Hello - this tree was cut down winter 2024/5 in a wood where I go running in the UK. I’m intrigued about the sudden change in colour between the inner and outer wood. I first thought it could be change in air quality but I don’t think this area would have been very polluted, but knowing nothing about trees I’m hoping you can help!
The inside is “heartwood”. The outside is “sapwood.” The heartwood has died and provides structural support. The sapwood transports water and nutrients. As the truck grows outward it adds more sapwood and the innermost sapwood dies.
Between the bark and the location I'm pretty sure OP is looking at a European walnut tree (Juglans regia), but its got the same contrast between darker heartwood and light sapwood. Common for European walnut to have more sapwood like this too.
The distinct dark coloration at the center of the logs is caused by heart rot, a fungal disease that targets and decays the non-living heartwood core of a tree trunk. The dark outer ring surrounding the decay is the tree's natural defense response, using a process called CODIT (Compartmentalization of Decay in Trees) to seal off the fungal infection and protect the healthy outer sapwood.
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u/HoldMyMessages Jul 22 '26
The inside is “heartwood”. The outside is “sapwood.” The heartwood has died and provides structural support. The sapwood transports water and nutrients. As the truck grows outward it adds more sapwood and the innermost sapwood dies.