Implications of climate-disturbance interactions for northern peatland carbon cycling

Background/Question/Methods

Pristine peatlands have a number of stabilizing mechanisms that increase their resilience to stress and disturbance.  However, recent research has highlighted the potential for several regime shifts in northern peatlands associated with interactions between climate and disturbances. Here, I will highlight research from regional gradient, ecosystem manipulation, and chronosequence (space-for-time substitution) studies that focus on the role of climate-mediated disturbance (drought, wildfire, permafrost thaw) on peatland vegetation, carbon cycling, and energy balance.

Results/Conclusions

Thawing permafrost in peat plateaus leads to a state change with the creation of collapse scar bogs or fens, causing large changes in surface characteristics (i.e., vegetation, water table position) that have implications for slow processes such as turnover of old carbon stored in the historic permafrost pool.   As permafrost continues to thaw at a landscape scale, increasing influxes of heat from groundwater can serve as a positive feedback to thaw.  Experimental drainage of a forested peatland resulted in increased carbon pools associated with woody biomass and surface soils, but also increased combustion rates and ecosystem carbon losses during a naturally occuring fire event.  Together, long-term drainage and severe burning of a forested fen altered the trajectory of post-fire vegetation succession typical of more pristine sites, and likely will lead to the future conversion of these sites from fen to forest domains.  An understanding of the role of multiple or severe disturbances in affecting peatlands remains limited, yet is essential for predicting the fate of high latitude carbon stocks.