Motivation
Most forest health indicators are species-specific or point-in-time. We lack standardised metrics for how well an ecosystem recovers after a disease event — a critical gap for long-term management.
Methods
We analysed 15 years of plot data from 32 mixed-species stands across Norway and Sweden, covering four major disease events (ash dieback, root rot, pine needle blight, beech bark disease).
Stability was quantified using three indices:
- Resistance (R): how little biomass was lost during the event
- Recovery (Rec): rate of return to pre-event biomass levels
- Resilience (Res): R × Rec combined score
Results
Mixed-species stands showed 2.3× higher resilience scores than monocultures. Stands with ≥4 tree species recovered 60% faster on average.
Soil organic matter content was the single strongest predictor of both R and Rec (r² = 0.71).
Implications for Management
These findings support diversity-based planting strategies and highlight soil health maintenance as a key lever for long-term ecosystem stability. We have developed a simple scoring tool for field practitioners — available on request.