EVALUATING THE IMPORTANCE OF LAKE CARBON BURIAL AS A COMPONENT OF LANDSCAPE-WIDE CARBON ACCUMULATION (MINNESOTA, USA)

Lakes constitute a long-term continental sink of organic carbon (OC), accumulating and preserving organic material in their sediments for centuries to millennia or longer. Dated sediment cores (²¹⁰Pb, ¹³⁷Cs) from 116 lakes in Minnesota, USA reveal substantial spatial and temporal variation in OC burial rates linked to anthropogenic land-use practices (Dietz et al. 2015; Anderson et al. 2013). Cumulative OC burial in Minnesota lakes over the past 150 years amounts to ~40 Tg C, 40% of which can be attributed to anthropogenic enhancement. Modern annual burial (~0.40 Tg C/yr) equals merely 1.5% of statewide carbon emissions (as CO₂) from fossil fuel combustion – and increased OC burial due to anthropogenic influences counterbalances 0.9% of emissions – but is this a proper metric for evaluating the importance of the lacustrine carbon sink? Here, lakes are considered in a landscape context, comparing their long-term rates of OC burial to those which may occur in other environments (peatlands, mineral-soil wetlands, upland soils, etc.) over similar timescales, using data from available literature. Comparison suggests that lakes are a significant component (>10%) of natural landscape carbon sinks in Minnesota.

Anderson, N.J., Dietz, R.D., and Engstrom, D.R. (2013). Land-use change, not climate, controls organic carbon burial in lakes. Proceedings of the Royal Society B 280:1769.

Dietz, R.D., Engstrom, D.R., and Anderson, N.J. (2015). Patterns and drivers of change in organic carbon burial across a diverse landscape: insights from 116 Minnesota lakes. Global Biogeochemical Cycles 29: 798-727.