A pollen-based biome reconstruction over the last 3.562 million years in the Far East Russian Arctic – new insights into climate–vegetation relationships at the regional scale

摘要

The recent and fossil pollen data obtained under the frame of themulti-disciplinary international El'gygytgyn Drilling Project representa unique archive, which allows the testing of a range of pollen-basedreconstruction approaches and the deciphering of changes in the regionalvegetation and climate. In the current studywe provide details of the biome reconstruction method applied to the latePliocene and Quaternary pollen records from Lake El'gygytgyn. Allterrestrial pollen taxa identified in the spectra from Lake El'gygytgyn wereassigned to major vegetation types (biomes), which today occur near the lakeand in the broader region of eastern and northern Asia and, thus, could bepotentially present in this region during the past. When applied to thepollen spectra from the middle Pleistocene to present, the method suggests(1) a predominance of tundra during the Holocene, (2) a short intervalduring the marine isotope stage (MIS) 5.5 interglacial distinguished by colddeciduous forest, and (3) long phases of taiga dominance during MIS 31 and,particularly, MIS 11.3. These two latter interglacials seem to be some ofthe longest and warmest intervals in the study region within the pastmillion years.During the late Pliocene–early Pleistocene interval (i.e., ~3.562–2.200 Ma),there is good correspondence between the millennial-scalevegetation changes documented in the Lake El'gygytgyn record and thealternation of cold and warm marine isotope stages, which reflect changes inthe global ice volume and sea level. The biome reconstruction demonstrateschanges in the regional vegetation from generally warmer/wetter environmentsof the earlier (i.e., Pliocene) interval towards colder/drier environmentsof the Pleistocene. The reconstruction indicates that the taxon-rich coolmixed and cool conifer forest biomes are mostly characteristic of the timeprior to MIS G16, whereas the tundra biome becomes a prominent featurestarting from MIS G6. These results consistently indicate that the study region supportedsignificant tree populations during most of the interval prior to~2.730 Ma. The cold- and drought-tolerant steppe biome firstappears in the reconstruction ~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. Priorto ~2.800 Ma, several other cold stages during this generallywarm Pliocene interval were characterized by the tundra biome.