A pile of second growth logs, with large yellow rings of sapwood at the exterior, piled in a clearing.

When does a tree reach maturity?

The photo at the top of this page shows a pile of second growth logs at Mount Elphinstone, on the Sunshine Coast. The yellow ring on the outside is sapwood, which carries water and minerals to the crown of the tree. It both contains more water and is softer than the darker heartwood at a trees core. As trees mature, the sapwood layer grows smaller. 

In ‘Quality Forestry always takes time,’ David Shipway wrote: 

“In terms of wood quality, sapwood is weak and unstable, has high moisture and sugar content, and thus shrinks, stains and decays quickly; while heartwood is drier and compressed (more stable), stronger (mature lignin fibre), and more durable (resinous). Sapwood products are not very diverse: One can make useable toilet paper and temporary artifacts out of it if you’re quick, but any solid sapwood product will need added chemical wood preservatives. Heartwood on the other hand is good lasting material for houses, boats, furniture, musical instruments and all the many traditional woodcrafts that have been passed down to us through the ages and are still relevant and essential today.”

Shipway used the following chart of a Douglas Fir to show how the proportion of sapwood in an ‘adolescent’ 80 year old log is much greater than in a more mature 180 year-old. 

Heartwood vs Softwood – From David Shipway, Quality Forestry Always Takes Time

A lot of authorities classify 250-year old trees as ‘old growth.’ 

In A Mature Forest Ecosystem,’ another one of the founders of the Cortes Community Forest Co-operative, Bruce Ellingsen, points out that a very complex ecosystem grows up in mature forests

“ …Studies have shown that epiphytes in a healthy, older forest steadily introduce nutrients into the system at a rate comparable to the amount a farmer would apply on his land to grow successive crops. These “free natural inputs” are permanently lost when successive harvests occur over short periods.”

“Why? Because when a forest is felled and harvested, the epiphytes die and release their contained nutrients within a few years. The epiphyte community is only slowly re-established in a young forest, taking 50 – 80 years to begin the process and 150 -250 years to regain most of the varieties that exist in a mature forest. Only when that point is reached is the epiphytic community again capable of delivering the nutrients needed to maintain and sustain a healthy forest.”

Ellingsen also said we need to stop focusing on trees and consider the forest as an ecosystem.

“What does it take to keep such a system healthy, thriving and able to maintain its long-term ability to provide those benefits we desire?”

(Read more)

(I sent this information out in an email this morning, then decided why not share it with everyone.)

Top credit: A pile of second growth logs at Mount Elphinstone, on the Sunshine Coast, used in the Wilderness Committee’s BC Timber Sales Hotspots Guided Tour – photo by Emily Hoffpauir, Wilderness Committee.

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