One of the expert witnesses, Derek Yap, an arborist with Camphora said that the tree had "no visible signs of crack and cavities", based on his inspection after the tree fell and information preceeding the incident. In addition, he said that "about 70 per cent of the tree trunk at its 2m point was decayed". That extent of decay would significantly reduce the structural condition of the tree but the decay could not be observed from the outside of the tree.
A news article was published yesterday with the headline of "NParks disputes arborists’ diagnosis on tembusu tree in fatal incident" (Today Online, 31 Aug 2017).
A National Parks Board (NParks) representative, deputy director Elango Velautham, testified on 30 Aug 2017 that a 1.5m long "cavity" found during an inspection done on Sep 2016 was actually a "flute" (see definition below) This statement raises three points to be noted:
1. The inspection done on Sep 2016 was by NParks officers.
2. One of the independent arborist said that the tree had "no visible signs of crack and cavities" in his testimony on 17 Jul 2017.
3. It was not known whether the misdiagnosis was discovered before or after the tree fell.
Definition of a "flute".
An example of "flutes" - the grooves between buttress roots below the feet of the arborist on the tree. Photo credit: Today Online
The news article suggested that Elango's testimony contrasted with that of the two independent arborists. But could it be that his testimony actually supported the two independent arborists'?
Elango said that NParks arborists have written a statement to note that the flute was "wrongly perceived as a cavity" as a follow-up to the Sep 2016 inspection report. But it was not known whether the misdiagnosis was discovered before or after the tree fell.
The lawyer acting for Angara's family had questioned "the absence of documentary proof showing how the misdiagnosis was determined", as the written statement was not produced in court on 31 Aug 2017. If signs of decay (cavity) was observed from visual tree assessments, both independent arborists "agreed that further tests such as resistograph and ultrasound could be used to detect decay".
Bonus Curious Point
Arborist Derek Yap agreed that the roots might have been cut and leading to possible decay but another arborist, Richard Gordon Thomas from ArborCulture, said it was not clear that root had been cut. However, another news article - "Tembusu tree accident: Botanic Gardens official says there was 'no decay, no cavity'" (Channel NewsAsia, 30 Aug 2017) - mentioned that both arborists "agreed that the tree’s roots were in decay".
Bonus Bonus Curious Points
That same news article mentioned above wrote that Elango described a flute to be a “protruding structure” on a tree’s trunk formed in response to “environmental exertions” to the tree. Could it be that the journalist who wrote that or Elango confuse a flute with buttress roots?
Elango added that a Temusu tree is "very slow growing", and decays would "take a very long time to … destabilise a tree". Does he mean to suggest that the spread of decay is in pace with the growth of wood?
The structural stability of the tree would be impacted if the decay was extensive enough, in spite of the wood strength.
References
1. Tembusu tree that killed woman had no visible signs of decay, Today Online, 18 Jul 2017
2. NParks disputes arborists’ diagnosis on tembusu tree in fatal incident, Today Online, 31 Aug 2017
3. Tembusu tree accident: Botanic Gardens official says there was 'no decay, no cavity', Channel NewsAsia, 30 Aug 2017
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