The biome reconstruction approach as a tool for interpretation of past vegetation and climate changes: application to modern and fossil pollen data from Lake El'gygytgyn, Far East Russian Arctic

Abstract

Abstract. The modern and fossil pollen data obtained under the framework of the multi-disciplinary international "El'gygytgyn Drilling Project" represent a unique archive that allows the testing of a range of pollen-based reconstruction approaches and the deciphering of changes in the regional vegetation and climate since ~3.58 Ma. In the current study we provide details of the biome reconstruction method applied to the late Pliocene and Quaternary pollen records from Lake El'gygytgyn. All terrestrial pollen taxa identified in the spectra from Lake El'gygytgyn were assigned to major vegetation types (biomes), which today occur near the lake and in the broader region of eastern and northern Asia and, thus, could potentially have been present in this region during the past. When applied to the modern surface pollen spectra from the lake, the method shows a dominance of the tundra biome that currently characterizes the Lake El'gygytgyn area. When applied to the pollen spectra from the middle Pleistocene to present, the method suggests (1) a predominance of tundra during the Holocene, (2) a short interval during the marine isotope stage (MIS) 5.5 interglacial distinguished by cold deciduous forest, and (3) a long phase of taiga dominance during MIS 31 and, particularly, MIS 11.3. These two latter interglacials seem to be some of the longest and warmest intervals within the past million years. During the late Pliocene–early Pleistocene interval (i.e., ~3.562–2.200 Ma), there is good correspondence between the millennial-scale vegetation changes documented in the Lake El'gygytgyn record and the alternation of cold and warm marine isotope stages, which reflect changes in the global ice volume and sea level. The biome reconstruction demonstrates changes in the regional vegetation which suggest a step-like transition from generally warmer/wetter environments of the earlier (i.e., Pliocene) interval towards colder/drier environments of the Pleistocene. The reconstruction of most of the species-rich cool mixed and cool conifer forest biomes is particularly noticeable prior to MIS G16, whereas tundra becomes a prominent feature after MIS G6. These results consistently indicate that the study region supported significant tree populations during most of the interval prior to ~2.730 Ma. The biomization results also suggest that the transition from mostly forested to mostly open landscape was not gradual, but rather occurred in step-like fashion. Thus, the cold and drought tolerant steppe biome first appears in the reconstruction ca. 3.298 Ma during the tundra dominated MIS M2, whereas the tundra biome initially occurs between ~3.379 and ~3.378 Ma within MIS MG4. Prior to ~2.800 Ma, several other cold stages during this generally warm Pliocene interval experienced a dominance of tundra and a great reduction of tree populations in the regional vegetation.