Fire pattern in a drainage-affected boreal bog

Fire is an important natural disturbance element in the boreal zone, not only in the forested areas but also wetter peatland ecosystems. Predicted climate warming is expected to cause a moderate water-level drawdown in northern peatlands, which might result in increased frequency and severity of fires in boreal peatlands because of increase in fire-loading. We surveyed the fire pattern and the impact of drainage to the fire pattern on partly drained and pristine parts of a boreal raised bog using three sampling transects reaching from drainage-affected area to a pristine, fire-impacted bog area. We detected that dry bog hummock surfaces provided spreading routes for fire while hollow surfaces stayed almost intact. Drainage had promoted succession that lead to dominance of hummock vegetation. The lowered water level and abundance of hummock surfaces typical to the drainage-affected area was favourable for fire. The results suggest an increase in fire impact following drainage and that under changing climate bogs may become more vulnerable for fire.