ABSTRACT The costs of maintaining an urban street tree over its lifecycle have been considered in cost models. One used in Australia is a typical relationship between the cost and functional and aesthetic benefits of the urban shrub mass. But are these curves typical of larger, long-lived urban street trees growing under Australian conditions? The costs of maintaining an urban street tree under Australian management regimes, including purchase and planting costs of a common street tree species, herbicide and mulching costs, the cost of irrigation over the first summer after spring planting and of formatively pruning the young tree were calculated based on data obtained from Australian local government agencies. The research-modelled management of an urban tree under five scenarios based upon planting a 2–3 m tall tree with a safe useful life expectancy of 50 years. Scenarios included annual maintenance, regular pruning on a 5-year cycle after 15 years and a major arboricultural intervention in the final decade. The impact of longer lifespans of 100 or 150 years was also modelled. The curves demonstrated that costs associated with a street tree are high in the first 2–3 years of its life but much higher in the final year of life leading to removal but differed in shape from other models. The lifetime costs of maintaining a street tree depending on the management scenario are between AUD$2800 and AUD$6220 or AUD$56 and AUD$124.40 per annum. Doubling the lifespan of a street tree reduces the annual management cost by 30%.

SummaryThe harvesting of Onion Grass (Romulea rosea) corms by flocks of Sulphur‐crested Cockatoo (Cacatua galerita) is well known. Individual birds and large flocks feed on the weed in pastures, grasslands and recreational turf. Flocks of Sulphur‐crested Cockatoo were observed feeding on Onion Grass at seven sites along the Maribyrnong River at Keilor, Victoria. Flock size and feeding habits were noted, as were the depth of corms, the time taken to remove corms from the ground and the number of eaten and lifted but uneaten corms. From the data collected, it was estimated that an individual bird can extract and eat about 200 plants per hour and that even a small flock can consume several thousand plants in a feeding session. Corms were typically within 20 mm of the soil surface and were removed primarily by the cockatoo with its beak, but the left foot was sometimes used to excavate the corm from the soil. Flock feeding sessions lasted from about 0.5 to 2.5 hours, but feeding by individual or pairs of birds was often shorter. Plants that had been removed from the soil appeared to have intact corms, but all that was left were the outer scales. Of the plants removed from the soil, only 6% had intact corms attached. The removal of large numbers of Onion Grass plants could impact on their population numbers over time if there was repeated annual harvesting.

The direct effects of atmospheric and re-radiated heat from surfaces surrounding a street tree can affect its establishment, growth and development through high-temperature-induced injury. Sunscald is a symptom of direct heat injury to plant tissue that occurs on the trunk and branches as a result of high solar radiation causing the dehydration and death of plant tissues. This research was designed to investigate the impact of different paving surfaces, tree orientation at the time of planting and high ambient temperatures on the establishment of roadside trees in Melbourne, Australia. Thirty young Platanus × acerifolia trees were planted along the centre median of a major road and on the west side, directly adjacent to each tree, a 0.5 m2 paved surface was installed in a timber plinth box, with a 50 mm gap between the tree trunk and plinth. Four different materials were used to surface the boxes – concrete and organic mulch (recycled wood) for which there were seven replicates and asphalt and granitic sand for which there were eight replicates. Fourteen of the trees had their north facing orientation from the nursery maintained and 16 trees were rotated 180° so that their orientation was reversed and they faced south. In the morning, mulch and asphalt were up to 2 °C hotter than concrete and granitic sand, but by late afternoon, concrete and asphalt were on average 5 °C hotter than mulch and granitic sand. The data on afternoon temperatures showed mulch and asphalt being significantly hotter than concrete and granitic sand by 10 °C or more, but by late afternoon mulch had cooled by as much as 30 °C. The asphalt remained the hottest surface throughout the day and into the evening. While not significant (p = 0.077) reversing orientation at planting appeared to interact with pavement surface to reduce shoot tip extension. This research established a relationship between the occurrence of sunscald on the trunks and poor tree growth which warrants further investigation as the Australian climate warms.

Dormant buds such as lignotuberous and epicormic buds are adaptations possessed by plants growing in stressful environments. Eucalyptus obliqua is a species occupying a wide range of habitats in south-eastern Australia, which displays ecotypic diversity. Seedlings of E. obliqua from provenances with and without lignotubers were subject to heat stress at 40–100°C for durations ranging from 2 to 128 min. Seedlings from a single population were also stressed by decapitation, which left two, four or eight leaves intact. While the upper stems and leaves of the heated seedlings from different provenances reacted in the same way to the treatments imposed, seedlings that lacked lignotubers died at lower temperatures and at shorter durations than seedlings that possessed lignotubers. Production of lignotuberous shoots did not necessarily guarantee seedling survival as the mortality rates of lignotuberous shoots were high, ranging from 55% to 100%. The recoveries of the heated and decapitated seedlings were similar, but the possession of foliage enhanced the survival of lignotuberous shoots that were produced after treatment. The possession of lignotuberous and epicormic buds by tree species is an important adaptation to stress that has implications for urban tree management. Lignotuberous shoot production is usually a last-resort survival mechanism.

Two experiments were conducted to test the hypothesis that trees able to establish in urban soils will have a higher-than-average tolerance to the higher mechanical impedance and soil strength of compacted soils. Experiment 1 tested the ability of the roots of Corymbia metadata (spotted gum, syn. Eucalyptus maculata), Lophostetnon confertus (brush box), Corymbia ficijolia (red flowering gum, syn. Eucalyptus ficifolia), and Agonis flexuosa (willow myrtle) seedlings to penetrate a sandy loam soil compacted to bulk densities of 1.4 and 1.8 mg • m~3 at 13% gravimetric moisture content. While roots of all species were able to penetrate the soil at the higher bulk density, total root penetration depth was reduced by 60% in all four species. Experiment 2 tested the ability of Corymbia maculata and C. ficijolia to penetrate soil compacted at bulk densities 1.4, 1.6, and 1.8 mg • m~3 at two moisture levels, 7% and 10% gravimetric moisture. At 7% moisture, both species were able to penetrate soil compacted to 1.4 and 1.6 mg • rrr3, but neither species was able to successfully penetrate soil compacted to 1.8 mg • m"3. At 10% moisture, both species were able to penetrate soil compacted to 1.4 and 1.6 mg • m~3. They also were able to successfully penetrate soil compacted to 1.8 mg • nr3, although with significantly less depth of penetration than at the two lower bulk densities.

Objective: To determine approximate time and severity of a porcine proliferative enteropathy (PPE) outbreak in a herd with a history of PPE; to compare average daily gain (ADG), average daily feed intake (ADFI), feed efficiency (F:G), and clinical impression of disease in clinically affected nonmedicated controls versus pigs medicated with 110 ppm (100 g per ton) of tylosin for 21 days followed by 44 ppm (40 g per ton) tylosin for an additional 21 days; and to follow pigs to market to determine effects of the outbreak on clinical PPE lesions detected at slaughter.

All aspects of tree growth and development are regulated by plant hormones and other growth-regulating substances. The most common of these compounds are the auxins, gibberellins, and cytokinins, but other substances such as ethylene and abscisic acid also have a significant impact on tree biology. Usually there is a complex interaction between the growth regulators to affect physiological responses. An understanding of plant growth regulators can significantly increase the capacity of arborists to effectively manage trees in urban landscapes. However, to effectively use plant growth regulators as a tool for tree management, arborists must understand the subtlety of their interactions. Furthermore, to achieve arboricultural objectives, arborists must also understand the nature of the biochemistry and importance of precise and targeted application of plant growth regulators. In an era of modern arboriculture practice, tree hormones and growth regulators are not just substances of control but tools of effective tree management.