Moderate drop in water table increases peatland vulnerability to post-fire regime shift

Area of Science:

• Ecology
• Environmental Science
• Climate Change Science

Background:

• Northern and tropical peatlands store significant global carbon reserves due to prolonged waterlogged conditions.
• Peatland carbon legacies are threatened by drainage, leading to burning and carbon loss, as seen in tropical regions.
• The impact of moderate drying on northern peatlands, compared to severe tropical drainage, remains unclear.

Purpose of the Study:

• To quantify the post-wildfire recovery of a northern peatland under decadal drainage.
• To assess if moderate drying in northern peatlands triggers vegetation shifts similar to those in disturbed tropical peatlands.

Main Methods:

• Utilizing a unique long-term experimental setup.
• Monitoring vegetation composition changes following wildfire in a drained northern peatland.

Main Results:

• Moderate drying, as predicted for northern regions, induced a vegetation shift comparable to severely drained tropical peatlands.
• The combination of moderate drainage and wildfire transformed the peatland from a moss-dominated, carbon-accumulating state to a shrub-grass ecosystem.
• This new ecosystem is characterized by low-intensity, high-frequency wildfires, further depleting stored peat carbon.

Conclusions:

• Moderate drying and subsequent wildfire can destabilize northern peatland carbon stores.
• The shift to a shrub-grass ecosystem creates a positive feedback loop, increasing future fire frequency and carbon loss.
• Northern peatlands face a significant risk of transitioning from carbon sinks to carbon sources under predicted climate change scenarios.