Many different factors affect the time it takes for wood to rot, but spruce trees that die and fall to the forest floor usually disappear within 50 to 100 years. Pine logs on the forest floor remain there for 200 to 300 years.
One of the factors that determines how fast wood decomposes is the amount of resin in the wood. Pine is higher in resin than spruce. However, the length of time a pine tree remains composed before rotting is shorter if the tree grows in a forest that receives more rainfall because the trees produce less resin.
The environment plays a role in the time it takes for trees to rot. In northern Canada, the extreme cold freeze-dries trees. Some of the trees on the forest floors there are over 2 million years old.