Читать книгу Biogeography in the Sub-Arctic - Группа авторов - Страница 60

Analyses of samples from core ODP 646 indicate that marine oxygen isotope stage 11 was characterized by a much reduced, nearly vanished Greenland ice sheet, with boreal coniferous forest with abundant Picea and some Abies in southern Greenland (de Vernal and Hillaire‐Marcel 2008). The MIS 11 interglacial is different from other Middle Quaternary interglacials because of its near 50 000‐year duration. It is dated to ~400 ka. The dominance of Picea from the beginning to the end of the interglacial period suggests the presence of forest vegetation throughout the entire interval, at least over southern Greenland. The base of MIS 11 is marked by higher proportions of shrub and herb pollen, indicating more open vegetation and a cooler climate, but Picea was probably already present regionally. Detailed examination of the Picea pollen indicates the occurrence of several species, among which Picea abies dominated. Picea abies is presently common in northern Europe.

Studies of the basal silty‐rich ice from the 2 km long DYE‐3 ice core from south‐central Greenland showed that the ice contains remains of DNA molecules that could be assigned to Picea, Pinus, Alnus, Taxaceae, Poaceae, Asteraceae and Fabaceae. The presence of these plant taxa indicates open northern boreal forests, very different from today's Arctic environment (Willerslev et al. 2007). These taxa were identified by independent laboratories; in addition, Achillea, Betula, Cerastium, Festuca, Luzula, Plantago, Poa, Saxifraga, Symphoricarpos and Populus were recorded but lacked identity between independent laboratories. Most of these genera are common in northern boreal forests. The ice also contained arthropod DNA from Lepidoptera and probably Coleoptera, Diptera, Arachnida and Nymphalidae. The age of the DNA molecules from DYE‐3 is uncertain, but it is possible that they correlate with marine oxygen isotope stage 11.