Land use as a key driver of increased organic carbon burial in boreal lakes

Abstract The abundant lakes in the boreal region are an active zone for cycling of organic carbon (OC), functioning as simultaneous sources and sinks of atmospheric carbon dioxide. While previous studies have documented increased OC loading and accelerated carbon accumulation to inland waters, the drivers of this increase remain ambiguous. In this study we investigate carbon accumulation rates in 208 boreal lakes in the context of land use. We show that modern sediment carbon accumulation rates in boreal lakes have increased to median of 24.5 g m −2 y −1 , representing a roughly fivefold increase over Holocene record, mainly due to increased terrestrial organic carbon inputs. Land use has become the most significant predictor of modern lake sediment carbon accumulation with lake morphometrics primarily affecting the efficiency of carbon burial. Recalcitrant terrestrial carbon from forested and peatland areas is buried more effectively, whereas increased soil erosion and enhanced mineralization of labile OC from agricultural runoff reduces the relative burial of terrestrial OC.