Amino acid geochronology of foraminifera test from north Queensland margin

In this study, we demonstrate the utility of amino acid geochronology based on single-foraminiferal tests in Quaternary sediment cores from the Queensland margin, Australia. The large planktonic foraminifer Pulleniatina obliquiloculata is ubiquitous in shelf, slope, and basin sediments of north Queensland as well as pantropical oceans. Fossil tests are resistant to dissolution, and retain substantial concentrations of amino acids (2-4 nmol/mg of shell) over hundreds of thousands of years. Amino acid D and L isomers of aspartic acid (Asp) and glutamic acid (Glu) were separated using reverse phase chromatography, which is sensitive enough to analyze individual foraminifera tests. In all, 462 Pulleniatina tests from 80 horizons in 11 cores exhibit a systematic increase in D/L ratios down core. D/L ratios were determined in 32 samples whose ages are known from AMS 14C analyses. In all cases, the Asp and Glu D/L ratios are concordant with 14C age. D/L ratios of equal-age samples are slightly lower for cores taken from deeper water sites, reflecting the sensitivity of the rate of racemization to bottom water temperature. Beyond the range of 14C dating, previously identified marine oxygen-isotope stage boundaries provide approximate ages of the sediments up to about 500,000 years. For this longer time frame, D/L ratios also vary systematically with isotope-correlated ages. The rate of racemization for Glu and Asp was modeled using power functions. These equations can be used to estimate ages of samples from the Queensland margin extending back at least 500,000 years. This analytical approach provides new opportunities for geochronological control necessary to understand fundamental sedimentary processes affecting a wide range of marine environments.

Composite of coastal seagrass meadows in Queensland, Australia - November 1984 to June 2010

Approximately 18,400 km**2 of seagrass habitat has been mapped within the coastal waters (<15 m) of Queensland (Australia) between November 1984 and June 2010. The total seagrass meadow distribution was calculated by merging maps from 115 separate mapping surveys (varying locations and dates). Due to tropical seagrass dynamism, meadow distribution can change seasonally and between years, and as a consequence, the composite represents the maximum area of seabed where seagrass has been observed/recorded. Mapping survey methodologies followed standardised global seagrass research methods (McKenzie et al. 2001) where the presence of seagrass was determined from in situ visual assessment of the seabed by either divers or drop cameras at GPS marked positions. Seagrass meadow boundaries were determined based on the positions of survey sites and the presence of seagrass, coupled with depth contours and remote sensing (e.g. aerial photography) where available. The merged meadow boundary accuracy was dependent on the original survey maps and varied from 10-100 m. The resulting composite seagrass distribution was saved as an ArcMap polygon shapefile, and projected to Geocentric Datum of Australia GDA94.

Middle Miocene mineralogical events of Marion Plateau, northeast of Australia

Three ODP sites located on the Marion Plateau, Northeast Australian margin, were investigated for clay mineral and bulk mineralogy changes through the early to middle Miocene. Kaolinite to smectite (K/S) ratios, as well as mass accumulation rates of clays, point to a marked decrease in accumulation of smectite associated with an increase in accumulation of kaolinite starting at ~15.6 Ma, followed by a second increase in accumulation of kaolinite at ~13.2 Ma. Both of these increases are correlative to an increase in the calcite to detritus ratio. Comparison of our record with published precipitation proxies from continental Queensland indicates that increases in kaolinite did not correspond to more intense tropical-humid conditions, but instead to periods of greater aridity. Three mechanisms are explored to explain the temporal trends in clay on the Marion Plateau: sea-level changes, changes in oceanic currents, and denudation of the Australian continent followed by reworking and eolian transport of clays. Though low mass accumulation rates of kaolinite are compatible with a possible contribution of eolian material after 14 Ma, when Australia became more arid, the lateral distribution of kaolinite along slope indicates mainly fluvial input for all clays and thus rules out this mechanism as well as oceanic current transport as the main controls behind clay accumulation on the plateau. We propose a model explaining the good correlation between long-term sea-level fall, decrease in smectite accumulation, increase in kaolinite accumulation and increase in carbonate input to the distal slope locations. We hypothesize that during low sea level and thus periods of drier continental climate in Queensland, early Miocene kaolinite-rich lacustrine deposits were being reworked, and that the progradation of the heterozoan carbonate platforms towards the basin center favored input of carbonate to the distal slope sites. The major find of our study is that increase kaolinite fluxes on the Queensland margin during the early and middle Miocene did not reflect the establishment of a tropical climate, and this stresses that care must be taken when reconstructing Australian climate based on deep-sea clay records alone.

Stem and crown dimensions as predictors of thinning responses in a crowded tropical rainforest plantation of Flindersia brayleyana F. Muell.

A 67-year-old plantation of Flindersia brayleyana F. Muell. in the wet tropics of north-cast Queensland had developed with minimal management. Before thinning, the stand had a canopy stem density of 770 stems ha(-1) of which 564 were F brayleyana, a stand basal area of 78 m(2) ha(-1), a mean stem diameter at breast height (dbh) of 36 cm, and a mean dbh increment of 5.2 mm year(-1) over the life of the plantation and 0.5 mm year I at the time of thinning. Sixty-three percent of the trees had crown ratios (crown diameter determined from foliage projected area: dbh) of less than 12. Thinning treatments removed 57% of the canopy stems and 45% of the stand basal area. Mean dbh increment over 2.5 years after thinning on basaltic soil was 5.8 +/- 0.3 mm year(-1), but for trees with crown ratio

Selection of species and provenances for low-rainfall areas: physiological responses of Eucalyptus cloeziana and Eucalyptus argophloia to seasonal conditions in subtropical Queensland

Responses of stomatal conductance (g(s)) and net photosynthesis (A) to changes in soil water availability, photosynthetic photon flux density (Q), air temperature (1) and leaf-to-air vapour pressure deficit (D) were investigated in 4-year-old trees of a dry inland provenance of Eucalyptus argophloia Blakely, and two dry inland provenances (Coominglah and Hungry Hills) and a humid coastal provenance (Wolvi) of Eucalyptus cloeziana F. Muell. between April 2001 and April 2002 in southeast Queensland, Australia. There were minimal differences in A, g, and water relations variables among the coastal and inland provenances of E. cloeziana but large differences between E. argophloia and E. cloeziana. E. argophloia and to a lesser extent the Hungry Hills (inland) provenance of E. cloeziana maintained relatively higher pre-dawn water potential (psi(pd)) during the dry season suggesting possible access to water at depth. Simple phenomenological models of stomatal conductance as a function of Q, T and D explained 60% of variation in gs in E. cloeziana and more than 75% in E. argophloia, when seasonal effect was incorporated in the model. A Ball-Berry model for net photosynthesis explained between 70 and 80% of observed variation in A in both species. These results have implications in matching the dry and humid provenances of E. cloeziana and E. argophloia to suitable sites in subtropical environments. (C) 2004 Elsevier B.V. All rights reserved.

Pollen transport and deposition in riverine and marine environments within the humid tropics of northeastern Australia

Mechanisms of pollen transport in the humid tropics region of northeastern Australia were investigated to support the interpretation of a long Quaternary pollen record from ODP Site 820 located on the adjacent continental slope. Pollen analysis of surface sediment samples from the channels of two major river catchments demonstrated internal consistency in pollen spectra and little fluvial pollen sorting in relation to sediment variation. Differences in modem pollen spectra between catchments reflect existing variation in vegetation cover that, in turn, reflects climatic differences between catchments. Recent pollen spectra from top samples of the ODP core have sufficient in common with the riverine samples to suggest that the rivers are contributing a major pollen component to the offshore sediments, but these have been size sorted by marine action. Recent pollen samples from core tops taken from the Grafton Passage on the continental shelf that was thought to be the major passage for pollen transport to ODP Site 820 show significant differences to both riverine and ODP samples and suggest that pollen are dispersed across the continental shelf and through the outer Great Barrier Reef system in a more complex way than anticipated. (c) 2004 Elsevier B.V. All rights reserved.

Potential economic implications for regional tourism of a Foot and Mouth Disease outbreak in North Queensland

International and domestic tourism are sensitive to disastrous events which make areas inaccessible to visitors, less attractive or more dangerous. One form of tourism disaster is the outbreak of an exotic disease, of which Foot and Mouth Disease (FMD) is a prime case. It is now well documented that the 2001 FMD outbreak in the UK had a greater impact on tourism than on agriculture. It has been estimated than an FMD outbreak in Australia would impose a cost of about $13 million. The impact on tourism would be highly dependent on the extent and duration of an FMD outbreak, as well as on any management and containment restrictions imposed by the authorities in their attempt to control and eventually eradicate the disease. Public perception and thus the provision of accurate information and the way in which the media report disasters will also play an important role in determining the impact on the tourism industry. The economy of Tropical North Queensland relies heavily on international visitors, and an FMD outbreak in the region would impose a large cost to the regional economy, conservatively estimated here to be of the order of $200 million per year.

A new estimate for the composition of weathered young upper continental crust from alluvial sediments, Queensland, Australia

We present new major element, trace element and Nd-isotope data for 30 alluvial sediments collected from 25 rivers in Queensland, E Australia. Samples were chosen to represent drainage from the region's most important lithologies, including Tertiary intraplate volcanic rocks, a Cretaceous igneous province (and sedimentary rocks derived thereof) as well as Proterozoic blocks. In most chemical and isotopic aspects, the alluvial sediments represent binary or ternary mixing relationships, with absolute abundances implied to reflect the proportion of lithologies in the catchments. When averaged, the studied sediments differ from other proxies of upper continental crust (UCC) mainly in their relative middle rare earth element enrichment (including an elevated Sm/Nd ratio), higher relative Eu abundance and higher Nb/Ta ratio. These features are inherited from eroded Tertiary intraplate basalts, which commonly form topographic highs in the studied region. Despite the high degree of weathering strong to excellent coherence between similarly incompatible elements is found for all samples. From this coherence, we suggest revisions of the following upper crustal element ratios: Y/Ho = 26.2, Yb/Tm = 6.37, Th/W = 7.14, Th/Tl = 24 and Zr/Hf = 36.9. Lithium, Rb, Cs and Be contents do not seem depleted relative to UCC, which may reflect paucity of K-feldspar in the eroded catchments. Nickel, Cr, Pb, Cu and Zn concentrations are elevated in polluted rivers surrounding the state capital. River sediments in the Proterozoic Georgetown Inlier are elevated in Pb, Cu and Zn but this could be a natural phenomenon reflecting abundant sulphide mineralisation in the area. Except for relative Sr concentrations, which broadly anticorrelate with mean annual rainfall in catchments, there is no obvious relationship between the extent of weathering and climate types, which range from and to tropical. The most likely explanation for this observation is that the weathering profiles in many catchments are several Myr old, established during the much wetter Miocene period. The studied sediment compositions (excluding those from the Proterozoic catchments) are used to propose a new trace element normalisation termed MUQ (MUd from Queensland), which serves as an alternative to UCC proxies derived from sedimentary rocks. Copyright (C) 2005 Elsevier Ltd

Prevalence, severity, and heritability of Stephanofilaria lesions on cattle in central and southern Queensland, Australia

Observations of cattle in central and southern Queensland are collated to de. ne the prevalence and area of Stephanofilaria lesions associated with infestations of the buffalo fly, Haematobia irritans exigua. The observations were made on herds that were being used for other purposes. In a survey of similar to 1500 animals at Belmont in central Queensland in 1982, 98% of cows and 70% of calves had lesions. Most lesions were on the neck and dewlap and 10% were raw and weeping at the time of sampling. The total area of lesions per animal was strongly related to cattle breed and age. Old Bos taurus animals had the greatest area of lesions, whereas young Bos indicus had the least. Heritability estimates were low, averaging 0.01 for calves and 0.18 for cows. A smaller survey of cows and steers at Craighoyle in central Queensland in 1986 showed a higher numbers of lesions and positive correlations between the total lesion area and animal size. The lesion area increased with tick survival, suggesting that tick-resistant animals are also resistant to Stephanofilaria infection. Steers had smaller areas of lesions than cows, as found previously with cattle ticks. Long-term monitoring observations in central and southern Queensland between 1981 and 1986 showed that the total area of lesions was seasonal with a peak in late summer, consistent with the seasonal incidence of buffalo fly. Animals segregated into Low and High lesion herds maintained their differences over time. The lesions penetrated the dermis of the cattle hides and rendered the affected area unusable, but few lesions occurred on valuable parts of the hide so such economic effects are likely to be insignificant. One animal nearly died of a haemorrhage from a lesion on the dewlap and had to be treated. The results can inform policy on buffalo fly control, and biosecurity preparations in relation to the potential establishment of the OldWorld screw-worm fly, Chrysomyia bezziana, in Australia, which will be facilitated by the lesions. The results emphasise the significant animal welfare and biosecurity risks posed by the lesions in northern Australia.

Tree species diversity and ecosystem function: Can tropical multi-species plantations generate greater productivity?

Results from the humid tropics of Australia demonstrate that diverse plantations can achieve greater productivity than monocultures. We found that increases in both the observed species number and the effective species richness were significantly related to increased levels of productivity as measured by stand basal area or mean individual tree basal area. Four of five plantation species were more productive in mixtures with other species than in monocultures, offering on average, a 55% increase in mean tree basal area. A general linear model suggests that species richness had a significant effect on mean individual tree basal area when environmental variables were included in the model. As monoculture plantations are currently the preferred reforestation method throughout the tropics these results suggest that significant productivity and ecological gains could be made if multi-species plantations are more broadly pursued. (c) 2006 Elsevier B.V. All rights reserved.

The availability of nitrogen from sugarcane trash on contrasting soils in the wet tropics of North Queensland

Sugarcane crop residues ('trash') have the potential to supply nitrogen (N) to crops when they are retained on the soil surface after harvest. Farmers should account for the contribution of this N to crop requirements in order to avoid over-fertilisation. In very wet tropical locations, the climate may increase the rate of trash decomposition as well as the amount of N lost from the soil-plant system due to leaching or denitrification. A field experiment was conducted on Hydrosol and Ferrosol soils in the wet tropics of northern Australia using N-15-labelled trash either applied to the soil surface or incorporated. Labelled urea fertiliser was also applied with unlabelled surface trash. The objective of the experiment was to investigate the contribution of trash to crop N nutrition in wet tropical climates, the timing of N mineralisation from trash, and the retention of trash N in contrasting soils. Less than 6% of the N in trash was recovered in the first crop and the recovery was not affected by trash incorporation. Around 6% of the N in fertiliser was also recovered in the first crop, which was less than previously measured in temperate areas (20-40%). Leaf samples taken at the end of the second crop contined 2-3% of N from trash and fertilizer applied at the beginning of the experiment. Although most N was recovered in the 0-1.5 m soil layer there was some evidence of movement of N below this depth. The results showed that trash supplies N slowly and in small amounts to the succeeding crop in wet tropics sugarcane growing areas regardless of trash placement (on the soil surface or incorporated) or soil type, and so N mineralisation from a single trash blanket is not important for sugarcane production in the wet tropics.

Cattle, crops and clearing: Regional drivers of landscape change in the Brigalow Belt, Queensland, Australia, 1840-2004

Landscape change occurs through the interaction of a multitude of natural and human driving forces at a range of organisational levels, with humans playing an increasingly dominant role in many regions of the world. Building on the current knowledge of the underlying drivers of landscape change, a conceptual framework of regional landscape change was developed which integrated population, economic and cultural values, policy and science/technology. Using the Southern Brigalow Belt biogeographic region of Queensland as a case study, the role of natural and human drivers in landscape change was investigated in four phases of settlement since 1840. The Brigalow Belt has experienced comparable rates of vegetation clearance over the past 50 years to areas of tropical deforestation. Economic factors were important during all phases of development, but the five regional drivers often acted in synergy. Environmental constraints played a significant role in slowing rates of change. Temporal trends of deforestation followed a sigmoidal curve, with initial slow change accelerating though the middle phases then slowing in recent times. Future landscape management needs to take account of the influence of all the components of the conceptual framework, at a range of organisational levels, if more ecologically sustainable outcomes are to be achieved. (c) 2006 Elsevier B.V. All rights reserved.

Mapping structural parameters and species composition of riparian vegetation using IKONOS and Landsat ETM+ data in Australian tropical savannahs

Government agencies responsible for riparian environments are assessing the utility of remote sensing for mapping and monitoring vegetation structural parameters. The objective of this work was to evaluate Ikonos and Landsat-7 ETM+ imagery for mapping structural parameters and species composition of riparian vegetation in Australian tropical savannahs for a section of Keelbottom Creek, Queensland, Australia. Vegetation indices and image texture from Ikonos data were used for estimating leaf area index (R-2 = 0.13) and canopy percentage foliage cover (R-2 = 0.86). Pan-sharpened Ikonos data were used to map riparian species composition (overall accuracy = 55 percent) and riparian zone width (accuracy within +/- 3 m). Tree crowns could not be automatically delineated due to the lack of contrast between canopies and adjacent grass cover. The ETM+ imagery was suited for mapping the extent of riparian zones. Results presented demonstrate the capabilities of high and moderate spatial resolution imagery for mapping properties of riparian zones.