Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Clim. Past Discuss., 9, 245–267, 2013 www.clim-past-discuss.net/9/245/2013/ Climate doi:10.5194/cpd-9-245-2013 of the Past CPD © Author(s) 2013. CC Attribution 3.0 License. Discussions 9, 245–267, 2013 This discussion paper is/has been under review for the journal Climate of the Past (CP). Vegetation Please refer to the corresponding final paper in CP if available. responses to interglacial warming A. V. Lozhkin and Vegetation responses to interglacial P. M. Anderson warming in the Arctic, examples from Lake El’gygytgyn, northeast Siberia Title Page Abstract Introduction 1 2 A. V. Lozhkin and P. M. Anderson Conclusions References 1 Northeast Interdisciplinary Scientific Research Institute, Far East Branch, Russian Academy Tables Figures of Sciences, 16 Portovaya Street, Magadan, 685000, Russia 2Earth & Space Sciences and Quaternary Research Center, University of Washington, Seattle, 98195-1310, USA J I Received: 28 August 2012 – Accepted: 3 September 2012 – Published: 15 January 2013 J I Correspondence to: P. M. Anderson ([email protected]) Back Close Published by Copernicus Publications on behalf of the European Geosciences Union. Full Screen / Esc Printer-friendly Version Interactive Discussion 245 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Abstract CPD Palynological data from Lake El’gygytgyn reveal responses of plant communities to a range of climatic conditions that can help assess the possible impact of global warm- 9, 245–267, 2013 ing on arctoboreal ecosystems. Vegetation associated with climatic optima suggests 5 two types of interglacial responses: one is dominated by deciduous taxa (the post- Vegetation glacial thermal maximum (PGTM) and marine isotope stage (MIS5)) and the second responses to by evergreen conifers (MIS11, MIS31). The MIS11 forests show a similarity to Picea- interglacial warming Larix-Betula-Alnus forests of Siberia. While dark coniferous forest also characterizes MIS31, the pollen taxa show an affinity to the modern boreal forest of the lower Amur A. V. Lozhkin and 10 valley in the Russian Far East. Despite vegetation differences during the thermal max- P. M. Anderson ima, all four glacial-interglacial transitions are alike, being dominated by deciduous woody taxa. Initially Betula shrub tundra established and was replaced by tundra with tree-sized shrubs (PGTM), Betula woodland (MIS5), or Betula-Larix (MIS11, MIS31) Title Page forest. The consistent occurrence of deciduous forest and/or high shrub tundra in all Abstract Introduction 15 interglaciations as they approach or achieve maximum warmth underscores the sig- nificance of this biome for modeling efforts. The El’gygytgyn data also suggest the Conclusions References possible elimination or massive reduction of arctic plant communities under extreme Tables Figures warm-earth scenarios. J I 1 Introduction J I 20 Marine and ice cores contain vital data that document fluctuations in past climate and Back Close provide insight into the possible causes of the observed paleoclimatic variability. How- ever, such records cannot provide information on the responses of biotic systems to Full Screen / Esc those changes. Most paleo-biotic records do not have the longevity, continuity, or tem- poral resolution of ocean and ice cores, which limits the comparison of long-term trends Printer-friendly Version 25 in biological and climatic data. Lake El’gygytgyn (Lake E), whose basin was created following a meteor impact ∼ 3.58 Ma ago, presents a rare exception having yielded a Interactive Discussion 246 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | continuous sedimentary record dating back ∼ 2.8 Ma (Melles et al., 2012). The loca- tion of the lake in arctic Chukotka (Fig. 1) provides a unique look into the response of CPD terrestrial ecosystems at northern high latitudes to a broad range of warm and cold 9, 245–267, 2013 conditions. 5 Several biological proxies have been examined in cores from Lake E (Brigham-Grette et al., 2007; Melles et al., 2012); we present here interpretations of past vegetation Vegetation based on palynological data. Previous research has shown that cool, dry intervals responses to are clearly marked in the Lake E record by a dominance of herb pollen (particularly interglacial warming Poaceae) and usually higher values of Selaginella rupestris spores (Lozhkin et al., A. V. Lozhkin and 10 2007; Matrosova, 2009). These spectra contrast to interglacial assemblages where arboreal pollen is at a maximum, herbaceous taxa are low, and spores are often dom- P. M. Anderson inated by Sphagnum. Continued research on a newly raised core shows that inter- glacial assemblages display vegetation and climatic variability both within and between Title Page isotope stages. For example, marine isotope stage (MIS) 11.3 and MIS31 have been ◦ ◦ 15 described as “super interglaciations” with maximum summer temperatures ∼ 4 to 5 C Abstract Introduction warmer than either MIS5.5 or the postglacial thermal maximum (PGTM; Melles et al., 2012). Conclusions References These warmer-than-present intervals are of particular interest for understanding pos- Tables Figures sible responses and feedbacks related to increasing global temperatures (e.g., Harri- 20 son et al., 1995; Kaplan et al., 2003). Both conceptual and quantitative models have J I considered two types of vegetation responses at northern high latitudes; one suggests the expansion of evergreen conifer forest northward across North America and much J I of Eurasia (e.g., Claussen, 1996; Kaplan et al., 2003), whereas the second postulates Back Close a dominance of broadleaf deciduous forest in current areas of tundra (e.g., Bonan et 25 al., 1990; Chapin and Starfield, 1997). Paleobotanical data are one means by which Full Screen / Esc these alternative scenarios may be evaluated. Although analysis continues on Lake E, sufficient palynological data are available to compare the vegetation responses during Printer-friendly Version the “super interglaciations” and the more moderate warming represented in MIS5.5 and the PGTM. Interactive Discussion 247 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2 Methods CPD One to two cm3 sediment samples were processed for palynological analysis follow- ing standard procedures used in preparing organic-poor samples (PALE, 1994). Sam- 9, 245–267, 2013 ples for MIS1-MIS2 and MIS4-MIS6 are from core PG1352, whereas core D1 provided 5 samples from MIS11-MIS12, and MIS 31. Pollen sums for interglacial spectra gener- Vegetation ally exceed 500 identified pollen grains. Percentages of individual taxa are based on responses to a sum of all arboreal, nonarboreal, and unidentified pollen grains. Subsum percent- interglacial warming ages on the left of the diagrams (Figs. 2–4) are calculated from a total of pollen and spores. Pollen zonation was done subjectively using changes in percentages of major A. V. Lozhkin and 10 taxa. Although many palynologists have differentiated tree and shrub Betula based on P. M. Anderson morphology and/or size, blind tests in our laboratories of modern reference materials suggest that these criteria are inconsistent and unreliable; thus we do no separate the Betula pollen. Picea obovata pollen is classified within Picea sect. Eupicea, Picea aja- Title Page nensis within Picea sect. Omorica, Pinus sylvestris within Pinus subg. Diploxylon, and Abstract Introduction 15 Pinus pumila and Pinus sibirica within Pinus subg. Haploxylon. Following traditional palynological usage, Duschekia fruticosa is referred to as shrub Alnus. All other plant Conclusions References taxonomy follows Cherepanov (1995). Tables Figures The age model for the El’gygytgyn record is based on paleomagnetic stratigraphy and tuning of additional proxy data to the marine isotope stratigraphy and to variations J I 20 in regional insolation (see Melles et al., 2012). Because pollen zones do not always correspond to isotope substages, the zones are identified by isotope stage (number) J I and as a pollen assemblage (letter). Following palynological format the lowest zone is indicated by “a” the next youngest by “b”, etc., in contrast to the order of isotope Back Close substages. Full Screen / Esc Printer-friendly Version Interactive Discussion 248 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 3 Modern setting CPD Lake E (67.5◦ N, 172◦ E; ∼ 500 m a.s.l.) has a diameter of ∼ 12 km and a maximum depth of 170 m (Melles et al., 2012). The local vegetation is a mix of discontinuous and 9, 245–267, 2013 continuous herb-lichen tundra (Kozhevnikov, 1993). Shrubs (Salix krylovii, S. alaxen- 5 sis, Betula exilis) are not abundant and limited to protected sites in valleys and saddles Vegetation within the crater walls and along the outlet valley. The vegetation in the Lake E catch- responses to ment is more barren than in the surrounding Chukchi Uplands, because of unusual interglacial warming soil qualities associated with the meteor impact crater. The Uplands are dominated by shrub tundra that includes Betula exilis, Duschekia fruticosa (shrub Alnus), Pinus A. V. Lozhkin and 10 pumila, Salix, and Ericales. Larix gmelinii treeline is located ∼ 150 to the southwest of P. M. Anderson the lake, but the main body of the forest is found at ∼ 300 km distance. Modern pollen studies indicate that the pollen rain in Lake E is more indicative of regional than lo- cal vegetation with up to 60 % of the pollen (Alnus, Betula,