Arboriculture & Urban Forestry 45(6): November 2019 • Allocasuarina littoralis (Salisb.) L.A.S. Johnson, (Black Sheoak) • Corymbia maculata (Hook.) K.D. Hill and L.A.S. Johnson (Spotted Gum) • Cupressus sempervirens L. var. stricta (Ait.) (Mediterranean cypress) • Eucalyptus polyanthemos Schauer (Red Box) • Lophostemon confertus (R. Br.) P.G. Wilson and Waterhouse (Brushbox) • Olea europaea L. (European Olive ‘Tolley’s Upright’) • Quercus palustris Muenchh (Pin Oak) • Waterhousea floribunda (F. Muell.) B. Hyland (Weeping Lilly Pilly) They were grown in the research station at the University of Melbourne, Burnley College, 500 Yarra Blvd, Richmond, Australia. The soil of the research station is classified as a fine sandy loam. Plants were in 15-cm pots, except for O. europaea which were pur- chased in 20-cm pots, and Q. palustris were bare rooted. The block design comprised eight species, two treatment factors (compacted or uncompacted soil), and eight replicates, with each block containing all eight species, giving a total of 128 plants. Each block measured 12 × 5 m with trees planted at 1.5 m cen- ters. The compacted and uncompacted blocks were randomly allocated along with the location of each species within each block. The blocks were prepared by removing turf, ripping the soil using a tractor and single ripping blade to a depth of 80 cm with 40 cm between rip lines. The compacted blocks were com- pacted with a Dynapac CC900G ride-on vibrating roller. The target levels of compaction were greater than 2.5 MPa, and blocks were compacted one at a time, with four passes of the compactor. Bulk density was measured in all blocks using the volume excava- tion technique, in which a sample of soil is excavated and the hole filled with sand (or water) to determine its volume. The sample is dried and weighed and the dry weight of the soil sample is divided by the vol- ume of the hole to determine bulk density (Craul 1992; Lichter and Costello 1994). Trees were 30 to 40 cm tall at the time of planting, and their heights were recorded and trunk diameter measured at 20 cm above the soil using a NSK Elec- tronic Digital Calliper. A small paint mark was used to future trunk diameter measurements. Planting holes were dug in the uncompacted soil with position 241 a hand spade, but in compacted soil a mattock was used. Every two months, trunk diameter, canopy spread on the north/south and east/west orientations, and height (ground level to the tallest branch tip) were measured. For trees with multiple leaders or epicormic shoots, the original leader was measured, except where it had died; then the tallest shoot was measured. A 7.5-cm thick layer of mixed-particle size, organic mulch was applied to both soil treatments to suppress weed growth, reduce evaporation from the soil, and add organic matter. The mulch was maintained at a thickness of 7.5 cm. Over the 20 month growth period, the trees were checked two to three times per week to assess any damage, irrigation requirements, stake main- tenance or removal, mulch level, weeding require- ments, or occurrence of pest attack. In Australia, most street trees are not irrigated automatically, but many are hand-watered over the first few summers, so each plant was hand-watered with a hose until the water pooled on the surface, then watered a second time until the water pooled. Weeds were sprayed with Roundup (glyphosate 360 g/L, Monsanto Australia). Because of insect attack, C. maculata, E. polyanthemos, and W. floribunda were sprayed twice with Yates Pest Oil (839 g/L petroleum oil) at a rate of 25 mL/L. C. maculata was also treated once with Confidor (imidacloprid, at a rate of 1 g/L) for caterpil- lar infestations. Three C. sempervirens trees showed symptoms of cypress canker (Seridium species), and for two the affected foliage was removed, but a third was so badly affected that it was replaced. Sufficient trees were available for replacements, so with few mortalities and eight replicates there was no impact on statistical analyses. A portable Hansatech Plant Efficiency Analyser (PEA) was used to measure chlorophyll fluorescence (Fv/Fm) on the leaves of the trees except for A. litto- ralis and C. sempervirens, as their foliage was too fine for testing. Fv/Fm data are indicative of photo- synthetic efficiency, and when environmental stress impacts upon photosystem ll of tree leaves, there is a decrease in the value of Fv/Fm. The method used was to the manufacturer’s specifications, and four read- ings per tree were taken using leaves from north, south, east, and west facing sections of the canopy in the late morning and in the early afternoon over sev- eral days due to the large number of plants. Leaf area was measured, except for A. littoralis and C. semper- virens, with a LiCor Biosciences LI 3100C area meter. ©2019 International Society of Arboriculture
November 2019
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