Chemical element concentrations and accumulation in boreal mire ecosystems in Finland

The role of mires providing ecosystem services as element sequestration and long-term storage was determined from two major mire types, fens and bogs, in boreal Finland. A detailed analysis of 35 different chemical element concentrations, dry bulk density and age of the peat layers were used to determine the long-term element accumulation rates. Differences in several element concentrations showed a strong regional pattern. The median concentrations of non-metals such as N, S and P were 1.6 to 1.8-fold higher in fens compared to bogs. Similarly, the median heavy metal concentrations were approximately 2.2 times higher in fens. Despite the significantly lower C accumulation rates of fens, the accumulation rates of many other elements were of the same magnitude between fens and bogs. The most significant differences in the long-term accumulation rates were found within P, Al and several heavy metals (Cr, Fe, Ni, Th, U, V), which were significantly higher for fens compared to bogs. However, the accumulation rates of K and Mg were significantly lower in fens, indicating a great depletion and plant uptake. The results of this study demonstrate that intact mires contribute to multiple ecosystem service goals simultaneously, including the crucial C sequestration and storage but also other long-term element sequestration and storage including both non-metals and metals.