©2023 International Society of Arboriculture 32 smallest size category, less than 10-cm diameter, were identified as being lost in 95.3% (286) of all trees (Table 8). While 34.3% (103) of trees did not appear to have been maintained, 49% (147) had evidence of pruning of small branches, and 16.7% (50) had large limbs pruned, usually due to the presence of power lines. The response of trees to pruning was noted (Table 8), and most trees appeared to respond well, with 228 of the 275 trees pruned (82.9%) having excellent to good responses and producing epicormic shoots. The gen- eral condition of the canopy for each tree was assessed (Table 11), and 93.3% (280) of trees had normal, healthy foliage, with 75% (225) of trees demonstrat- ing minor problems related to dead or dying branches or foliage. Of the 6.7% (20) of trees with serious health problems, 0.7% (2) had dead or dying leaves, 3.3% (10) showed evidence of serious insect damage, and 2.7% (8) had foliage of abnormal colour. Of these 8 trees, 75% (6) had greater than 80% abnormal foli- age, almost certainly due to viral infection, and 50% (4) of these also had serious insect damage. Trees were assessed for new growth between May and September. New growth was observed on 43% (129) of trees, and of these, 26.4% (34) had signifi- cant new growth. A majority of trees had some new growth in all months assessed, but there was consid- erably less new growth in August, which is in the Australian winter (starting on 1 June and concluding on 31 August). There was a lower proportion of trees that had heavy new growth in August than in other months (Table 12). In assessing the distribution of new growth across the canopy, 53.5% (69) of trees had new growth evenly through the canopy, 38.8% (50) had unevenly distributed new growth, and for the remaining 7.8% (10), growth was localised to epi- cormic shoot responses to damage. Trees were assessed to determine whether tree roots were exposed or whether there was movement of the surface caused by the roots (Table 8). Of the 300 trees, 25% (75) were identified as having a surface impact from the roots. Girdling roots were found on 2 (0.7%) of trees, and both had a DBH greater than 40 cm. The soil surface around the base of 8.3% (25) of trees was raised, possibly due to roots. Exposed roots were evi- dent on 16% (48) of trees, 7.7% (23) had roots that were greater in diameter than 10 cm, and 8.3% (25) had roots that were less than 10 cm in diameter. decay was found in 37.3% (112), with 5.7% (17) hav- ing areas of significant decay. Of the 112, 25.9% (29) of trees were exuding resin from main branches. Branches can be lost due to storms, poor health, or pruning. Missing lower branches were identified from post-pruning stubs or broken remains, and 22.7% (68) of trees had lost a branch greater than 20 cm in diameter. Of these 68 trees, 69.1% (47) had only one 20-cm or greater branch missing, and 19.1% (13) had 2 branches greater than 20 cm missing, while 11.8% (8) had 3 or more branches missing. Branches esti- mated to be between 10 and 20 cm in size were iden- tified as missing in 47% (141) of all trees, and 41.8% (59) of these had just one branch of this size missing; 27.7% (39) of trees had 2 missing; and 30.5% (43) had 3 or more missing branches. Branches in the Table 11. Health and condition of small branches, twigs, and foliage described by the number of dead or dying branches and the presence of abnormal foliage of Eucalyptus leucoxylon (n = 298). Dead or dying branches and/or twigs Number of trees Frequency (%) 1. No death evident 22 7.3 2. 0% to 20% 205 68.3 3. 21% to 40% 66 22.0 4. 41% to 60% 3 1.0 5. 61% to 80% 1 0.3 6. 81% to 100% 2 0.7 Abnormal foliage 1. Appears normal 280 93.3 2. 0% to 20% 8 2.7 3. 21% to 40% 5 1.7 4. 41% to 60% 0 0.0 5. 61% to 80% 1 0.3 6. 81% to 100% 6 2.0 Presence of decay and exudates 1. No decay detected 139 46.6 2. Minor areas of decay 159 53.4 3. Significant areas of decay 34 11.4 4. Exudates or resin present 164 55.0 5. Fungal fruiting bodies or cavities present 3 1.0 Moore and Chandler: The Potential of Yellow Gum as an Urban Street Tree
January 2023
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