Ph Brown

Developing a regional ecological risk assessment: a case study of a Tasmanian agricultural catchment.

A regional ecological risk assessment was conducted for the Mountain River catchment in Tasmania, Australia. The Relative Risk Model was used in conjunction with geographic information systems interpretations. Stakeholder values were used to develop assessment endpoints, and regional stressors and habitats were identified. The risk hypotheses expressed in the conceptual model were that agriculture and land clearing for rural residential are producing multiple stressors that have potential for contamination of local waterbodies, eutrophication, changes in hydrology, reduction in the habitat of native flora and fauna, reductions in populations of beneficial insects in agricultural production systems, increased weed competition in pastures, and loss of aesthetic value in residential areas. In the risk analysis the catchment was divided into risk regions based on topography and land use. Stressors were ranked on likelihood of occurrence, while habitats were ranked on percentage land area. Risk characterization showed risks to the maintenance of productive primary industries were highest across all risk regions, followed by maintenance of a good residential environment and maintenance of fish populations. Sensitivity analysis was conducted to show the variability in risk outcomes stemming from uncertainty about stressors and habitats. Outcomes from this assessment provide a basis for planning regional environmental monitoring programs.

The physiological basis of containerised tree seedling ‘transplant shock’: a review

Summary Tree seedlings are planted on sites of widely differing climatic, edaphic and vegetative characteristics. Seedling transplant shock, defined as seedling mortality or impaired growth soon after planting, has been reported across this spectrum of planting conditions. Thus, transplant shock is used to describe a phenomenon that embraces many distinct physiological responses to stress. This review lists and discusses the potential sources of transplant shock for containerised tree seedlings and suggests options for minimising its detrimental effects for a range of specific causes. Through an understanding of the physiological basis underlying transplant shock under a given set of conditions, it may be possible to eliminate, or at least minimise, the effects of transplant shock on containerised tree seedlings soon after planting.

Clomazone dissipation in four Tasmanian topsoils

Abstract Clomazone dissipation was examined in four soils in field experiments. Field half-lives were 6 to 59 d (average of four field sites was 35 d) for ferrosol (clay loam), kurosol (loamy sand), sodosol (silt loam), and vertosol (light clay). The Hoerl equation provided a better fit to the measured field concentration at all four sites than did a first-order equation. The order of clomazone dissipation rate was ferrosol > sodosol > kurosol > vertosol. Clomazone desorption varied with soil type, with apparent Kd values of 3.6, 1.7, 1.8, and 2.4 for ferrosol, sodosol, kurosol, and vertosol, respectively. Clomazone residues became more strongly sorbed with time, as indicated by desorption hysteresis, but detectable concentrations were present in all soils 1 yr after application. The data indicate that the potential for carryover injury to crops is greatest in the kurosol and least in the ferrosol. Nomenclature: Clomazone.

Effect of shadecloth tree shelters on cold-induced photoinhibition, foliar anthocyanin and growth of Eucalyptus globulus and E. nitens seedlings during establishment

The effects of shadecloth tree shelters on cold-induced photoinhibition, foliar anthocyanin and growth of Eucalyptus globulus Labill. and Eucalyptus nitens (Deane & Maiden) Maiden seedlings were assessed between planting (in early spring) and the age of 23 weeks. The experimental site was at 350 m above sea level (asl), which is considered marginal for establishment of E. globulus (but not E. nitens) plantations in Tasmania because of low mean minimum temperatures. Conditions within 3 weeks of planting induced severe photoinhibition in non-shaded seedlings. This was associated with increased anthocyanin and photodamage in non-shaded E. nitens and E. globulus. As a result, there was 20p mortality in non-shaded E. globulus. In contrast, shaded seedlings of both species had levels of photoinhibition and anthocyanin that were largely similar to those before planting and there was no photodamage. Levels of anthocyanin indicated that its synthesis responded to the severity of photoinhibition. Height growth and levels of mortality indicated that cold-induced photoinhibition, and not frost tolerance alone, determines the range of environments where E. globulus can be successfully planted. In contrast, the tolerance of E. nitens seedlings to cold-induced photoinhibition may be a factor in the demonstrated success of this species as a high-altitude plantation species.

Post-pollination capsule development in Eucalyptus globulus seed orchards

Low capsule set is a major factor limiting seed production in Eucalyptus globulus seed orchards. Trials were conducted in E. globulus seed orchards in Tasmania, Australia, to identify the timing of capsule development and abortion, as well as the influence of pollination type, the number of ovules fertilised and weather events on capsule set. Controlled pollination (CP), mass supplementary pollination (MSP), open pollination (OP) and isolated unpollinated control (UP) treatments were performed on 21 genotypes in an orchard in southern Tasmania in 2004–2005 and on six genotypes in a higher-altitude orchard in north-western Tasmania in 2005–2006. No capsules were set in the UP control treatment, and capsule set was significantly lower following CP than OP and MSP. The major period of capsule abortion occurred between 20 and 80 days after pollination for all pollination methods across both sites, coinciding with the period of capsule growth. A positive correlation between the number of fertilised ovules per aborted capsule and the length of time capsules were held on the tree was recorded. Given that capsule abortion occurred during a period of fruit growth and that capsules with the lowest number of fertilised ovules aborted first, it is argued that fertilisation level and the level of resource competition are major factors determining capsule abortion.

The role of BoFLC2 in cauliflower (Brassica oleracea var. botrytis L.) reproductive development

Genetic, association, and expression studies indicate that a mutation in BoFLC2 explains much of the variability in cauliflower curd formation, curd growth rate, and flowering time.

Using Next-Generation Sequencing to Contrast the Diet and Explore Pest-Reduction Services of Sympatric Bird Species in Macadamia Orchards in Australia

Worldwide, avian communities inhabiting agro-ecosystems are threatened as a consequence of agricultural intensification. Unravelling their ecological role is essential to focus conservation efforts. Dietary analysis can elucidate bird-insect interactions and expose avian pest-reduction services, thus supporting avian conservation. In this study, we used next-generation sequencing to analyse the dietary arthropod contents of 11 sympatric bird species foraging in macadamia orchards in eastern Australia. Across all species and based on arthropod DNA sequence similarities ≥98% with records in the Barcode of Life Database, 257 operational taxonomy units were assigned to 8 orders, 40 families, 90 genera and 89 species. These taxa included 15 insect pests, 5 of which were macadamia pests. Among the latter group, Nezara viridula (Pentatomidae; green vegetable bug), considered a major pest, was present in 23% of all faecal samples collected. Results also showed that resource partitioning in this system is low, as most bird species shared large proportion of their diets by feeding primarily on lepidopteran, dipteran and arachnids. Dietary composition differed between some species, most likely because of differences in foraging behaviour. Overall, this study reached a level of taxonomic resolution never achieved before in the studied species, thus contributing to a significant improvement in the avian ecological knowledge. Our results showed that bird communities prey upon economically important pests in macadamia orchards. This study set a precedent by exploring avian pest-reduction services using next-generation sequencing, which could contribute to the conservation of avian communities and their natural habitats in agricultural systems.

Pollination biology of oilseed poppy, Papaver somniferum L

Although poppies (Papaver somniferum L.) are one of the oldest cultivated plants relatively little is known of their pollination biology. We have investigated the relative importance of wind and insects in the pollination of poppies and identified potential insect pollinators. Wind pollination was found to be negligible, insect pollination was responsible for the majority of out-crossing, and self-pollination was the dominant mode of poppy fertilisation. Honeybees and flies were identified as the main potential cross-pollinators of Tasmanian poppies. Using a transgenic poppy field trial in which approximately 50% of the pollen grains produced were transgenic, we have determined the level of pollen-mediated gene flow by scoring over 50 000 seeds for the presence of a selectable marker gene. Gene flow was measured using a 10-m buffer area that surrounded the field trial. It was highest at 0.1 m with 3.26% of seeds found to be transgenic and declined over distance with 1.73% transgenic seeds at 0.5 m, 1.80% at 1 m, 0.86% at 2 m, 0.34% at 5 m, 0.12% at 9 m, and 0.18% at 10 m. These results demonstrate that under Tasmanian conditions, pollen-mediated gene flow occurs at modest levels in poppies that are in close proximity to each other and is most probably mediated by honeybees and flies.

Rhizome dormancy and shoot growth in myoga (Zingiber mioga Roscoe).

Abstract After the senescence of above ground plant parts the rhizomes of myoga undergo a period of dormancy. The length of this dormancy period and the requirement for chilling to break dormancy are examined in this paper. Myoga rhizome segments were capable of initiating shoot growth 6 weeks after excision from a recently senesced dormant mother plant. A period of chilling was not required for shoot growth, but chilling at 4°C for 3 weeks immediately after excision resulted in shoot development in newly divided myoga rhizome segments which would otherwise not have sprouted until after a 6-week dormancy phase. Longer storage periods before planting and increased duration of chilling treatments decreased the variability in the sprouting response of rhizome segments. Chilling at 4°C for 2–4 weeks was the most effective treatment for promoting uniform sprout emergence and subsequent flower production. Shoot growth rate and the number of vegetative shoots produced by the rhizome was not affected by chilling treatments. Increasing the length of chilling, promoted earlier sprouting and flowering, but may have decreased the weight of the flower buds produced.

The impact of flower density and irrigation on capsule and seed set in Eucalyptus globulus seed orchards

Low capsule set is a major factor limiting the productivity of Eucalyptus globulus seed orchards. This study tested the effect of flower density, as well as two common irrigation techniques on capsule and seed set. Ramets with high flower density had significantly lower capsule set (69.7%) than those with low flower density (81.7%). In a regulated deficit irrigation trial, the non-irrigated ramets set a higher proportion of capsules (63.6%) than the ramets that received conventional irrigation (CI) (51.4%). In a partial root zone drying (PRD) trial, capsule set was highest in the absence of irrigation (74.7%) followed by the PRD treatment (67.8%) and then CI (53.7%). The CI treatment tended to produce the highest number of seed per capsule. Increased water availability resulted in increased vegetative growth, which was associated with higher levels of abortion in developing capsules but those surviving tended to have higher seed set. It is argued that the observed effects of irrigation and flower density can be explained by resource competition between vegetative and reproductive growth as well as competition among reproductive structures themselves.