Remarkable Longevity of Ancient Douglas Fir Wood

Royal BC Museum Botany Collection Reveals Value of BC Old-Growth Rainforests

by Heidi Guest, Collections Manager Natural History

During a recent inventory of items in the Botany collection of the Royal BC Museum, we unearthed an odd specimen with a rather fascinating history—a 42-centimetre long, 5-centimetre square block of wood with an approximately 100-year-old newspaper clipping and a photograph glued to it.

The newspaper article (from the BC Lumberman, according to a handwritten label) notes that the block of wood came from a Douglas fir “partially embedded in the soil about three miles north of Allco.” Active in the 1920s, Allco was a logging camp near Maple Ridge in the Fraser Valley. (The area is now the Alouette Prison for Women.) The article goes on to point out how extraordinary it is that this log would be so sound given that it was found in an area where conditions would be “very favourable to decay”, and that the “sound material extends clear to the outside of the log”.

Although the article does not state the age of the log, we can make an estimate. In the photograph, a man stands in front of the stump of a cedar that, according to the newspaper piece, was 250 years old when it was cut (nowadays we would estimate that it was at least twice that old), and the cedar’s roots almost engulf the Douglas fir log beneath it. We know the Douglas fir fell well before the cedar germinated, but how old was it when it fell?

If the man is about six feet (about 2 metres) tall, then the Douglas fir log is at least two metres thick. We counted 31 growth rings in the five-centimetre width of the wood block. If one growth ring appears per year you’d need 20 five-centimetre blocks to make up a metre—half the tree’s thickness; we only want to count from the centre to the edge—and 31 x 20 = 620. This means the tree took more than 600 years to achieve a radius of one metre.

But wait, there’s more! The wood section was cut from the log about 12 metres along its length. Who knows how long it took to grow from a seedling to reach that point—another few hundred years? And did the tree break when it fell? If so, how many more metres of height are we not able to account for? Given the size of the cedar that grew from it, this potentially 1,000-year-old log lay on the forest floor for perhaps another 1,000 years! It really is astounding that wood this hard and dense could have been lying there for so long without decaying. So how did wood like this form? By growing very slowly.

It takes millennia for a forest to develop the characteristics needed to support the growth of giant trees. Conditions were such that this tree could grow undisturbed in a cool, shady environment that, with the essential diversity of other plants, animals and insects that could have taken millennia to develop. Whatever the circumstances that created it, this 100-year-old block of wood can still tell a great story.