Nurse Logs

Life and death are inextricably linked in the old-growth forest and nowhere is this more evident than in the important role of nurse logs. A nurse log is a fallen tree that serves as the growing site for young plants. Nurse logs are especially important for western hemlocks and Sitka spruce as they provide an elevated platform for the seedlings to grow free from the dense competition of shrubs and forbs already established on the forest floor. In fact, seedling densities may be nearly five times as high on nurse logs as on the ground and nurse logs may support nearly three times as many species of moss as the surrounding forest floor.

The influence of nurse logs continues for centuries after they rot away, you can often find “colonnades” of immense Sitka spruces growing in a clear line deep in the rainforest. These enormous rows of pillars appear to be more the product of human architecture than natural occurrences. This is because centuries ago each of these spruces would have germinated on a fallen tree. Though the original log has long since rotted away, the positions of these giant trees still reflect the straight beam of that long-ago nursery.

It’s not only trees that these nurse logs support, but also a huge range of rainforest creatures: fungi mine the dead wood for nutrients, insects burrow under the bark, pacific wrens nest in the huge upturned root-wads, and salamanders take shelter under the logs. These incredible forest nurseries are a hallmark of the old-growth forest, where the slow death of ancient trees is the mechanism of forest renewal and rebirth.