Citation
Nurse Log Establishment in Pacific Northwest Forests
TL;DR
70% of western hemlock seedlings establish on nurse logs
Documents that approximately 70% of western hemlock and 40% of Sitka spruce seedlings establish on nurse logs in old-growth Pacific Northwest forests. This research provides the biological basis for understanding how infrastructure subsidies enable establishment in otherwise impossible environments.
The temporary subsidy (nurse log) enables permanent establishment - by the time the log decomposes (100-150 years), the tree is 20-30 meters tall with deep roots.
Key Findings from researchers (2000)
- 70% of western hemlock seedlings establish on nurse logs
- 40% of Sitka spruce seedlings establish on nurse logs
- Seedlings on nurse logs have 2-5× higher survival rates in first 5 years
- Nurse logs provide: elevated position, nutrients, fewer competing roots, looser substrate
- Logs take 50-100 years to decompose - investment for 2-3 generations