Trees Jerry Dicker

TREES

JERRY DICKER BA (Oxon), DTEO (Man), Tech Cert (Arbor A)

58 High Street, Thornbury, BS35 2AN, Phone 01454 416945 Mobile: 07798 741872
email jerry@treesjerrydicker.co.uk website: www.treesjerrydicker.co.uk

PICUS SONIC TOMOGRAM – EXAMPLE 2

Prepared for: Erewhon Tree Park

Explanation of tomograms and limitations:

The PICUS Sonic Tomograph detects and shows differences in the ability of wood to transmit sound waves. It does not differentiate between decay or cavities. Both are shown as pale blue or white.

Dark colours (black to brown) in the tomogram indicate areas of the trunk’s cross section where the sound travels relatively fast – compared to violet and blue areas where the sound travels relatively slowly. Green indicates the area between fast and slow sound transmission.

The numbered red dots show the sensor positions. Sensor 1 indicates the north side of the tree. The red line indicates 33% of tree diameter.

The wood is coloured according to relative sound velocities measured. Brown represents solid wood. The colours green, violet and blue indicate increasing degrees of decay.

All recommendations in this report are based on assessment of the tomogram in relation to external features observed. No climbing inspections, drilling, core samples or excavations were undertaken.

Tree: Scots Pine

An over mature tree, height 23m, dbh 1030mm, with an irregular crown containg heavy branch wood. Fungal fruiting bodies of Sparrassis crispa have been observed for several years. Photograph 1 was taken 2^nd October 2003.

Photo 1: Sparassis crispa, Oct 2003

Photo 2: tomography, March 2004

External features observed, related to tomogram:

The reading was taken at a height of 0.3m, where the circumference was 3590mm. The position is shown by the horizontal white tape in the picture. Photograph 2 shows modules 5, 6, 7, 8 & 9. I suspect, but am unsure, that the fruiting body was photographed approximately between sensors 8 & 9.

Date tomogram was taken: 21/3/04

Conclusions

The tomogram shows 68% solid wood (brown), and 19% decay or cavity (blue and purple), with 13% wood affected to some extent (green). At this height the ratio of thickness of residual wall of solid wood to radius of the tree (t/R ratio) is more than 33%. Stem fracture usually occurs only when the t/R ratio is less than 33%.

It seems likely that the cause of the decay is the fungus Sparassis crispa so the likelihood of windthrow is related to possible brittle fracture in the root plate.

The nature of the decay caused by this organism is a brown rot developing mainly in the root system, but also in the heartwood of the lower trunk. Given that the tomogram indicates a considerable area of rot at a height of 30 cm, it is to be expected that the roots are also affected. It is difficult to establish the extent of decay in the roots. I was present while a test with a resistograph was conducted, drilling diagonally down into the roots near sensors 6 to 8. No evidence of decay was found.

Recommendations

Re-examine the tree during the period August to November, to assess the size and distribution of any Sparassis crispa fruiting bodies.
Conduct drilling tests on the roots in the immediate vicinity of the fruiting bodies.
Conduct further tomograph tests annually to ascertain the rate of increase of the decayed wood.

Jerry Dicker, 26.3.04