Quantifying carbon burial in northern forested lakes since the Anthropocene

English Abstract:

The northern forested zone is one of the most important areas for the processing of carbon (C) on an annual basis. Lakes play an important role in this carbon cycle burying large amounts of organic-C in their sediments. Estimates of organic-C burial in boreal lakes are poorly constrained and do not account for possible increases in burial rates driven by global ecosystem change during the last century. To address this issue, we used a large set of ²¹⁰Pb-dated sediment cores to determine spatial and temporal trends in organic-C burial over the last 180 years across the northern forests of continental North America. We found that baseline organic-C burial was negatively correlated with latitude and positively correlated with mean annual temperature. Additionally, mean post-1950 rates represent nearly a 2-fold increase over background rates and a 4- to 13-fold increase over average Holocene estimates. Up-scaling the mean lake C-burial rate observed in this study to the whole boreal forest biome could account for as much as 10% of the total organic C stored in lake sediments since the Holocene. With future disturbance regimes in the boreal forest biome, lake sediment may become an even more important site of C burial.