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Dr Alex Shigo "Tree Autopsy"

Reading the Tree's Log

Dr. Alex L. Shigo doing an autopsy.


Trees keep a very accurate log of all events that affect their lives The log is kept in the wood, and to read that log you must under stand the simple language of tree anatomy. Trees respond to the ever changing environment, and to injuries and infections. Because pruning and removing trees are major activities of most tree companies. arborists have many opportunities to autopsy a tree and read its log.

Autopsy, which comes from the Greek word autopsia, means to see for yourself. It is often mistaken for the word for necropsy, which means the study of the dead. The usefulness of an autopsy depends on knowing where to look, what to look for, and the meaning of what you see. You must be able to see details fast. We have a special name for people who can see fast. We call them lucky!

Here is check list for some major features to look for and record when reading the tree's log.

1. Growth increments - tree age, patterns of wide or narrow increments, eccentric growth patterns, date when increments began to increase or decrease in width, colors.

2. Wood type - diffuse-porous, semi-ring porous, ring porous, conifer resinous, conifer non-resinous, tropical, monocot.

3. Energy reserves, I,KI to determine amount of starch and volume of wood with starch.

4. Wound history - date of wounds to the year, or, in some cases, the week they were inflicted.

5. Branch history - when branches died. If pruned, how they were pruned and the defect associated with the branches.

6. Cracks - boundaries from wounds, ring shakes, radial cracks, cracks in bark only, cracks in wood and bark, wetwood in cracks.

7. Animal wounds - bird peck wounds and ring shakes, squirrel wounds, other animal wounds.

8. Closure patterns of wounds - ram's horns, cracks, woundwood ribs, discolored wood associated with cracks.

9. Discolored wood and wetwood - patterns of infected wood, CODIT walls, callus, odors, internal checking patterns.

10. Decayed wood - white rot, brown rot, zone lines in rotted wood, CODIT walls, sporophores.

11. Resin ducts - traumatic ducts in non-resinous conifers.

12. Tyloses - traumatic tyloses in wood that does not normally form them.

13. Insects - galleries, in bark, in bark and wood, insect, ants, termites; galleries clean or full of frass.

14. Reaction wood - compression wood in conifers. (You cannot see tension wood.)

15. Injection and implant wounds - separate columns of discolored wood, or columns coalescing.

As you learn more about tree anatomy, many other details of the tree's log will become obvious.