 25, 2014): e268. http://dx.doi.org/10.7717/peerj.268.
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Collard, Stuart J., Andrew F. Le Brocque, and Charlie Zammit. "Effects of local-scale management on herbaceous plant communities in Brigalow (Acacia harpophylla) agroecosystems of southern Queensland, Australia." Agriculture, Ecosystems & Environment 142, no. 3-4 (August 2011): 176–83. http://dx.doi.org/10.1016/j.agee.2011.05.001.
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Midgley, David J., Jennifer A. Saleeba, Michael I. Stewart, and Peter A. McGee. "Novel soil lineages ofArchaeaare present in semi-arid soils of eastern Australia." Canadian Journal of Microbiology 53, no. 1 (January 1, 2007): 129–38. http://dx.doi.org/10.1139/w06-104.
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The diversity of Archaea was studied in vertisolic and loam soils of a semi-arid region in Australia. Sampling was undertaken at an agricultural site, two grassland environments, and a brigalow (Acacia harpophylla) woodland. Archaeal community structure was profiled using amplified ribosomal DNA restriction analysis (ARDRA) combined with rDNA sequencing of an example of each restriction fragment length polymorphism type. Sequence comparison and phylogenetic analysis demonstrated that both crenarchaeotal and euryarchaeotal Archaea were present at oxic depths in the soil at all field sites. Along with previously described soil archaeal lineages, novel soil lineages and the deeply divergent Pendant-33 group of Euryarchaeota were also detected. A novel statistical method for comparing ARDRA derived data was demonstrated and implemented using the archaeal communities from the four field sites. Archaeal diversity, as measured by this method, was significantly higher in the agricultural site than at either of the grassland sites or the brigalow woodland.Key words: archaeal communities, cotton, Euryarchaeota, Crenarchaeota, soil.
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Grace, PR, IC MacRae, and RJK Myers. "Factors influencing the availability of mineral nitrogen in clay soils of the brigalow (Acacia harpophylla) region of Central Queensland." Australian Journal of Agricultural Research 43, no. 5 (1992): 1197. http://dx.doi.org/10.1071/ar9921197.
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Microbiological and chemical assays were performed on clay soils from woodland (Acacia harpophylla-Casuarina cristata), grassland (Panicurn maximum var trichoglume-Chloris gayana) and cropland (Vigna mungo) in the brigalow region of Central Queensland. Over a 15 month period, the microbial biomass C in the top 3.5 cm of native brigalow woodland soil was on average 3630 8g C g-l, 50% more than an associated perennial pasture and over 400% more than an annually cropped soil. Microbial biomass N (575 8g N g-l) in woodland soil was on average 41% and 270% higher than in pasture and cropped soils respectively and highly correlated with seasonal soil moisture content. Viable counts of bacteria were consistently lower (average 69.2%) in the 0-3.5 cm and 3.5-7.5 cm strata of woodland soil compared with pasture and annual crop sites. Soil NO-3- N levels increased two fold in the upper 3.5 cm of the woodland site during low rainfall periods. This increase may be attributed to a more efficient distribution of mineral N mediated by the increased presence of a fungal population in this community. Leaching may also play a significant role in the distribution of plant available N in the brigalow region as suggested by the inverse relationship N = 54.11-0.67 R (P<0.01), where N is soil NO-3-N (8g N g-l) and R is rainfall in the preceding 3 month period (mm month-1).
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COLLARD, S., and C. ZAMMIT. "Effects of land-use intensification on soil carbon and ecosystem services in Brigalow (Acacia harpophylla) landscapes of southeast Queensland, Australia." Agriculture, Ecosystems & Environment 117, no. 2-3 (November 2006): 185–94. http://dx.doi.org/10.1016/j.agee.2006.04.004.
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Seabrook, Leonie, Clive McAlpine, and Rod Fensham. "Spatial and temporal analysis of vegetation change in agricultural landscapes: A case study of two brigalow (Acacia harpophylla) landscapes in Queensland, Australia." Agriculture, Ecosystems & Environment 120, no. 2-4 (May 2007): 211–28. http://dx.doi.org/10.1016/j.agee.2006.09.005.
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Poulton, P. L., N. I. Huth, and P. S. Carberry. "Use of simulation in assessing cropping system strategies for minimising salinity risk in brigalow landscapes." Australian Journal of Experimental Agriculture 45, no. 6 (2005): 635. http://dx.doi.org/10.1071/ea03250.
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Areas of brigalow (Acacia harpophylla) dominated landscapes in north-eastern Australia have declined drastically due to major clearing and agricultural expansion during the late 1940s and early 1960s. The inherently high salt content of the soils of this region present a potential downstream salinity hazard from groundwater recharge. Chronosequence analysis using paired chloride profiles from soil cores taken beneath brigalow remnants and adjacent pasture or cropping lands provide a tracer for quantifying historic recharge rates as a consequence of vegetation management and agricultural practice. Present day chloride levels are the direct result of past land management. In this paper we present the results of simulation studies used to benchmark historic management practice since clearing in terms of chloride leaching and drainage. These simulations estimated that 15.3 t/ha of chloride leached from the top 150 cm in 7 major drainage events (>15mm) over a 34-year period, and that these leaching events corresponded with peaks in rainfall cycles. Use of virtual experiments to investigate alternative cropping systems found significant increases in the frequency and magnitude of drainage events of no-tillage wheat compared with sorghum grown in a summer-rainfall region. Systems simulation can provide guidelines for designing cropping systems which best balance production with drainage objectives in dryland farming systems.
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LEPAIS, OLIVIER, and CECILE F. E. BACLES. "Comparison of random and SSR‐enriched shotgun pyrosequencing for microsatellite discovery and single multiplex PCR optimization in Acacia harpophylla F. Muell. Ex Benth." Molecular Ecology Resources 11, no. 4 (March 16, 2011): 711–24. http://dx.doi.org/10.1111/j.1755-0998.2011.03002.x.
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Clem, RL, and TJ Hall. "Persistence and productivity of tropical pasture legumes on three cracking clay soils (Vertisols) in north-eastern Queensland." Australian Journal of Experimental Agriculture 34, no. 2 (1994): 161. http://dx.doi.org/10.1071/ea9940161.
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There are few commercial legumes available for sowing on the cracking clay soils of northeastern Queensland, where legumes are needed to improve quality of perennial native grass pastures and to arrest nitrogen decline in cropping land. To evaluate introduced legumes from heavy-textured soils, a replicated row experiment was established in 3 environments to assess the adaptation of 56 accessions from 37 species (22 genera). The sites were on 3 dark cracking clay soils supporting the following grasslands: Dichanthium -Bothriochloa- Astrebla; Dichanthium aristatum; and Cenchrus ciliaris on cleared Acacia harpophylla (brigalow) country.The main selection criteria during the 4-year evaluation were persistence, regeneration, production, and spread, with green leaf retention, nutrient concentrations, and pest susceptibility also being considered. The perennial legumes Clitoria ternatea (CPI 47 187 and CPI 49963), Desmanthus virgatus (CPI 78373), Leucaena leucocephala (CPI 61227 and cv. Cunningham), Stylosanthes scabra (CPI 55868), and Indigofera schimperi (CPI 69495), and annuals Centrosema pascuorum (CPI 55697), Desmodium dichotomum (CPI 47 186), and Vigna trilobata (CPI 47510), showed promise as pasture or short-term ley species for these clay soils (Vertisols) in subcoastal, north-eastern Queensland. Other species were identified that require evaluation of a wider range of genetic material. The role of perennial and annual sown legumes in pasture and cropping systems on these cracking clay soils is discussed.
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Stewart, GR, MH Turnbull, S. Schmidt, and PD Erskine. "13C Natural Abundance in Plant Communities Along a Rainfall Gradient: a Biological Integrator of Water Availability." Functional Plant Biology 22, no. 1 (1995): 51. http://dx.doi.org/10.1071/pp9950051.
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Carbon isotope natural abundance (δ13C) has been previously used as a powerful tool in the study of water-using processes at the leaf, individual and within-community levels. We analysed 348 species from 12 plant communities along a 900 km-long rainfall gradient in southern Queensland. Although the range of δ13C values found in a given community was large, variability in the δ13C signature of plants within a community was relatively small given the large numbers of species sampled (mean n per site of 29) and the taxonomic diversity in each. The community-averaged δ13C signature ranged from -25.60 in a brigalow (Acacia harpophylla) dominated community in western Queensland to - 31.20 in subtropical rainforest in eastern Queensland. A strong relationship was found between the δ13C value averaged for each site and rainfall within the range 350-1700 mm per annum. Foliar δ13C was also related to the number of rain days per annum and moisture balance (rainfall - evaporation). The strength of these relationships varied only slightly according to the rainfall parameter used, with values for r2 of 0.78, 0.70, 0.70 and 0.74 for the relationship between δ13C and long-term rainfall average, 5-year rainfall average, number of rain days and moisture balance, respectively. Despite considerable taxonomic variability within a given plant community, the averaged δ13C signature for that community gives a strong indication of moisture availability.
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Fensham, Roderick J., Jason Halford, Chris Hansen, Boris Laffineur, and Billie Williams. "Threatened species in a threatened ecosystem: the conservation status of four Solanum species in the face of ongoing habitat loss." Oryx 53, no. 3 (May 20, 2019): 439–49. http://dx.doi.org/10.1017/s0030605318001266.
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AbstractPlant biodiversity is threatened by habitat loss, fragmentation and invasion by exotic species, but the effects of these disturbances on individual plant species are rarely quantified. Since the 1950s, brigalow Acacia harpophylla forests in Australia have been extensively cleared and converted to pastures dominated by exotic grasses. Here we assess the habitat requirements, population numbers and threats for four poorly known bush tomato species, Solanum adenophorum, Solanum dissectum, Solanum elachophyllum and Solanum johnsonianum. Herbarium records and surveys demonstrated a strong association of all four species with brigalow habitat, although S. elachophyllum also occurred in other habitat. We derived historical and current population estimates from plant densities at current sites and the area of mapped brigalow habitat. Density estimates are imprecise because the survey data vary greatly, but the assessment indicates the populations of all four species have declined > 93%. Solanum dissectum and S. johnsonianum did not persist in cleared brigalow habitat, whereas S. adenophorum and S. elachophyllum had some capacity to persist in clearings. None of the species occur where the exotic grass cover is > 40%. Between 27% and 57% of the records of the four species are in brigalow remnants with a high edge-to-area ratio or open canopy (< 50% cover), making them highly vulnerable to invasive grasses. We recommend the categorization of S. dissectum and S. johnsonianum as Critically Endangered, S. adenophorum as Vulnerable and S. elachophyllum as Near Threatened.
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Sangha, Kamaljit K., Rajesh K. Jalota, and David J. Midmore. "Litter production, decomposition and nutrient release in cleared and uncleared pasture systems of central Queensland, Australia." Journal of Tropical Ecology 22, no. 2 (February 1, 2006): 177–89. http://dx.doi.org/10.1017/s0266467405003020.
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The temporal impact of clearing trees on litter production, litter decomposition and on C, N and P release through decomposition of litter was examined in the pasture systems of a semi-arid zone of central Queensland. Paired sites for cleared pastures (developed from clearing woodlands) and uncleared (intact woodland) pastures were selected to represent three dominant tree communities of the region i.e. Eucalyptus populnea, E. melanophloia and Acacia harpophylla, with three different time-since-clearing (5, 11–13 and 33 y) treatments. Yearly litter production was greater at uncleared sites (1732–1948 kg ha−1 y−1 for eucalypt and 2596 kg ha−1 y−1 for acacia communities) compared with cleared sites (1038–1282 kg ha−1 y−1 for eucalypt and 1100 kg ha−1 y−1 for acacia communities averaged over three time-since-clearing treatments). Rates of litter decomposition and of release of C, N and P from decomposing litter were higher at cleared than uncleared sites for all three tree communities. The cleared and uncleared sites did not differ significantly in total amount of C and N released per year since the concentrations of C and N were greater in litter from uncleared sites but the rate of release was less than that at cleared sites. Slow but continuous release of nutrients in eucalypt and acacia woodlands may be an adaptation of these communities to maintain the nutrient cycle and to avoid leaching of nutrients in the nutrient-poor soils of the region.
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Kaur, Kamaljit, David J. Midmore, Rajesh K. Jalota, and Nanjappa Ashwath. "Pasture composition in cleared and uncleared woodlands." Australian Journal of Botany 54, no. 5 (2006): 459. http://dx.doi.org/10.1071/bt05174.
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Land clearing in Queensland is often practised to enhance pasture production, and hence, increase financial returns from beef production. The benefits of clearing have been quantified in terms of short-term gains in pasture yield but have not adequately accounted for possible medium- or longer-term impediments that may be attributed to clearing. Therefore, impacts of clearing and the subsequent sowing of exotic grasses such as Cenchrus ciliaris L. on pasture composition and production were studied. To achieve this, paired sites were selected representing cleared and uncleared pastures across three different times since clearing (i.e. 5, 11–13 and 33 years since clearing) for the three dominant tree communities of central Queensland (i.e. Eucalyptus populnea F.Muell. (poplar box), E. melanophloia F.Muell. (silver-leaved ironbark) and Acacia harpophylla F.Muell. ex. Benth. (brigalow)). The results demonstrated that species diversity declined with clearing and sowing of exotic pastures. Species diversity and pasture production were negatively related. Although pasture yield was 2–3 times greater 13 years after clearing of E. populnea and A. harpohylla, the gains in pasture yield were not consistent over time, yields being only 1.5 times greater after 33 years of clearing. In E. melanophloia, an increase in the yield of only 1.5–1.8 times occurred 5 years after clearing compared with uncleared pastures, whereas 33 years after clearing, yield was 3/4 of that in uncleared pastures. The initial gains in pasture yield were accompanied by a loss of plant diversity that may affect ecosystem functions such as nutrient cycling or soil mineralisation, and the longer-term production gains.
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Sangha, Kamaljit K., Rajesh K. Jalota, and David J. Midmore. "Impact of tree clearing on soil pH and nutrient availability in grazing systems of central Queensland, Australia." Soil Research 43, no. 1 (2005): 51. http://dx.doi.org/10.1071/sr03152.
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In Queensland, land is cleared at high rates to develop pastures for enhanced production and the associated monetary gains. However, pasture production declines over time in cleared pastures until a new equilibrium is reached. The present study focussed on elucidating the reasons for decline in pasture production and finding the key soil properties that are affected due to clearing. Paired sites for cleared and uncleared pastures were selected to represent 3 dominant tree communities of the semi-arid tropics in central Queensland, i.e. Eucalyptus populnea, E. melanophloia, and Acacia harpophylla. The cleared pastures were chosen to represent 3 different durations of time since clearing (5, 11–13, and 33 years) to evaluate the temporal impact of clearing on soil properties. Various soil parameters were studied: macronutrients—available N (NH4+and NO3–), total N, and available P; micronutrients—Cu, Fe, Zn, and Mn; exchangeable cations—Ca, Mg, Na, and K (also macronutrients); pHw; and electrical conductivity. Of these, pHw showed a significant response to time of clearing for all 3 tree communities. Soil pHw increased significantly at cleared sites relative to uncleared (native woodland) pastures, and the increase was highly correlated with concentrations of exchangeable Ca, Mg, and Na. The change in soil pHw and exchangeable cations was more evident at >0.30 m soil depth. The increase in soil pHw in cleared pastures decreased the availability of soil nutrients for plant growth and, hence, pasture productivity. The interactions of different soil properties down the profile as a result of changes caused by clearing are important when interpreting the effects of clearing on soil properties.
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Catchpole, VR. "Nitrogen dynamics of oats, sorghum, black gram, green panic and lucerne on a clay soil in south-eastern Queensland." Australian Journal of Experimental Agriculture 32, no. 8 (1992): 1113. http://dx.doi.org/10.1071/ea9921113.
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Changes in the distribution of nitrate-nitrogen (N) in a clay soil (Pellustert) under oats (Avena sativa cv. Minhafer), sorghum (Sorghum bicolor cv. E57), black gram (Vigna mungo cv. Regur), green panic (Panicum maximum cv. Petrie), and lucerne (Medicago sativa cv. Hunter River), and the uptake of N into plant shoots, were measured at Narayen on the brigalow (Acacia harpophylla) lands of south-eastem Queensland over each cropping season in 1975-85. Nitrate-N accumulated in the subsoil (30-150 cm) under sorghum and black gram, but not under oats. Green panic depleted nitrate-N after 2 years, and lucerne after 1 year. Losses of nitrate-N during 2 wet years reached 300 kg/ha under sorghum and black gram, and 57 kg/ha under oats, but were negligible under green panic and lucerne. Leaching to below 150 cm in the soil was the probable cause. The supply of soil N to oats, sorghum, and black gram was adequate during the 10 years, but the N yield of green panic decreased from 239 kg/ha to 150 kg/ha after 5 years. Accumulation of nitrate-N under sorghum and black gram could be utilised by rotating these crops with green panic or lucerne. This would also improve the productivity of green panic pastures. Rotating the summer crops with oats (winter crop) or with deeprooted crops (e.g. sunflowers) should also be tested. Alternatively, reduction of production of nitrate-N in the soil could be attempted. Zero or reduced tillage could do this, but it may also increase leaching by increasing the entry and movement of water in the soil.
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Shapcott, Alison, Robert W. Lamont, Gabriel Conroy, Heather E. James, and Yoko Shimizu-Kimura. "A genetic, demographic and habitat evaluation of an endangered ephemeral species Xerothamnella herbacea from Australia’s Brigalow belt." Australian Journal of Botany 65, no. 1 (2017): 38. http://dx.doi.org/10.1071/bt16148.
Full textAbstract:
Little remains of the Brigalow (Acacia harpophylla F.Muell. ex Benth.) woodlands of Australia, primarily due to land clearing for grazing and agriculture. Many threatened species in this region are poorly studied, and the life history traits of some herbaceous species such as ephemeral shoot systems, mean that conservation assessments are difficult. Recent gas pipeline developments have led to an increased need to understand the ecology and genetics of such taxa, in order to advise offset and translocation activities. Xerothamnella herbacea R.Baker is an endangered ephemeral herbaceous species from the Brigalow Belt region, which dies back during prolonged dry conditions. The aim of this study was to map the extent of potentially suitable habitat of this species, including determination of population extent within existing protected area estate. The species population sizes, reproductive activity and evidence of clonal spread, as well as the levels of genetic diversity and inbreeding, across the species range were also assessed to provide guidance for potential translocation and offsetting programs. The genetic results were related to the species suitable habitat distribution to test whether historic or recent habitat fragmentation most explains genetic patterns in this species. Most of the populations of this species were found to be small with less than 100 plants. The species appears not to be limited by its reproductive output, suggesting other factors may limit its abundance. The species populations have moderate to low genetic diversity suggesting the species is genetically viable in the medium term but are inbred which may be partially due to vegetative spread. Geographic proximity does not predict genetic similarity of populations and diversity is not correlated with population size. The results indicate potential translocation or offsetting programs need to account for genetic relationships in their planning. Resprouting ability has potentially assisted the species to slow the pace of genetic diversity loss due to anthropogenic fragmentation.
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Fensham, R. J., J. C. McCosker, and M. J. Cox. "Estimating Clearance of Acacia-dominated Ecosystems in Central Queensland Using Land-system Mapping Data." Australian Journal of Botany 46, no. 2 (1998): 305. http://dx.doi.org/10.1071/bt96129.
Full textAbstract:
Preferential clearance of productive Acacia-dominated ecosystems was determined using digital land-system mapping and a 1994–1995 native vegetation remnant coverage from central Queensland. The previously mapped land systems are composed of complexes of land units, covering a range of productive potentials that are not individually mapped but defined according to their proportions within the land systems. Some land units were grouped into 11 ‘Acacia ecosystems’ composed of unique combinations of geology and vegetation dominated by brigalow (Acacia harpophylla F.Muell. ex Benth.), gidgee (A. cambagei R.T.Baker) or blackwood (A. argyrodendron Domin). Calculation of the remnant area of these Acacia ecosystems, assuming equal proportions of vegetation clearance of the land unit components within the land-system complexes (equal proportion calculation), was compared with a more accurate calculation based on interpretation of aerial photography (aerial-photograph calculation) data. The aerial photograph calculation of remnant area was 44% of the equal proportion calculation for brigalow on Tertiary clay and the ratio between these calculations was greater than 100% for only one Acacia ecosystem of relatively low production potential. The proportion of the remnant Acacia ecosystems relative to less productive ecosystems on tenures assigned to production (leasehold and freehold) was consistently lower than on other tenures. The use of mapping consisting of composite ecosystems with various production potentials for area-based assessment of vegetation clearance will overestimate the remnant areas of the relatively productive types unless a procedure such as that outlined here is used to correct for preferential clearance. This study provides near-complete and accurate data on the 1994–1995 status of Acacia ecosystems in central Queensland. Relative to their original area, values ranged from 6.8% for brigalow on Tertiary clay to 37.6% for gidgee–blackwood on alluvium.
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Elledge, Amanda, and Craig Thornton. "Effect of changing land use from virgin brigalow ( Acacia harpophylla ) woodland to a crop or pasture system on sediment, nitrogen and phosphorus in runoff over 25 years in subtropical Australia." Agriculture, Ecosystems & Environment 239 (February 2017): 119–31. http://dx.doi.org/10.1016/j.agee.2016.12.031.
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Cowie, B. A., C. M. Thornton, and B. J. Radford. "The Brigalow Catchment Study: I. Overview of a 40-year study of the effects of land clearing in the brigalow bioregion of Australia." Soil Research 45, no. 7 (2007): 479. http://dx.doi.org/10.1071/sr07063.
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This paper describes a long-term, paired-catchment study, its broad findings, and considerations for future resource management of brigalow lands in north-eastern Australia. The Brigalow Catchment Study (BCS) commenced in 1965 with a pre-clearing calibration phase of 17 years to define the hydrology of 3 adjoining catchments (12–17 ha). After 2 catchments were cleared in 1982, 3 land uses (brigalow forest Acacia harpophylla, cropping, and grazed pasture) were monitored for water balance, resource condition and productivity, providing information for scientific understanding and resource management of the major land uses of the brigalow bioregion. In addition, this paper draws upon several project reviews to highlight the value of the BCS as an ‘outdoor laboratory’, its data resource, and to reflect on the study’s scientific rigor to support present and future value. An assessment of the BCS against national and international attributes of best practice for long-term studies showed the study to rate highly in aspects of design, implementation, monitoring, and data management, and moderately in formal publication, strategic management, and networking. The literature shows that Brigalow Catchment Study is the longest paired-catchment study in Australia, and continues to sample the interactions between climate, soils, water, land use, and management. Finally, this paper provides the context for component-specific papers on changes in hydrology, productivity, and salt balance. Results from the study to date include: a doubling of runoff after clearing, a reduction in wheat yield by more than 60% over 20 years, a halving of pasture availability 3 years after clearing, a decline in cattle liveweight gain of 4 kg/ha.year over an 8-year period with a constant stocking rate, and the leaching of 60% of the root-zone (0–1.5 m) chloride after clearing for cropping. Unanticipated applications of the data from the study include: (i) a crucial set of soil samples for calibration of the RothC soil carbon model used to estimate Australia’s soil carbon emissions; and (ii) estimates of deep drainage as a basis for salinity risk assessment in the region.
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Dalal, R. C., R. Eberhard, T. Grantham, and D. G. Mayer. "Application of sustainability indicators, soil organic matter and electrical conductivity, to resource management in the northern grains region." Australian Journal of Experimental Agriculture 43, no. 3 (2003): 253. http://dx.doi.org/10.1071/ea00186.
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Sustainability is a multifaceted concept. It is expressed here as 'to ensure that the past and current management and use of natural resources does not diminish their capacity to meet economic, environmental, social and aesthetic needs and opportunities of the present and future generations'. Sustainability indicators can be used to monitor responses in condition and trend as a result of natural resource management. We report here 2 case studies that demonstrate the significance of sustainability indicators in discerning trends in land and water resources in the southern Brigalow (Acacia harpophylla) Belt, a major region of the Queensland Murray–Darling Basin. First, soil organic matter was used as a sustainability indicator of soil productivity, soil aggregation, and its association with soil sodicity since these soil attributes affect infiltration rates, runoff and drainage. The second study involved comparing the trends in stream salinity (electrical conductivity) over 35 years and sustainability indicators for a dominant Vertosol in a region used for cereal cropping. Groundwater level and electrical conductivity of a long-term monitoring bore in the Dalby–Chinchilla region, were also analysed to discern trends in salinity and association of the groundwater with soil and stream salinity. Soil organic matter declined exponentially as the cultivation period for cereal cropping increased. This resulted in a reduction in soil nitrogen supply, and lower grain protein and cereal grain yields. The associated effects were reduced soil aggregation and increased soil sodicity. Electrical conductivity of the soil as well as stream water showed weak but declining trends with time. Groundwater level from the long-term monitoring bore near the stream and groundwater salinity showed significantly declining trends over the 35 years sampling period. Groundwater salinity was similar to the Vertosol electrical conductivity at 240–300 cm depths, suggesting groundwater connectivity to the overlaying soil. Thus, use of sustainability indicators provided a strong association among the various attributes of the landscape. However, it is still a challenge to integrate the various sustainability indicators in a landscape context, integrated over space (spatial and geographical distribution), attributes (quality characteristics) and time (trend).
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Page, K. L., R. C. Dalal, N. W. Menzies, and W. M. Strong. "Subsoil nitrogen mineralisation and its potential to contribute to NH4 accumulation in a Vertosol." Soil Research 41, no. 1 (2003): 119. http://dx.doi.org/10.1071/sr02038.
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High concentrations of NH4+ (up to 270 kg N/ha) have been observed in a Vertosol below 1 m depth in south-east Queensland. This study examined the possibility that mineralisation associated with the removal of native vegetation (Acacia harpophylla) for cropping was responsible for the production of NH4+. Particularly, the potential contribution of decomposing root material and/or dissolved organic nitrogen (DON) leached into the subsoil after clearing was investigated. The amount of N that was contained within native vegetation root material was determined from an area of native vegetation adjacent to the cleared site containing elevated NH4+ concentrations. In addition, the amount of NH4+ that could be mineralised in the native vegetation soil was determined by monitoring NH4+ concentrations over 360 days in intact cores, and by conducting waterlogged incubations. To determine the rate at which a source of DON leached into the subsoil would mineralise, soil was amended with glutamic acid at a rate of 250 mg N/kg and placed under waterlogged incubation. The possibility that the acidic pH of the subsoil, or the lack of a significant subsoil microbial population, was inhibiting mineralisation was also examined by increasing soil pH from 4.4 to 7.0, and inoculating the subsoil with surface soil microorganisms during waterlogged incubations. Low concentrations of N, approximately 90 kg N/ha between 1.2 and 3 m, were found in the native vegetation root material. In addition, no net N mineralisation was observed in either the extended incubation of intact cores or in the control samples of the waterlogged incubations. Net N mineralisation was also not detected when the subsoil was amended with a source of organic N. Results indicate that this lack of mineralisation is largely due to pH inhibition of the microbial population. It is concluded that the mineralisation of either in situ organic material, or DON transported to the subsoil during leaching events, is unlikely to have significantly contributed to the subsoil NH4 accumulation at the study site.
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Hall, Trevor J., John G. McIvor, Paul Jones, David R. Smith, and David G. Mayer. "Comparison of stocking methods for beef production in northern Australia: seasonal diet quality and composition." Rangeland Journal 38, no. 6 (2016): 553. http://dx.doi.org/10.1071/rj15122.
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Managing and measuring the grazing and nutrition of cattle are required to improve the productivity and profitability of beef businesses in northern Australia. The quality and composition of the diet selected by cattle grazing in three stocking methods (continuous, extensive rotation and intensive (cell) rotation) on nine commercial properties in Queensland were estimated using near infrared reflectance spectroscopy analyses of fresh faeces; 585 faecal samples were analysed between 2005 and 2009. Sites were in two regions (north and south Queensland) and on two vegetation communities, namely brigalow (Acacia harpophylla F. Muell. ex Benth.) on clay soils and eucalypts on light-textured soil types. Pastures were dominated by perennial sown exotic grass species, predominantly Cenchrus ciliaris L. (buffel grass) at five sites and Urochloa mosambicensis (Hack.) (Sabi grass) at one site, and by native perennial tussock grasses at three sites. Seasonal profiles of dietary crude protein, dry matter digestibility, faecal nitrogen concentration, proportion of non-grass, ratio of crude protein to digestibility and an estimate of liveweight gain are presented for each stocking method. Overall, dietary crude protein, digestibility, faecal nitrogen, the crude protein : digestibility ratio and liveweight gain were significantly higher for animals grazed continuously, with short rest periods, than for animals in extensive or intensive rotations. There was a significant interaction between stocking method and pasture growing conditions, measured as a simulated growth index, for dietary crude protein and faecal nitrogen. There was no difference between stocking methods during periods when the index was <0.2, indicating no pasture growth, but during periods of active growth (index >0.5), crude protein and faecal nitrogen were higher with continuous grazing than in the extensive and intensive rotations. For cattle producers considering alternative stocking methods, the results suggest they can obtain similar ecological responses under any of the three methods and diet quality will be higher during the pasture growing period in continuously grazed pastures.
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Dalal, R. C., B. A. Cowie, D. E. Allen, and S. A. Yo. "Assessing carbon lability of particulate organic matter from δ13C changes following land-use change from C3 native vegetation to C4 pasture." Soil Research 49, no. 1 (2011): 98. http://dx.doi.org/10.1071/sr10083.
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Land-use change from C3 vegetation (δ13C values, –30‰ to –24‰) to C4 vegetation (δ13C values, –14‰ to –11‰) provides a useful quantitative technique for estimating organic C turnover in soil, even when total organic C changes are negligible. We utilised this technique to estimate C turnover in physically fractionated soil organic matter, particulate organic matter C (POM C >250 μm fraction and POM C 250–53 μm fraction), and the <53 μm fraction. There were small changes in total soil organic C (SOC) after 23 years of land-use change from native vegetation (mixed vegetation of Acacia harpophylla and Casuarina cristata) to buffel grass (Cenchrus ciliaris L. cv. Biloela) pasture grown on Vertosol–Dermosol–Sodosol soil types. The SOC values (t/ha) under native vegetation were: 31 ± 3 for the 0–0.1 m depth, 21 ± 1 for the 0.1–0.2 m depth, 15 ± 3 for the 0.2–0.3 m depth, and 16 ± 2 for the 0.3–0.4 m depth; the corresponding SOC values under pasture were 25 ± 2, 19 ± 2, 14 ± 2, and 13 ± 1 t/ha. The respective δ13C values in 0–0.1 m depths of the whole SOC and POM C >250 μm fraction changed from –25.5 ± 0.1‰ and –25.5 ± 0.3‰ under native vegetation to –20.1 ± 0.5‰ and –19.4 ± 0.2‰ under pasture. Similar, although smaller, differences were observed for other depths and SOC fractions. The SOC turnover periods (years) were 31 ± 6 for the 0–0.1 m depth, 60 ± 5 for the 0.1–0.2 m depth, 55 ± 15 for the 0.2–0.3 m depth, and 63 ± 20 for the 0.3–0.4 m depth; the corresponding turnover periods for the POM C >250 μm fraction were 13 ± 2, 19 ± 5, 14 ± 4, and 12 ± 5 years. The turnover periods of SOC in the POM C 250–53 μm and <53 μm fractions were similar to, or longer than, for the whole SOC at all depths studied. Thus, the lability of the SOC and SOC pools was in the order: POM C >250 μm fraction > POM C 53–250 μm fraction = POM C <53 μm fraction = whole SOC.
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Leach, GJ, and HF Recher. "Use of roadside remnants of softwood scrub vegetation by birds in south-eastern Queensland." Wildlife Research 20, no. 2 (1993): 233. http://dx.doi.org/10.1071/wr9930233.
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Birds in roadside and remnant patches of vegetation in the Marburg district of south-eastern Queensland were studied from November 1989 to February 1990. Effects of the length, width and height of the tree, shrub and herb layers, and their major components, on the bird community were determined. In all, 43 species of birds were observed in roadside vegetation; 16 of these were abundant and widely distributed. Silvereyes were most frequently observed (240 observations), followed by superb fairy-wrens (59), yellow thornbills (53), double-barred finches (26), red-backed fairy-wrens (25) and Lewin's honeyeaters (20). Apart from silvereyes (20-654 of observations), and superb fairy-wrens on two roads (12 and 13%) and yellow thornbills on one (15%), no other species constituted more than 10% of observations on any road. In all, 48 species of birds were observed in remnant patches of vegetation, 14 in all of them. Rates of detection in remnant patches ranged from 2.7 to 5.3 birds per 5 min compared with a mean maximum rate for roadside vegetation of 1.3. The richness of the roadside avifauna increased significantly (P=0.001) as the volume (length x width x height) of the tree component, especially the softwood species, increased. The diversity of tree species in softwood remnants and the greater canopy density appear to be important factors that enhance the bird community. The number of birds was also correlated (P=0.05) with the volume of brigalow, Acacia harpophylla. The correlation of the volume of woody weeddshrubs with the number of birds was low (P=0.05), and with the number of species not significant, even though woody weeds were a major component of roadside vegetation. Although supporting fewer birds than remnant patches of vegetation, roadside vegetation contributes importantly to conservation of the avifauna in the Marburg district. Some simple management practices, such as maintaining a minimum width of undisturbed vegetation and retaining vegetation diversity, would ensure or enhance the long-term conservation benefits. Opportunities to regenerate softwood remnants could also be taken, particularly to enhance the value, and possibly prolong the life, of the associated remnants of brigalow.
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Skjemstad, J. O., L. R. Spouncer, B. Cowie, and R. S. Swift. "Calibration of the Rothamsted organic carbon turnover model (RothC ver. 26.3), using measurable soil organic carbon pools." Soil Research 42, no. 1 (2004): 79. http://dx.doi.org/10.1071/sr03013.
Full textAbstract:
A fractionation scheme that provided the measurement of a labile pool (particulate organic carbon), a charcoal-carbon pool, and a humic pool by difference was tested as a means of initialising the Rothamsted organic carbon turnover model version 26.3. Equating these 3 fractions with the resistant plant material, inert organic matter, and humic pools of the model, respectively, gave good agreement between measured and modelled data for 2 long-term rotation trials in Australia using a soil depth of 30 cm. At one location, Brigalow Research Station in Queensland, there were 3 distinct soil types, two clays and a duplex soil, in a semi-arid, subtropical climate. At this site, continuous wheat with some sorghum was established after clearing land under brigalow (Acacia harpophylla) and continued for 18 years. The second location was near Tarlee, South Australia, and was established on existing agricultural land. One soil type (red brown earth) with 2 rotations (continuous wheat and wheat–fallow) were available over a period of 8 years.The modelled and measured data were in good agreement for both locations but the level of agreement was substantially improved when the resistant plant material decomposition rate was reduced from 0.3 to 0.15/year. No other modifications were required and the resulting values provided excellent agreement between the modelled and measured data not only for the total soil organic carbon but also for the individual pools. Using this fractionation scheme therefore provides an excellent means of initialising and testing the Rothamsted model, not only in Australia, but also in countries with similar soil types and climate.For the first time, the work reported here demonstrates a methodology linking measured soil carbon pools with a conceptual soil carbon turnover model. This approach has the advantage of allowing the model to be initialised at any point in the landscape without the necessity for historical data or for using the model itself to generate an initial equilibrium pool structure. The correct prediction of the changing total soil organic carbon levels, as well as the pool structure over time, acts as an internal verification and gives confidence that the model is performing as intended.
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Skjemstad, JO, VR Catchpoole, and RP Lefeuvre. "Carbon dynamics in vertisols under several crops as assessed by natural abundance 13C." Soil Research 32, no. 2 (1994): 311. http://dx.doi.org/10.1071/sr9940311.
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The effects of three annual crops (oats, C3, Avena sativa; sorghum, C4, Sorghum bicolor; black gram, C3, Vigna mungo) and a grass pasture (green panic, C4, Panicum maximum) on the content and turnover of organic carbon (0-0.15 m) in Vertisols in south-eastern Queensland were measured. Monocultures of the crops and pasture were grown for 11 years in two blocks (1 and 3) established by cultivating a 44 year old C4 Rhodes grass (Chloris gayana) pasture. The site was previously under C3 brigalow (Acacia harpophylla) scrub. In block 1 on Paleustollic Pellusterts, the organic carbon in both the <1.6 Mg m-3 and the >1.6 Mg m-3 fractions decreased linearly with time in the cultivated plots and increased linearly with time in the green panic pasture. In block 3, the organic carbon content of the light fraction (<1.6 Mg m-3) and the heavy fraction (>1.6 Mg m-3) in the oats and green panic plots on Typic Pellusterts also showed a linear relationship with time, decreasing in the cultivated plots and increasing under pasture. The organic carbon content of the soil fraction >1.6 Mg m-3 from the black gram and sorghum plots on Paleustollic Chromusterts showed an initial rapid decline over 2 years with a subsequent slower linear decline. The proportions of organic carbon in the soil due to the original C3 brigalow forest and the subsequent C4 pasture were calculated from the �13C values of the heavy soil fractions. In block 1, cultivation resulted in a decline in both the C3 and C4 pools. In block 3, cultivation resulted in a more rapid decline in the older C3 pool than the C4 pool. The rate of decline in block 3 was associated with soil type and, upon cultivation, the C3 carbon in the Chromusterts declined more rapidly than that in the Pellusterts. Organic carbon which was part of the resistant pool under pasture therefore contributed significantly to the labile pool on cultivation. There appeared to be major differences in the mechanisms protecting the organic matter from microbial degradation in the different soil types. In the Chromusterts, a proportion of the older C3 pool which may have been physically protected under pasture was rapidly mineralized on cultivation. The mechanisms protecting the C3 pool in the Pellusterts appeared to be more stable to physical disruption and therefore more resistant to degradation.
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Scanlan, J. C. "Some aspects of tree-grass dynamics in Queensland's grazing lands." Rangeland Journal 24, no. 1 (2002): 56. http://dx.doi.org/10.1071/rj02003.
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This review examines the interactions between grasses and trees that are relevant to Queensland's grazing lands. Soils and climate determine the potential amount of woody vegetation within an area and clearing, fire and grazing management can modify that potential. In general, the presence of non-leguminous trees reduces the potential grass production beneath their canopy and within woodland patches. Some non-native leguminous trees (e.g. Indian siris, Albizia lebbeck) enhance production of grasses beneath their canopies, whereas the widespread native leguminous trees, mulga (Acacia aneura) and brigalow (A. harpophylla) have not been reported to enhance grass production in the same way. At the patch scale, pasture production beneath woodlands with moderate to high tree basal areas is generally less than in open patches under the same soil and climatic conditions. At a landscape level, tree density, rainfall amount and distribution, and soil type modify pasture production within forest/woodland/shrubland systems. Grasses can reduce tree seedling survival but have little impact on mature woody plants, apart from providing fuel to carry a fire. Modelling studies have been used to examine some aspects of tree-grass production. Firstly, the relationship between grass production and an increasing amount of trees can vary from linear decrease, to exponential decrease to initial stimulation followed by a decrease, depending solely on the relative strengths of stimulatory and competitive effects of trees on grasses. Secondly, simulated pasture production within woodlands shows that the pasture production may be up to 50% higher in paddocks that have high variability in the distribution of those trees compared with areas where trees are uniformly distributed. This is due to the non-linear (negative exponential) relationship between pasture production and tree density that is commonly observed within Queensland. Lastly, simulation studies show that total aboveground production (trees and pasture) of mulga woodland increases as the number of trees per hectare increases. The pasture production response to tree clearing or tree planting depends on tree species, rainfall, soil type, climatic history and post-clearing management including fire and grazing, and will change with time since clearing. The greatest relative increase in pasture production following the removal of woody vegetation occurs: when the initial tree basal area is highest; where rainfall is evenly distributed though the year and on fertile soils with a low water holding capacity.
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Robertson, F. A., R. J. K. Myers, and P. G. Saffigna. "Nitrogen cycling in brigalow clay soils under pasture and cropping." Soil Research 35, no. 6 (1997): 1323. http://dx.doi.org/10.1071/s97026.
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Clay soils previously under native brigalow (Acacia harpophylla) forest are highly productive under annual cropping in central and southern Queensland. Grass pastures sown on these soils are initially productive, but deteriorate after several years because of N-stress (rundown). The aim of this work was to compare the patterns of N cycling in these pasture and cropping systems, in order to understand the rundown of the pastures. A small pulse of 15N-labelled ammonium sulfate was applied in the field to sites cropped with sorghum (Sorghum bicolor) and under green panic (Panicum maximum var. trichoglume) pasture, and its movement through the soil and plant pools was followed over 2 growing seasons. There were large differences in the cycling of 15N in the cropping and pasture systems. Under sorghum, 60% of the applied 15N was immobilised by microorganisms after 4 days, after which it was re-mineralised. Plant uptake and stabilisation in soil organic matter and clay were relatively slow. The first sorghum crop assimilated 14% of the applied 15N. During the second season, most of the 15N was stabilised in soil organic matter and clay (maximum 42%). A significant proportion of the 15N remained in the soil inorganic pool over the 2 seasons. Under green panic, 82% of the 15N left the soil inorganic pool within 4 days and entered the microbial biomass, soil organic matter, and the plant. Uptake and re-release of 15N were most rapid in the microbial biomass (maximum uptake 34% of applied after 4 days). Microbial immobilisation and re-mineralisation were, however, slower under green panic than under sorghum. The pasture plant accumulated 32% of the applied 15N, two-thirds of which was re-released in the second season. Stabilised N represented up to 62% of the applied 15N, and was consistently greater under green panic than under sorghum. After 2 seasons, 15N was released from the stabilised N pool in both systems, at approximately the same rate as it had been stabilised. At the end of the experiment, 40% of the applied 15N was unaccounted for in the pasture system, and 66% in the crop system. The reduced N availability in the pasture system was attributed to immobilisation of N in soil organic matter and clay, plant material, and, to a lesser extent, soil microbial biomass. This immobilisation resulted from the large accumulation of carbonaceous plant residues.
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Burrows, Geoffrey E., Rowan Alden, and Wayne A. Robinson. "The lens in focus – lens structure in seeds of 51 Australian Acacia species and its implications for imbibition and germination." Australian Journal of Botany 66, no. 5 (2018): 398. http://dx.doi.org/10.1071/bt17239.
Full textAbstract:
Acacia s. str. (Mimosoideae, Fabaceae) is the largest plant genus in Australia (~1000 species). Its seeds have physical dormancy from a hard, water-impermeable testa. Heat from fire (natural systems) and hot water (nursery production) can break this dormancy. It is often reported that these treatments ‘soften’ or ‘crack’ the seed coat, but in practice they only affect a minute part of the seed coat, the lens. We examined lens structure in a wide range of Acacia species to determine what diversity of testa and lens structure was present, if there were differing responses to a hot water dormancy breaking treatment and if there were structural differences between soft- and hard-seeded species. Seed morphology, testa and lens structure were examined before and after hot water treatment (~90°C for one minute), in 51 species of Australian Acacia from all seven sections, from all states and territories of Australia and from a wide range of environments. Five of the species had been noted to produce non-dormant seed (‘soft-seeded’ species). Average seed mass per species ranged from 3.1 to 257.9 mg (overall average 24.2 mg, median 13.8 mg). Almost all species had a relatively thick seed coat (average 132.2 µm) with well-developed palisade cells (average 41.5 µm long) and a lens which ‘popped’ in response to hot water treatment. For 44 species ranging in average seed mass from 3.1 to 43.9 mg (×14 range), the unpopped lens area only ranged ×3 (11480–36040 µm2). The lens was small (in 88% of species the average length of the unpopped lens was <300 µm) and the unpopped lens area was a minute proportion of seed surface area (average 0.10%). A. harpophylla (soft-seeded species) had a thin testa (37.3 µm) without obvious palisade cells and did not have a functional lens. In hard-seeded species the morphology of the popped lens varied widely, from a simple mound to complete detachment. A functional lens is not a universal feature in all genera of the Mimosoideae, including several species in a genus (Senegalia) previously included in Acacia s. lat. On the basis of the 51 investigated species a lens was present in all Australian acacias, although non-functional in two soft-seeded species. Although the lens was, on average, only ~1/1000th of the surface area of an Acacia seed and thus easily overlooked, it can have a profound influence on imbibition and germination. An assessment of lens structure, before and after heat treatment, can be of considerable use when interpreting the results of Acacia germination experiments.
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Bortolussi, G., J. G. McIvor, J. J. Hodgkinson, S. G. Coffey, and C. R. Holmes. "The northern Australian beef industry, a snapshot. 4. Condition and management of natural resources." Australian Journal of Experimental Agriculture 45, no. 9 (2005): 1109. http://dx.doi.org/10.1071/ea03262.
Full textAbstract:
Natural resource management practices were surveyed on 375 northern Australian beef properties in 8 regions during 1996–97. These producers represented a broad cross section of the beef industry in terms of geographical location, size of enterprise, and herd and ownership structures. More than 48% of producers reported land degradation (erosion, salinity, weeds, etc.) and >68% reported woody weeds on their properties. Eucalypt (Eucalyptus and Corymbia spp.) and wattle (Acacia spp.) regrowth were universally common native woody weeds. Parkinsonia (Parkinsonia aculeata) was widespread across all survey regions occurring with the greatest frequency in northern regions. A range of native and exotic woody weed species were regionally significant. Brigalow (Acacia harpophylla) regrowth was mainly reported in the central Queensland and Maranoa South West regions. Prickly acacia (Acacia nilotica) was mainly reported in central and north-west Queensland. Rubber vine (Cryptostegia grandiflora) was mainly reported in northern Queensland with a significant presence in central coastal and north-west Queensland. Infestations with multiple weed species were common. Although many producers reported the presence of problem woody weeds, only 3–29% indicated that weed management was practised. Most producers (67–100%) used fire. The intended purpose of fire varied across survey regions but fire was commonly used to reduce rank material, reduce fire risk, control woody weeds and for grazing management. Seasonal conditions and variability restricted fire use. Assessment by visual observation was a commonly used practice for determining stocking rate. Between 4–20% of producers were using visual observation combined with some form of calculation of stocking rate at the end of the growing season to determine stocking rate. A majority (>67%) of producers used some form of paddock spelling or regeneration practice. Many producers (47–89%) considered that they used conservative stocking rates. Carrying sufficient stock to meet income requirements was significantly (P<0.05) correlated with the percentage of producers reporting woody weeds as a problem on their property. In the 5 years preceding the survey, >66% of producers had increased the number of stock watering points, and more than 85% of producers had erected fencing. Most fencing was for new paddocks and laneways, or to replace old fences, and was not associated with new stock watering points. However, the installation of new stock watering points was associated with the creation of new paddocks. Planned future fencing focused on creating new paddocks or laneways or replacing old fences. The results are discussed in relation to contemporary natural resource management issues and the future approaches to and challenges of implementing sustainable rangeland management.
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Dalal, R. C. "Long-term phosphorus trends in Vertisols under continuous cereal cropping." Soil Research 35, no. 2 (1997): 327. http://dx.doi.org/10.1071/s96052.
Full textAbstract:
Vertisols originally carrying brigalow vegetation (Acacia harpophylla F. Muell. ex Benth.) and cultivated for cereal cropping for up to 45 years were examined for trends in available phosphorus (P) [sodium bicarbonate extractable P (bicarb. P) and dilute acid extractable P (acid P)], organic P, inorganic P, and total P. The soils (0-0 · 1 m depth) in their virgin state contained 60 mg/kg of bicarb. P, 168 mg/kg of acid P, 239 mg/kg of organic P, and 330 mg/kg of inorganic P. All fractions of soil P declined following first-order decay with the period of cereal cropping; the rates of bicarb. P and acid P (available P) decline were 0 · 047 and 0 · 08/year. The organic P, inorganic P, and total P declined more slowly than available P; the respective rates were 0 · 026, 0 · 019, and 0 · 021/year. The rates of loss of total P and inorganic P were much higher from the clay-size fraction than the silt-size or sand-size fraction, with the t½ value of inorganic P in the sand-size fraction being almost 20 times greater than any other fraction. On the other hand, organic P loss from the clay-size fraction was much less; presumably, clay provides physical protection to soil organic matter and hence to organic P from decomposition. On average, bicarb. P and acid P declined at the rate of 1 · 3±0 · 3 and 4 · 6±1 · 4 mg P/kg soil · year. The declines in organic P and inorganic P were 3 · 0±0.4 and 4 · 1±1 · 2 mg P/kg soil · year, with a loss in total P of 7 · 2±1 · 3 mg P/kg soil · year. There was no significant shift in the ratio organic P: total P (38±7%) with the period of cultivation and cereal cropping. Organic P was closely correlated with organic C and total N in these soils. The mean amounts of P contained in the grain and the dry matter of each cereal crop from 1981 and 1984 were 7 · 6±1 · 8 and 8 · 3±2 · 4 kg P/ha, respectively. Thus, most of the soil total P loss could be accounted for by crop removal, of which organic P contributed about 40%. However, the continuous decline in available P, especially below 15 mg P/kg soil, warrants remedial measures to arrest the decline in the yields of crops grown on these Vertisols.
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Mound, LA, BJ Crespi, and B. Kranz. "Gall-Inducing Thysanoptera (Phlaeothripidae) on Acacia Phyllodes in Australia: Host-plant relations and keys to genera and species." Invertebrate Systematics 10, no. 6 (1996): 1171. http://dx.doi.org/10.1071/it9961171.
Full textAbstract:
The available biological information on the association, unique to Australia, between gall-inducing thrips and the phyllodes of Acacia species is summarised. Identification keys to the three genera and 21 gall-inducing species involved are presented, together with descriptions of nine new species (Kladothrips harpophyllae, Kladothrips maslini, Kladothrips xiphius, Oncothrips morrisi, Oncothrips schwarzi, Oncothrips sterni, Oncothrips torus, Onychothrips pilbara and Onychothrips zygus).
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Thornton, C. M., and K. Shrestha. "The Brigalow Catchment Study: V*. Clearing and burning brigalow (Acacia harpophylla) in Queensland, Australia, temporarily increases surface soil fertility prior to nutrient decline under cropping or grazing." Soil Research, 2020. http://dx.doi.org/10.1071/sr20088.
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