Appendix B - Arborist Report 22 August 2025 · OPW16/0303.02

Arboricultural Impact Assessment - Palm Lakes Resort Cooroy - Revision 1 - IAS17818 - 22 August 2025

In addition to lateral root spread being underestimated, root depth in trees has also been grossly
exaggerated. Deep root systems or taproots are the exception rather than the rule. Most roots of most
trees are found in the very top of the soil. The vast majority of these roots are small non-woody
absorbing roots which grow upward into the very surface layers of the soil and leaf litter. This delicate,
non-woody system, because of its proximity to the surface, is very vulnerable to injury.”

Explanatory Note: The importance of gas exchange in soils

The fact that tree roots require oxygen to function is often misunderstood. Accessibility to available
oxygen and water within the soil structure is dependent on the integrity of soil structure within their
surrounds; when soils are compacted there is little space between soil aggregates with soil volume and
total pore space, especially macropore space diminished. In turn, good soil oxygenation and gas
exchange (Lonsdale) levels allow for successful function of tree roots. Oxygen levels in soils will typically
decrease as soil depth increases and /or soils are heavily compacted.

Macropore is the term used to describe the relatively large space between soil particles that is usually
air filled and allows for water movement and root penetration. Micropore is the term used to describe
the space between soil particles that is relatively small and likely to be water filled.

Compaction results from loads or stress forces applied to the soil as well as shear forces. When soil
within the root zone of a plant, including a tree, is compacted through either pedestrian or vehicular
traffic, or by the heavy weight of stored materials or machinery, the ability of water and oxygen to
penetrate the soil around the roots of living plants is compromised. Whilst tree roots are typically found
in the top 600mm of the soil horizon, vehicle traffic, in particular may cause significant compaction at
depths of 150–200 mm (the area in which most absorbing roots are located). (Refer Tree Function Note
above).

The degree of soil compaction will depend on weight of vehicles, number of movements, soil moisture
levels and clay content. Soil handling, stockpiling and transporting also tend to lead to the breakdown of
soil structure and thus to soil compaction. Vibration, as a result of frequent traffic or adjacent
construction activities, will also cause compaction of soil.

Contrary to the commonly held myth that all trees have tap roots, tree roots are typically located within
the top 600mm of soil. Just as leaves perform the vital function of photosynthesis, tree roots are vital
for the primary functions of anchorage, storage, absorption and conduction. Larger tree roots fulfil the
main functions of anchorage, storage and conduction and smaller more fibrous tree roots, which grow
primarily at the end of the main woody roots, fulfil a vital role in absorbing oxygen, essential mineral
elements and moisture from the soil, often through a symbiotic relationship with soil borne fungi
referred to as Mycorrhizae; the extent of root loss has the potential to jeopardise any or all of these
main functions and most importantly may compromise the structural integrity of an established tree
and its associated potential OH&S risk of failure occurring; any OH&S risk of potential failure in a high
use area such as public roads, is noteworthy for all the wrong reasons and should be of major concern
and avoided at all times. (Refer Appendix 2, Tree Function Note).




   Figure 3: Gas exchange in woody tissues: the diffusion of gases into and out of a particular region
                                              (Jaluzot)




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