Spelling strategies for recovery of pasture condition

This work will progess and extend recommendations and guidelines for use of integrated wet season spelling in Queenslands savannahs and woodlands. The research will generate a greater ecological and pasture production understanding of pastures and soils that exist in C land condition areas (major landtypes), and their recovery. Practical, cost-effective spelling regimes will be developed. Research will be conducted on-property with small plot exclosures and plots with controlled utilisation levels, examining ecological responses to different spelling regimes. This information will improve bio-economic modelling capacity. Industry consultations with producers and field staff will drive implementation of the recommendations arising.

The accuracy of varietal selection using factor analytic models for multi-environment plant breeding trials

Modeling of cultivar x trial effects for multienvironment trials (METs) within a mixed model framework is now common practice in many plant breeding programs. The factor analytic (FA) model is a parsimonious form used to approximate the fully unstructured form of the genetic variance-covariance matrix in the model for MET data. In this study, we demonstrate that the FA model is generally the model of best fit across a range of data sets taken from early generation trials in a breeding program. In addition, we demonstrate the superiority of the FA model in achieving the most common aim of METs, namely the selection of superior genotypes. Selection is achieved using best linear unbiased predictions (BLUPs) of cultivar effects at each environment, considered either individually or as a weighted average across environments. In practice, empirical BLUPs (E-BLUPs) of cultivar effects must be used instead of BLUPs since variance parameters in the model must be estimated rather than assumed known. While the optimal properties of minimum mean squared error of prediction (MSEP) and maximum correlation between true and predicted effects possessed by BLUPs do not hold for E-BLUPs, a simulation study shows that E-BLUPs perform well in terms of MSEP.

Ghost fishing in the pot fishery for blue swimmer crabs Portunus pelagicus in Queensland, Australia

Blue swimmer crabs (Portunus pelagicus) are an economically important crab caught in baited traps throughout the Indo-west Pacific and Mediterranean. In Australia they are traditionally caught using rigid wire traps (approximate to pots) but there has been a recent increase in the use of collapsible pots constructed from polyethylene trawl mesh. Two experiments were conducted in Moreton Bay, Queensland, to determine the ghost fishing potential of lost crab pots on both target and bycatch species and to evaluate the differences between traditional and contemporary pot designs. A lost contemporary, collapsible trawl mesh pot will catch between 3 and 223 R pelagicus per year after the bait has been exhausted, while a traditional wire mesh pot would catch 11-74 crabs peryear. As most fishers now use the collapsible trawl mesh pots, ghost fishing mortality could be as high as 111,811-670,866 crabs per year. Bycatch retention was also higher in contemporary designs. Periods of strong winds appeared to increase the ghost fishing potential of lost pots. The use of escape gaps, larger mesh sizes and construction options that allow for the deterioration of entrance funnels to minimise ghost fishing are recommended to reduce environmental impacts.

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.

Northern Grazing Systems Project Development

Control of grazing distribution, management of stocking rate, wet season spelling and fire

A guide to the process of Mitchell grass recovery

In western Queensland, severe drought conditions began in late 2001 and did not generally ease until the 2008/09 summer. Despite the ability of Mitchell grass plants to become dormant during drought, a large proportion of plants appeared to be dead rather than drought-dormant by the end of the 2002/03 summer. Tillers and remaining leaves were blackened and unpalatable to livestock. The term Mitchell grass dieback was coined by producers and other observers to describe what had occurred, although most were confident that the grass would recover with the breaking of the drought. Mitchell grass plants generally failed to respond to widespread average summer rains in early 2004 (> 250 mm). Observation suggested that moisture had penetrated to a soil depth of about 60 cm and a response from plants was expected. When there was no general response, research into the reasons for this was initiated (NBP.348 'Mitchell grass death in Queensland: extent, economic impact and potential for recovery'; 2005-07). This included an investigation of discrete areas of pasture that had responded to the 2003-04 summer rain. Further declines in condition of Mitchell grasslands occurred between winter 2005 and winter 2006 and, by 2006, field surveys indicated that 53% of this pasture community was in poor (C) condition, primarily due to dieback. Measurements at some sites suggested practices such as wet season spelling and burning can pre-condition Mitchell grass pasture for greater resistance to drought-induced dieback. However, the casual mechanisms and the effective timing and frequency of these practices remained unclear.

Reproductive variation in naturally occurring populations of the weed Parthenium hysterophorus (Asteraceae) in Australia

Parthenium weed, an annual herb native to tropical America, causes severe economic, human, and animal health and environmental impacts in Australia and in many countries in Asia, Africa, and the Pacific. There is little known about variation in reproductive output in naturally occurring populations of this weed. This information is vital to develop plant population models, devise management strategies to reduce seed output, and formulate parthenium weed pollen-induced human health (e.g., dermatitis and hay fever) risk assessment. Here, the variations in the number of capitula produced by the parthenium weed at two sites in Queensland, Australia, over a 4-yr period are reported. Under field conditions, parthenium weed produced up to 39,192 capitula per plant (> 156,768 seeds per plant), with majority of the plants (approximate to 75%) producing between 11 and 1,000 capitula, and less than 0.3% of the plants producing more than 10,000 capitula (> 40,000 seeds per plant). The number of capitula per plant in the field (297 +/- 22) was much lower than those reported from glasshouse and laboratory studies. Plant biomass contributed to 50 to 80% of the variation in capitulum production between plants within plots at each site, and weed density accounted for 62 to 73% of the variation in capitulum production between plots within each site. As plant size is directly correlated with reproductive output, plant size distributions in parthenium weed can be used to estimate effective population size. Information on variation in reproductive output will be used to implement management strategies to reduce parthenium weed seed output, resulting in reduced soil seed bank and weed seed spread.

Separating grazing and rainfall effects at regional scale using remote sensing imagery: A dynamic reference-cover method

Remote detection of management-related trend in the presence of inter-annual climatic variability in the rangelands is difficult. Minimally disturbed reference areas provide a useful guide, but suitable benchmarks are usually difficult to identify. We describe a method that uses a unique conceptual framework to identify reference areas from multitemporal sequences of ground cover derived from Landsat TM and ETM+ imagery. The method does not require ground-based reference sites nor GIS layers about management. We calculate a minimum ground cover image across all years to identify locations of most persistent ground cover in years of lowest rainfall. We then use a moving window approach to calculate the difference between the window's central pixel and its surrounding reference pixels. This difference estimates ground-cover change between successive below-average rainfall years, which provides a seasonally interpreted measure of management effects. We examine the approach's sensitivity to window size and to cover-index percentiles used to define persistence. The method successfully detected management-related change in ground cover in Queensland tropical savanna woodlands in two case studies: (1) a grazing trial where heavy stocking resulted in substantial decline in ground cover in small paddocks, and (2) commercial paddocks where wet-season spelling (destocking) resulted in increased ground cover. At a larger scale, there was broad agreement between our analysis of ground-cover change and ground-based land condition change for commercial beef properties with different a priori ratings of initial condition, but there was also some disagreement where changing condition reflected pasture composition rather than ground cover. We conclude that the method is suitably robust to analyse grazing effects on ground cover across the 1.3 x 10(6) km(2) of Queensland's rangelands. Crown Copyright (c) 2012 Published by Elsevier Inc. All rights reserved.

Sustainable grazing management for temporal and spatial variability in north Australian rangelands – a synthesis of the latest evidence and recommendations

Rainfall variability is a major challenge to sustainable grazing management in northern Australia, with management often complicated further by large, spatially-heterogeneous paddocks. This paper presents the latest grazing research and associated bio-economic modelling from northern Australia and assesses the extent to which current recommendations to manage for these issues are supported. Overall, stocking around the safe long-term carrying capacity will maintain land condition and maximise long-term profitability. However, stocking rates should be varied in a risk-averse manner as pasture availability varies between years. Periodic wet-season spelling is also essential to maintain pasture condition and allow recovery of overgrazed areas. Uneven grazing distributions can be partially managed through fencing, providing additional water-points and in some cases patch-burning, although the economics of infrastructure development are extremely context-dependent. Overall, complex multi-paddock grazing systems do not appear justified in northern Australia. Provided the key management principles outlined above are applied in an active, adaptive manner, acceptable economic and environmental outcomes will be achieved irrespective of the grazing system applied.

High-anthocyanin strawberries through cultivar selection

BACKGROUND: Diets high in fruit and vegetables are known to have significant health benefits. This is in part due to the presence of phytochemicals, which possess potential protective health benefits. This study focuses on the ability of strawberries to be bred for higher anthocyanin content. This is a major contributor to the characteristic colour and nutritional value of ripe strawberries, together with phenolic acids, ascorbic acid and total antioxidant capacity. RESULTS: Anthocyanins in five commercial strawberry cultivars and three breeding lines were assessed. This led to the discovery of one breeding line (BL 2006-221) as an exceptional source of anthocyanins (approximate to 1 g kg1 fresh weight), with approximately double the levels of current commercial cultivars. Temperature was shown to influence anthocyanin extraction, with 40 degrees C being the best extraction temperature using the accelerated solvent extraction (ASE) method. Hue angle and anthocyanin concentration showed a good correlation (r2 = 0.69). CONCLUSION: The new breeding line BL 2006-221 has the potential to be used in the development of phytochemically rich strawberry cultivars. Using hue angle as a screening tool for total anthocyanin concentration and extraction of anthocyanins from strawberries by ASE at 40 degrees C would support such cultivar development. (c) 2012 Commonwealth of Australia

Deriving optimal fishing effort for managing Australia's Moreton Bay multispecies trawl fishery with aggregated effort data

Deriving an estimate of optimal fishing effort or even an approximate estimate is very valuable for managing fisheries with multiple target species. The most challenging task associated with this is allocating effort to individual species when only the total effort is recorded. Spatial information on the distribution of each species within a fishery can be used to justify the allocations, but often such information is not available. To determine the long-term overall effort required to achieve maximum sustainable yield (MSY) and maximum economic yield (MEY), we consider three methods for allocating effort: (i) optimal allocation, which optimally allocates effort among target species; (ii) fixed proportions, which chooses proportions based on past catch data; and (iii) economic allocation, which splits effort based on the expected catch value of each species. Determining the overall fishing effort required to achieve these management objectives is a maximizing problem subject to constraints due to economic and social considerations. We illustrated the approaches using a case study of the Moreton Bay Prawn Trawl Fishery in Queensland (Australia). The results were consistent across the three methods. Importantly, our analysis demonstrated the optimal total effort was very sensitive to daily fishing costs—the effort ranged from 9500–11 500 to 6000–7000, 4000 and 2500 boat-days, using daily cost estimates of $0, $500, $750, and $950, respectively. The zero daily cost corresponds to the MSY, while a daily cost of $750 most closely represents the actual present fishing cost. Given the recent debate on which costs should be factored into the analyses for deriving MEY, our findings highlight the importance of including an appropriate cost function for practical management advice. The approaches developed here could be applied to other multispecies fisheries where only aggregated fishing effort data are recorded, as the literature on this type of modelling is sparse.

Climate savvy grazing (Developing improved grazing and related practices to assist beef production enterprises across northern Australia to adapt to a changing and more variable climate)

There is uncertainty over the potential changes to rainfall across northern Australia under climate change. Since rainfall is a key driver of pasture growth, cattle numbers and the resulting animal productivity and beef business profitability, the ability to anticipate possible management strategies within such uncertainty is crucial. The Climate Savvy Grazing project used existing research, expert knowledge and computer modelling to explore the best-bet management strategies within best, median and worse-case future climate scenarios. All three scenarios indicated changes to the environment and resources upon which the grazing industry of northern Australia depends. Well-adapted management strategies under a changing climate are very similar to best practice within current climatic conditions. Maintaining good land condition builds resource resilience, maximises opportunities under higher rainfall years and reduces the risk of degradation during drought and failed wet seasons. Matching stocking rate to the safe long-term carrying capacity of the land is essential; reducing stock numbers in response to poor seasons and conservatively increasing stock numbers in response to better seasons generally improves profitability and maintains land in good condition. Spelling over the summer growing season will improve land condition under a changing climate as it does under current conditions. Six regions were included within the project. Of these, the Victoria River District in the Northern Territory, Gulf country of Queensland and the Kimberley region of Western Australia had projections of similar or higher than current rainfall and the potential for carrying capacity to increase. The Alice Springs, Maranoa-Balonne and Fitzroy regions had projections of generally drying conditions and the greatest risk of reduced pasture growth and carrying capacity. Encouraging producers to consider and act on the risks, opportunities and management options inherent in climate change was a key goal of the project. More than 60,000 beef producers, advisors and stakeholders are now more aware of the management strategies which build resource resilience, and that resilience helps buffer against the effects of variable and changing climatic conditions. Over 700 producers have stated they have improved confidence, skills and knowledge to attempt new practices to build resilience. During the course of the project, more than 165 beef producers reported they have implemented changes to build resource and business resilience.