title: Early land use and centennial scale changes in lake-water organic carbon prior to contemporary monitoring.
abstract: Organic carbon concentrations have increased in surface waters across parts of Europe and North America during the past decades, but the main drivers causing this phenomenon are still debated. A lack of observations beyond the last few decades inhibits a better mechanistic understanding of this process and thus a reliable prediction of future changes. Here we present past lake-water organic carbon trends inferred from sediment records across central Sweden that allow us to assess the observed increase on a centennial to millennial time scale. Our data show the recent increase in lake-water carbon but also that this increase was preceded by a landscape-wide, long-term decrease beginning already A.D. 1450-1600. Geochemical and biological proxies reveal that these dynamics coincided with an intensification of human catchment disturbance that decreased over the past century. Catchment disturbance was driven by the expansion and later cessation of widespread summer forest grazing and farming across central Scandinavia. Our findings demonstrate that early land use strongly affected past organic carbon dynamics and suggest that the influence of historical landscape utilization on contemporary changes in lake-water carbon levels has thus far been underestimated. We propose that past changes in land use are also a strong contributing factor in ongoing organic carbon trends in other regions that underwent similar comprehensive changes due to early cultivation and grazing over centuries to millennia.
authors.affiliation: Department of Ecology and Environmental Science, Umeå University, 901 87 Umeå, Sweden; and carsten.meyerjacob@gmail.com.
authors.forename: Carsten
authors.identifier: http://orcid.org/0000-0002-8208-496X
authors.initials: C
authors.lastname: Meyer-Jacob
authors.affiliation: Department of Ecology and Environmental Science, Umeå University, 901 87 Umeå, Sweden; and.
authors.forename: Julie
authors.initials: J
authors.lastname: Tolu
authors.affiliation: Department of Ecology and Environmental Science, Umeå University, 901 87 Umeå, Sweden; and.
authors.forename: Christian
authors.initials: C
authors.lastname: Bigler
authors.affiliation: Environmental Change Research Centre, University College London, London WC1E 6BT, United Kingdom.
authors.forename: Handong
authors.initials: H
authors.lastname: Yang
authors.affiliation: Department of Ecology and Environmental Science, Umeå University, 901 87 Umeå, Sweden; and.
authors.forename: Richard
authors.initials: R
authors.lastname: Bindler
mesh_terms: D000383:Agriculture; D000818:Animals; D002244:Carbon / Q000032:analysis*; D057486:Carbon Cycle; D004784:Environmental Monitoring; D005060:Europe; D019015:Geologic Sediments / Q000737:chemistry; D006801:Humans; D060106:Lakes / Q000737:chemistry*; D009656:North America; D010163:Paleontology
chemical_list: D002244:Carbon
keywords: Holocene; carbon cycling; lake-water quality; land use; paleoecology