title: Holocene carbon dynamics at the forest-steppe ecotone of southern Siberia.
abstract: The forest-steppe ecotone in southern Siberia is highly sensitive to climate change; global warming is expected to push the ecotone northwards, at the same time resulting in degradation of the underlying permafrost. To gain a deeper understanding of long-term forest-steppe carbon dynamics, we use a highly resolved, multiproxy, palaeolimnological approach, based on sediment records from Lake Baikal. We reconstruct proxies that are relevant to understanding carbon dynamics including carbon mass accumulation rates (CMAR; g C m-2yr-1) and isotope composition of organic matter (δ13CTOC). Forest-steppe dynamics were reconstructed using pollen, and diatom records provided measures of primary production from near- and off-shore communities. We used a generalized additive model (GAM) to identify significant change points in temporal series, and by applying generalized linear least-squares regression modelling to components of the multiproxy data, we address (1) What factors influence carbon dynamics during early Holocene warming and late Holocene cooling? (2) How did carbon dynamics respond to abrupt sub-Milankovitch scale events? and (3) What is the Holocene carbon storage budget for Lake Baikal. CMAR values range between 2.8 and 12.5 g C m-2yr-1. Peak burial rates (and greatest variability) occurred during the early Holocene, associated with melting permafrost and retreating glaciers, while lowest burial rates occurred during the neoglacial. Significant shifts in carbon dynamics at 10.3, 4.1 and 2.8 kyr bp provide compelling evidence for the sensitivity of the region to sub-Milankovitch drivers of climate change. We estimate that 1.03 Pg C was buried in Lake Baikal sediments during the Holocene, almost one-quarter of which was buried during the early Holocene alone. Combined, our results highlight the importance of understanding the close linkages between carbon cycling and hydrological processes, not just temperatures, in southern Siberian environments.
authors.affiliation: Environmental Change Research Centre, Department of Geography, UCL, London, WC1E 6BT, UK.
authors.forename: Anson William
authors.initials: AW
authors.lastname: Mackay
authors.affiliation: Department of Biology and Bjerknes Centre for Climate Research, University of Bergen, PO Box 7803, Bergen, N-5020, Norway.
authors.forename: Alistair W R
authors.initials: AW
authors.lastname: Seddon
authors.affiliation: NERC Isotope Geosciences Facilities, British Geological Survey, Nottingham, NG12 5GG, UK.|Centre for Environmental Geochemistry, University of Nottingham, Nottingham, NG7 2RD, UK.
authors.forename: Melanie J
authors.initials: MJ
authors.lastname: Leng
authors.affiliation: Steinmann Institute of Geology, Mineralogy and Paleontology, University of Bonn, Nussallee 8, 53115, Bonn, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Heumann
authors.affiliation: Environmental Change Research Centre, Department of Geography, UCL, London, WC1E 6BT, UK.
authors.forename: David W
authors.initials: DW
authors.lastname: Morley
authors.affiliation: Department of Radioisotopes, Institute of Physics - CSE, Silesian University of Technology, Konarskiego 22B, 44-100, Gliwice, Poland.
authors.forename: Natalia
authors.initials: N
authors.lastname: Piotrowska
authors.affiliation: Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, PO Box 9825, Beijing, 100029, China.
authors.forename: Patrick
authors.initials: P
authors.lastname: Rioual
authors.affiliation: School of Geography, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
authors.forename: Sarah
authors.initials: S
authors.lastname: Roberts
authors.affiliation: School of Geography, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
authors.forename: George E A
authors.initials: GE
authors.lastname: Swann
mesh_terms: D002244:Carbon; D057486:Carbon Cycle; D002980:Climate; D057231:Climate Change; D065928:Forests; D019015:Geologic Sediments; D012800:Siberia
chemical_list: D002244:Carbon
keywords: Holocene; Lake Baikal; abrupt climate change; carbon; forest-steppe ecotone; palaeolimnology; permafrost