Past, present, and future peatland carbon balance: An empirical model based on 210Pb-dated cores.
Boreal and subarctic peatlands today represent a large global carbon (C) reservoir. Existing models that describe organic matter accumulation in peatlands over thousands of years are inadequate for predicting short-term responses to changing climate. This paper develops a new, empirically based model that estimates net primary production (NPP) and depth-dependent decay rates (exponential decay k values) of near-surface peat. Application of the model to three sites in boreal Alberta indicates that today the sites are net sinks for atmospheric C at rates of 34-52 g Cm22yr21. Even without climate change, within 80-160 years, these sites will attain steady-state conditions with no further net C accumulation. Climate change scenarios in which NPP or k values are allowed to change gradually and linearly (at 0.1% per year) affect net C sequestration. Any scenario of decreasing NPP or increasing k values results in the peatlands switching from net sinks to net sources of atmospheric C within the next 20-62 years. Regional C balance of the peatlands in boreal, continental, western Canada will at best diminish in terms of strength of an atmospheric C sink and may well shift to becoming a source of atmospheric C. Shifts from sinks to sources of atmospheric C may occur within time frames that are similar in magnitude to the anticipated doubling of atmospheric CO2 by the middle of the 21st century.
|Main Author:||Wieder, R Kelman.|