08/1787 - Response to Information Request [As Published] · 132008.1787

 

 

 

 

 

 

 

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Scahaven Development Pry Lid- 9-19 Hastings Street Noosa QLD 4567 7 4
All trees to be retamed on a construction site should have protected root zoncs o
that are measured off the DBH of the trunk via the Matheny & Clark (Harris . oe
2004, & Matheny & Clark 1998) formula or the usc of the British Standards
(BS 5837:2005) for protecting trees, with knowledge of the critical root zone *
which takes into account structural stability issucs. ‘
The following table shows required tree protection zone distances based on ‘
Tree No 48, given that the tree has a DBH of 600mm and is regarded as
mature.
, | Tree Protection Method Required Tree Protection Zone
(radius from tree trunk)
Matheny & Clark-
Species of good tolerance —
90mm per 10mm of Trunk DBH § 400 mm
Matheny & Clark-
Spccics of moderate tolerance —
120mm per 10mm of Trunk DBH 7200 mm
BS 5837:2005 :
Singlé Stem tree- radius 7 200 mm
Single Stem tree- area 162.88 square metres
Critical Root Zone 3 000 mm a
(5 times trunk diameter)

 

 

 

 

Table No {- tree protection zones under different tree protection methods for oe
Tree No 48. cae

 

Using the Matheny & Clarks method a previous understanding of a tree er
species tolerance to disturbance (good, moderate, or poor) is required. As seen mo
in Table No 1, the tolerances of good and moderate are compared, but usually 7
Ficus obliqua is considered to have a good tolerance to disturbance given . ae

previous experiences. Thus a minimum of 5.4 mctres is required to adcquatcly
protect the tree where disturbance is all around the tree.

‘The British Standard (BS 5837-2005) would require a protection zone based

on the trunk diameter, either as a radial distance or as an area. Therefore a -
minimum of 7.2 metres or an area of 163 square metres is required. Under ‘we
BS 5837:1991 this radial distance could be reduced by 1/3 for 120 degrees of aid

the total circle, but under BS 5837:2005 an offset of the distance up to 20% in 5 |
one direction maybe undertaken on open grown trecs.

The final method of critical root zone is used to calculate the bare minimum
protection zonc required to stop damage to the major woody roots and
structural root formations that maintain tree stability. Critical root zone is
based on the trunk DBH times by 5, thus giving a minimum of 3.0 metres.
For Ficus obliqua and its tolerance to root disturbance, this distance would be
used for transplanting (Harris ct al 2004, page 210-212).

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Leaf and Limb Horticultural Consultancy®
Prepared by Samuel Cowie 29" of January 2009