242 Two leaves each from the north, south, east, and west facing direction were scanned. Soil bulk density was measured at the completion of the experiment using a Dormer split core soil corer with a 40-cm long sampling tube. Once the tube was 35 to 40 cm deep, it was removed, providing an undis- turbed core sample 4.8 cm in diameter. The cores were divided into three sections (0 to 10 cm, 10 to 20 cm, and 20 to 30 cm), and three samples were taken per block from randomly selected locations (3 samples per block, 3 depths, 16 blocks, 144 samples). The samples were placed in a Labec oven at 80° C for 24 hours, weighed, and the bulk density calculated by dividing dry weight by volume. A Rimik CP10a Cone pene- trometer was used to determine soil compaction. The probe was inserted into the soil approximately 30 cm from each location of the final bulk density tests. Three measurements were made in each block to a depth of 20 cm (48 samples). At final harvest, 20 months after planting, trees were cut at ground level and bagged. The bags were placed in an oven at 80° C and weighed one week later, then periodically until the weight stabilized. Because of the large volume of material, it took several months to complete drying. Roots were excavated from the blocks using an air compressor (130cfm) with a 1.9-cm diameter air hose and Kennard nozzle (3.0-cm diameter flattened to a 0.5-cm width) from which the air was expelled. Starting from the trunk, the soil was blown from the roots, exposing the root system. A 1.5t mini excavator was used to move the excess soil from the root system. North was marked on the trunk using a paint pen so that when the roots were lifted from the ground, orientation was preserved. While the roots were still in the ground, the length of the longest root growing to the north, south, east, and west was mea- sured for each tree. Each root system was cut up and the dry weight determined using the same method as for the trunks and foliage. Survey Five of the species from the previous experiment were surveyed growing as street trees within the suburban City of Hume (20 km from the centre of Melbourne), which manages approximately 80,000 street trees. Approximately 10 to 12% of street trees die within three years of planting, mainly due to vandalism. Fifteen C. maculata, L. confertus, Q. palustris, and 16 E. poly- anthemos planted for 24 months, and 15 O. europaea ©2019 International Society of Arboriculture Moore et al.: Growth and Establishment of Australian Street Trees ‘Tolley’s Upright’ planted for 36 months were sur- veyed. The trees were irrigated (20 and 40 L) every seven days in the first year and every 21 days for the second and third year after planting. For each species, three trees from five different streets were chosen by Stratified Random Selection. If the street was long, it was divided into sections, and trees were selected from each section and from both sides of the street, making sure they were not clustered, to give generalized data and a good representation of the tree growth and growing conditions along the street. Visual Tree Assessment (VTA) was undertaken using headings modified from Lonsdale (2001), includ- ing general information, tree characteristics, site con- ditions and usage, tree condition, and remedial works to improve tree health and reduce hazards (Fitzgerald 2003). The Tree Condition category was an assess- ment of the tree’s general condition and was divided into four sections: Roots, Trunk, Branches, and Foli- age. Each field had a 1 to 5 rating score, with 1 having major problems and 5 having no problems. There were 20 category fields in total, which provided a per- fect score of 100 points; the healthier the tree, the higher the score (Table 1). Bulk density was measured at two locations for each tree just outside the mulched area, 1 m from the trunk and parallel to the road. This was done to obtain accurate bulk density data, as the soil profile under the mulch had been disturbed during planting. The core sampling technique (Cass et al. 1998) was used to obtain core soil samples, which were oven dried at 80° C for 24 hours and then weighed. Samples were collected using a slide hammer constructed at the uni- versity that was similar to an Eijkelkamp, core cutter model RAW 2010/6, 08.09. A Rimik CP10a cone penetrometer was used to measure soil compaction. The readings were taken at a depth of 20 cm, and four readings were taken per site. Two of the readings were adjacent to the location of the soil samples for bulk density, and readings were taken 1 m from the tree trunk. The chlorophyll fluorescence of the foliage was measured as an indicator of the stress levels of the plant in the late morning and in the early afternoon. Individual leaf area was measured for each tree using the same leaves as measured for fluorescence and same method as in the experiment. Data were ana- lyzed using Minitab 16 and the ANOVA General Linear Model (GLM). The separation of each pair of means was done using LSD with significance at P < 0.05.
November 2019
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