Article Figures & Data
Figures
- Figure 1.
Wind-thrown trees in Kew Gardens (UK) after the 1987 storm. Note the closeness of the tree to the pathway and infrastructure.
- Figure 2.
The spread and depth of a typical tree root system (Watson and Neely 1994).
- Figure 3.
Descending or sinker roots typical of urban tree root systems (modified from Watson and Neely 1994).
- Figure 4.
Windthrow due to the failure of windward roots and the buckling of leeward roots.
- Figure 5.
Skewed, elliptical root plate in response to prevailing wind.
- Figure 6.
A fallen elm (Ulmus spp.) in a prominent Melbourne park with waterlogging, lack of descending roots, shallow root plate, lateral root damage, and paved surface in evidence.
- Figure 7.
A fallen elm with a shallow root plate growing near a pathway; windward roots pulled from the soil, lack of descending roots, and a pool of water under the base of the tree two days after the major storm event of 2005. The tree has hinged close to the trunk on the leeward side.
- Figure 8.
Some of the many fallen elms growing along pathways in a public garden in Melbourne, Australia, after a major storm event in 2005. Both trees proved to be positive for criteria 1–6, and both have hinged close to the trunk on the leeward side.
- Figure 9.
Close-up of the base of one of the fallen elms after the 2005 storm, showing in excess of 300 mm fill around the trunk of the tree.
- Figure 10.
A fallen eucalypt in a forest roadside reserve. Note the waterlogged soils in a site where roadwork had altered drainage, as well as the lack of descending roots.
Tables
Failure pattern Effect on root system Consequence Type 1 A straight root is pulled directly from the soil Sudden failure as frictional forces between soil and tapered root are exceeded Type 2 A lateral root with many small lateral roots pulled Slower failure as there is a gradual failure after a major force is applied as small lateral roots progressively break Type 3 Major branched roots are pulled Failure occurs in abrupt steps as major root components break Factor Attributes to resist windthrow Soil Soil must resist fracture and remain dryer than its plastic limit Windward roots Longest 2–3 major windward roots must resist pulling out and breaking in tension; they must resist snapping in sheer Mass of tree Weight of the tree, including both aboveground mass and root plate mass, must be sufficiently great Leeward roots Leeward roots must resist buckling or hinging in compression and snapping in sheer Root plate Stem base and large roots must provide a wide stiff supporting platform that resists splitting - Table 3.
Criteria used in assessment of wind-thrown trees in Melbourne (modified from Moore 2004).
Criteria 1 Evidence of site or trenching works within four meters of trunk 2 Significant damage and/or decay to exposed lateral roots 3 Evidence of the loss of descending (sinker or vertical) roots 4 Evidence of soil compaction in immediate vicinity of the trunk 5 Presence of fill around base of tree 6 Indicators of waterlogging in immediate vicinity of the trunk 7 Canopy dieback and deadwood Genus No. Crit 1 Crit 2 Crit 3 Crit 4 Crit 5 Crit 6 Crit 7 Eucalyptus 18 7 14 16 11 4 9 10 Ulmus 30 28 29 29 25 21 23 10 Acacia 15 2 11 10 3 0 4 2 Cupressus 5 2 5 5 3 0 1 0 Melaleuca 4 0 3 3 2 0 2 0 Lophastemon 2 2 2 2 2 0 1 1 Populus 4 4 4 4 4 3 3 3 Ficus 2 2 2 2 2 2 2 0 Total 80 47 70 71 52 30 45 26 Trees positive for criterion (%) 58.8 87.5 88.8 65.0 37.5 56.3 32.5 - Table 5.
Comparison of assessment criteria for eighty fallen urban trees compared to fifteen wind-thrown forest trees.
Criterion Forest trees positive for criterion (%) Urban trees positive for criterion (%) Evidence of the loss of descending (sinker or vertical) roots 100 88.8 Significant damage and/or decay to exposed lateral roots 40 87.5 Evidence of soil compaction in immediate vicinity of the trunk 0 65.0 Indicators of waterlogging in immediate vicinity of the trunk 66.6 56.3 Evidence of site or trenching works within four meters of trunk 0 58.8 Presence of fill around base of tree 0 37.5 Canopy dieback and deadwood 80 32.5
Jump to section
- Article
- Abstract
- WHOLE-TREE FAILURE DURING STORM EVENTS
- THE INTERACTION OF TREE CANOPIES AND WIND
- THE ROLE OF ROOTS IN TREE STABILITY UNDER WIND LOAD
- MATURE ROOT SYSTEMS: THE ROOT PLATE, LATERAL AND DESCENDING ROOTS
- DATA FROM SITE INSPECTIONS OF WIND-THROWN URBAN TREES
- COMPARING WIND-THROWN FOREST AND URBAN TREES
- CONCLUDING DISCUSSION
- Acknowledgments
- LITERATURE CITED
- Figures & Data
- Info & Metrics
- References
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