Determination of specific leaf area of some commercially useful sub-tropical hardwood species

Variability of specific leaf area (SLA) across taxa, sites and crown zones was determined for four sub-tropical hardwood species, Eucalyptus grandis, E. cloeziana, E. argophloia and Corymbia citriodora ssp. variegata, growing in south-eastern Queensland. Mean SLA values were stable amongst those taxa sampled on dry sites but varied markedly between provenances of E. grandis on a moist site. Mean SLA did not vary significantly with crown zone in any of these four sub-tropical eucalypts, which is in contrast to that observed in temperate species, both in Australia and overseas. A provenance of E. cloeziana from a moist coastal site exhibited the largest SLA of all taxa studied.

Effects of fishing on tropical reef associated shark populations on the Great Barrier Reef

Three data sets were examined to define the level of interaction of reef associated sharks with the commercial Coral Reef Fin Fish Fishery within the Great Barrier Reef (GBR). Data were examined from fishery logbooks, an observer program within the fishery and a fishery-independent survey conducted as part of the Effects of Line Fishing (ELF) Experiment. The majority of the identified catch was comprised of grey reef (62-72%), whitetip reef (16-29%) and blacktip reef (6-13%) sharks. Logbook data revealed spatially and temporally variable landings of shark from the GBR. Catch per unit effort (CPUE) through time was stable for the period from 1989 to 2006 with no evidence of increase or decline. Data from observer and ELF data sets indicated no differences in CPUE among regions. The ELF data set demonstrated that CPUE was higher in Marine National Park zones (no fishing) when compared to General Use zones (open to fishing). The ongoing and consistent catches of reef sharks in the fishery and effectiveness of no-fishing zones suggest that management zones within the GBR Marine Park are effective at protecting a portion of the reef shark population from exploitation.

Modelling predicts positive and negative interactions between three Australian tropical tree species in monoculture and binary mixture

Computer modelling promises to be an important tool for analysing and predicting interactions between trees within mixed species forest plantations. This study explored the use of an individual-based mechanistic model as a predictive tool for designing mixed species plantations of Australian tropical trees. The `spatially explicit individually based-forest simulator' (SeXI-FS) modelling system was used to describe the spatial interaction of individual tree crowns within a binary mixed-species experiment. The three-dimensional model was developed and verified with field data from three forest tree species grown in tropical Australia. The model predicted the interactions within monocultures and binary mixtures of Flindersia brayleyana, Eucalyptus pellita and Elaeocarpus grandis, accounting for an average of 42% of the growth variation exhibited by species in different treatments. The model requires only structural dimensions and shade tolerance as species parameters. By modelling interactions in existing tree mixtures, the model predicted both increases and reductions in the growth of mixtures (up to +/-50% of stem volume at 7 years) compared to monocultures. This modelling approach may be useful for designing mixed tree plantations.

Tree-ring based hydroclimate reconstruction over northern Vietnam from Fokienia hodginsii: eighteenth century mega-drought and tropical Pacific influence

We present here the first statistically calibrated and verified tree-ring reconstruction of climate from continental Southeast Asia.The reconstructed variable is March-May (MAM) Palmer Drought Severity Index (PDSI) based on ring widths from 22 trees (42 radial cores) of rare and long-lived conifer, Fokienia hodginsii (Po Mu as locally called) from northern Vietnam. This is the first published tree ring chronology from Vietnam as well as the first for this species. Spanning 535 years, this is the longest cross-dated tree-ring series yet produced from continental Southeast Asia. Response analysis revealed that the annual growth of Fokienia at this site was mostly governed by soil moisture in the pre-monsoon season. The reconstruction passed the calibration-verification tests commonly used in dendroclimatology, and revealed two prominent periods of drought in the mid-eighteenth and late-nineteenth enturies. The former lasted nearly 30 years and was concurrent with a similar drought over northwestern Thailand inferred from teak rings, suggesting a ``mega-drought'' extending across Indochina in the eighteenth century. Both of our reconstructed droughts are consistent with the periods of warm sea surface temperature (SST)anomalies in the tropical Pacific. Spatial correlation analyses with global SST indicated that ENSO-like anomalies might play a role in modulating droughts over the region, with El Nio (warm) phases resulting in reduced rainfall. However, significant correlation was also seen with SST over the Indian Ocean and the north Pacific,suggesting that ENSO is not the only factor affecting the climate of the area. Spectral analyses revealed significant peaks in the range of 53.9-78.8 years as well as in the ENSO-variability range of 2.0 to 3.2 years.

Heritability estimates for growth in the tropical abalone Haliotis asinina using microsatellites to assign parentage

The tropical abalone Haliotis asinina is a wild-caught and cultured species throughout the Indo-Pacific as well as being an emerging model species for the study of haliotids. H. asinina has the fastest recorded natural growth rate of any abalone and reaches sexual maturity within one year. As such, it is a suitable abalone species for selective breeding for commercially important traits such as rapid growth. Estimating the amount of variation in size that is attributable to heritable genetic differences can assist the development of such a selective breeding program. Here we estimated heritability for growth-related traits at 12 months of age by creating a single cohort of 84 families in a full-factorial mating design consisting of 14 sires and 6 dams. Of 500 progeny sampled, 465 were successfully assigned to their parents based on shared alleles at 5 polymorphic microsatellite loci. Using an animal model, heritability estimates were 0.48 ± 0.15 for shell length, 0.38 ± 0.13 for shell width and 0.36 ± 0.13 for weight. Genetic correlations were > 0.98 between shell parameters and weight, indicating that breeding for weight gains could be successfully achieved by selecting for shell length.

Successful management of colletotrichum crown and stolon rot in runner production in sub-tropical Australia

Crown, stolon, and petiole rots caused by Colletotrichum gloeosporioides (C.g.) were first identified in runner beds of the Queensland Approved Runner Scheme (QARS) in February 1989. The outbreaks occurred annually from 1990 to 1994. Minor losses in subsequent fruit crops occurred from 1990 to 1993, with 50% post-establishment losses occurring on fruit farms in southeast Queensland in 1994. The objective of this work was to provide a control strategy for the disease that would give stability to the QARS. Runner-bed trials in 1993-1994 showed that Octave® (462 g/kg prochloraz as the MnCl2 complex) was highly effective in reducing the incidence field symptoms and laboratory recovery of C.g. from symptomless petioles. A simple detached petiole laboratory test for measuring fungicide efficacy in runner bed trials and for laboratory screening of fungicides, is described. Scheme protocols were changed to require that only foundation plants from tissue culture were allowed onto QARS sites. These were to be symptomless and to have tested negative for the presence of C.g. The application of Octave® at fortnightly intervals in all QARS nurseries has reduced the level of visible symptoms and the laboratory recovery of C.g. from symptomless petioles to almost zero.

Ruminal protein degradability of a range of tropical pastures

The rumen degradability parameters of the diet selected by two to four oesophageal-fistulated Brahman steers grazing a range of tropical pastures were determined by incubation of extrusa in nylon bags suspended in the rumen of rumen-fistulated (RF) Brahman steers. The effective protein degradability (Edg) was determined by measuring the rate of disappearance of neutral detergent insoluble nitrogen (NDIN) less acid detergent insoluble nitrogen (ADIN) in the incubated extrusa. Six to eight RF steers also grazed each of the pastures along with the oesophageal-fistulated steers, to allow determination of key rumen parameters and rumen particulate matter fractional outflow rates (FOR). The seven pastures studied included: native tropical grass (C4) pasture (major species Heteropogon contortus and Bothriochloa bladhii), studied in the early wet (NPEW), the wet/dry transition (NPT) and the dry (NPD) seasons; introduced tropical grass (C4) pasture (Bothriochloa insculpta), studied in the mid wet season (BB); the introduced tropical legumes (C3), Lablab purpureus (LL) and Clitoria ternatea (BP); and the temperate grass (C3) pasture, ryegrass (Lolium multiflorum, RG). Using the measured particle FOR values in calculations, the Edg estimates were very high for both C4 and C3 species: 0.82–0.91 and 0.95–0.98 g/g crude protein (CP), respectively. Substitution of an assumed FOR (kp = 0.02/h) for the measured values for each pasture type did not markedly affect estimates of Edg. However, C4 tropical grasses had much lower effective rumen degradable protein (ERDP) fractions (23–66 g/kg DM) than the C3 pasture species RG and LL (356 and 243 g/kg DM, respectively). This was associated with a lower potential degradability and degradation rate of organic matter (OM) in sacco, lower in vitro organic matter digestibility (IVOMD) and CP concentrations in the extrusa, and lower ammonia-N and branched-chain fatty acid concentrations in rumen fluid for the tropical grasses. As tropical grass pastures senesced, there was a decline in Edg, the ERDP and rumen undegradable protein (UDP) fractions, the potential degradability and degradation rate of OM and the IVOMD. These results provide useful data for estimating protein supply to cattle grazing tropical pastures.

Managing for rainfall variability: effect of grazing strategy on cattle production in a dry tropical savanna

Rainfall variability is a challenge to sustainable and pro. table cattle production in northern Australia. Strategies recommended to manage for rainfall variability, like light or variable stocking, are not widely adopted. This is due partly to the perception that sustainability and profitability are incompatible. A large, long-term grazing trial was initiated in 1997 in north Queensland, Australia, to test the effect of different grazing strategies on cattle production. These strategies are: (i) constant light stocking (LSR) at long-term carrying capacity (LTCC); (ii) constant heavy stocking (HSR) at twice LTCC; (iii) rotational wet-season spelling (R/Spell) at 1.5 LTCC; (iv) variable stocking (VAR), with stocking rates adjusted in May based on available pasture; and (v) a Southern Oscillation Index (SOI) variable strategy, with stocking rates adjusted in November, based on available pasture and SOI seasonal forecasts. Animal performance varied markedly over the 10 years for which data is presented, due to pronounced differences in rainfall and pasture availability. Nonetheless, lighter stocking at or about LTCC consistently gave the best individual liveweight gain (LWG), condition score and skeletal growth; mean LWG per annum was thus highest in the LSR (113 kg), intermediate in the R/Spell (104 kg) and lowest in the HSR(86 kg). MeanLWGwas 106 kg in the VAR and 103 kg in the SOI but, in all years, the relative performance of these strategies was dependent upon the stocking rate applied. After 2 years on the trial, steers from lightly stocked strategies were 60-100 kg heavier and received appreciable carcass price premiums at the meatworks compared to those under heavy stocking. In contrast, LWG per unit area was greatest at stocking rates of about twice LTCC; mean LWG/ha was thus greatest in the HSR (21 kg/ha), but this strategy required drought feeding in four of the 10 years and was unsustainable. Although LWG/ha was lower in the LSR (mean 14 kg/ha), or in strategies that reduced stocking rates in dry years like the VAR(mean 18 kg/ha) and SOI (mean 17 kg/ha), these strategies did not require drought feeding and appeared sustainable. The R/Spell strategy (mean 16 kg/ha) was compromised by an ill-timed fire, but also performed satisfactorily. The present results provide important evidence challenging the assumption that sustainable management in a variable environment is unprofitable. Further research is required to fully quantify the long-term effects of these strategies on land condition and profitability and to extrapolate the results to breeder performance at the property level.

Development of near infrared analysis of faeces to estimate non-grass proportions in diets selected by cattle grazing tropical pastures

Grass (monocots) and non-grass (dicots) proportions in ruminant diets are important nutritionally because the non-grasses are usually higher in nutritive value, particularly protein, than the grasses, especially in tropical pastures. For ruminants grazing tropical pastures where the grasses are C-4 species and most non-grasses are C-3 species, the ratio of C-13/C-12 in diet and faeces, measured as delta C-13 parts per thousand, is proportional to dietary non-grass%. This paper describes the development of a faecal near infrared (NIR) spectroscopy calibration equation for predicting faecal delta C-13 from which dietary grass and non-grass proportions can be calculated. Calibration development used cattle faeces derived from diets containing only C-3 non-grass and C-4 grass components, and a series of expansion and validation steps was employed to develop robustness and predictive reliability. The final calibration equation contained 1637 samples and faecal delta C-13 range (parts per thousand) of [12.27]-[27.65]. Calibration statistics were: standard error of calibration (SEC) of 0.78, standard error of cross-validation (SECV) of 0.80, standard deviation (SD) of reference values of 3.11 and R-2 of 0.94. Validation statistics for the final calibration equation applied to 60 samples were: standard error of prediction (SEP) of 0.87, bias of -0.15, R-2 of 0.92 and RPD of 3.16. The calibration equation was also tested on faeces from diets containing C-4 non-grass species or temperate C-3 grass species. Faecal delta C-13 predictions indicated that the spectral basis of the calibration was not related to C-13/C-12 ratios per se but to consistent differences between grasses and non-grasses in chemical composition and that the differences were modified by photosynthetic pathway. Thus, although the calibration equation could not be used to make valid faecal delta C-13 predictions when the diet contained either C-3 grass or C-4 non-grass, it could be used to make useful estimates of dietary non-grass proportions. It could also be ut :sed to make useful estimates of non-grass in mixed C-3 grass/non-grass diets by applying a modified formula to calculate non-grass from predicted faecal delta C-13. The development of a robust faecal-NIR calibration equation for estimating non-grass proportions in the diets of grazing cattle demonstrated a novel and useful application of NIR spectroscopy in agriculture.

Managing parthenium weed across diverse landscapes: prospects and limitations

Parthenium is a weed of global significance affecting many countries in Asia, Africa, and the Pacific Islands. Parthenium causes severe human and animal health problems, agricultural losses as well as serious environmental problems. Management options for parthenium include chemical, physical, legislative, fire, mycoherbicides, agronomic practices, competitive displacement and classical biological control. The ability of parthenium to grow in a wide range of habitats, its persistent seed bank, and its allelopathic potential make its management difficult. No single management option would be adequate to manage parthenium across all habitats, and there is a need to integrate various management options (e.g. grazing management, competitive displacement, cultural practices) with classical biological control as a core management option.

Processes leading to the detection of tropical weed infestations during an eradication program.

The authors identify and track processes that have resulted in the detection of six tropical weeds targeted for eradication. The habitats and distributions of these species make detection by field officers and members of the public more likely than targeted searches. The eradication program is increasing the scope of detection processes by conducting and documenting activities to improve weed recognition amongst public, government and industry stakeholders.

Foods of pigeons and doves in fragmented landscapes of subtropical eastern Australia

We report dietary items of pigeons and doves from northern New South Wales and southern Queensland, obtained from opportunistic sampling of the gut contents of dead birds and observing foraging birds. Most records were from fragmented rainforest habitats, which now support abundant invasive fleshy-fruited plants. The fruits and seeds of invasive plants, particularly Camphor Laurel Cinnamomum camphora, formed the dominant food of several of the species sampled, although in some cases these birds appear to destroy most of the ingested seeds in the gizzard, thereby not contributing to weed dispersal. We also describe the first records of White-headed Pigeons Columba leucomela eating flowers and Brown Cuckoo-Doves Macropygia amboinensis eating flower buds. Camphor Laurel, via flowers, green and ripe fruits, and seeds, provided food for White-headed Pigeons in the Goolmangar district of New South Wales throughout the entire year. Seventy percent of the plant species whose fruits and seeds were recovered from the gut had not previously been recorded as food items for those bird species, illustrating how little is known about the diets of pigeons and doves in fragmented Australian landscapes.

Predicting dispersal and recruitment of Miconia calvescens (Melastomataceae) in Australian tropical rainforests

Miconia calvescens (Melastomataceae) is a serious invader in the tropical Pacific, including the Hawaiian and Tahitian Islands, and currently poses a major threat to native biodiversity in the Wet Tropics of Australia. The species is fleshy-fruited, small-seeded and shade tolerant, and thus has the potential to be dispersed widely and recruit in relatively intact rainforest habitats, displacing native species. Understanding and predicting the rate of spread is critical for the design and implementation of effective management actions. We used an individual-based model incorporating a dispersal function derived from dispersal curves for similar berry-fruited native species, and life-history parameters of fecundity and mortality to predict the spatial structure of a Miconia population after a 30 year time period. We compared the modelled population spatial structure to that of an actual infestation in the rainforests of north Queensland. Our goal was to assess how well the model predicts actual dispersion and to identify potential barriers and conduits to seed movement and seedling establishment. The model overpredicts overall population size and the spatial extent of the actual infestation, predicting individuals to occur at a maximum 1,750 m from the source compared with the maximum distance of any detected individual in the actual infestation of 1,191 m. We identify several characteristic features of managed invasive populations that make comparisons between modelled outcomes and actual infestations difficult. Our results suggest that the model’s ability to predict both spatial structure and spread of the population will be improved by incorporating a spatially explicit element, with dispersal and recruitment probabilities that reflect the relative suitability of different parts of the landscape for these processes.