Tree Assessment: Case Study 2

Image 1: Hoop Pine – Araucaria cunninghamii. S.E.  Queensland.
Height: 26.1 meters. DBH: 2.3 meters (co-dominant). Crown Spread: 19m  

Assignment:

Despite the above tree being in a peri-urban / agriculture location, due to its “specimen” value and prominence in the landscape it is considered by myself to be a high retention value tree. Occasional pruning has been required in the past to maintain adequate clearance from vehicular traffic and the electrical infrastructure located on the opposite side of the road.

Target and Site:

A moderate use road and high voltage electrical infrastructure are within the target zone of the tree. It can be assumed that the tree pre-dates the current road meaning that root injury has occurred in the past. However, on the opposite side of the tree from the road is a low use “horse paddock”, meaning that the tree has access to large volumes of exploitable soil. 

Tree Condition:

A large decayed cavity exists (see image 2 & 3) at the base of the tree between the co-dominant stems on the eastern side of the tree. Additionally, there is little or no wound wood formation at the opening to the cavity, suggesting that the tree is not reacting sufficiently to this decay. Nevertheless, the crown density and foliage colour of the tree would indicate that it is in good health.

Image 2: Large decaying cavity at the base of the co-dominant stems.  
Image 3: Large decaying cavity at the base of the co-dominant stems.  

Analysis:

When comparing the trees health to the decay identified at its base it can be assumed that structural failure is the greatest threat to this tree’s useful life expectancy. Furthermore, if the failure of the left-hand stem (as pictured above) was to occur, large scale disruption would befall both the electrical network and transport infrastructure in the area.

Recommendations:

  1. Although counter intuitive to practices which minimise the proliferation of decay in a trees structure, the installation of a cabling support system in the trees crown could increase its useful life expectancy.
  2. Good tree healthcare cultural practices such as mulching and the application of silicon rich fertilizer (ROMERO et al. 2011) could help the tree counteract the decay evident at its base.
  3. Electrical impedance tomography is required to assess the quality of the remaining sound wood at the base of the tree.
  4. Continued short interval inspection is required to ascertain the speed at which the decay cavity is forming at the base of the tree.