Boreal tree taxa in the central Scandes during the Late‐Glacial: implications for Late‐Quaternary forest history

Abstract

Aim This paper seeks to elucidate the first post‐glacial arrival of tree species to high elevations in the Scandes. This enables testing of general theories concerning glacial refugia, immigration routes and palaeoclimate. Location The study site, 1360 m a.s.l., was close to the summit of Mt Åreskutan in the alpine region of the southern Swedish Scandes, 400–500 m above modern tree‐limits. Methods Tree megafossils (trunks, roots, cones) were retrieved (and radiocarbon‐dated) from the ground surface in the forefields of receding `perennial' snow‐patches. This approach allows elevational range‐margin reconstructions to be made with an accuracy not possible with any other method. Results and conclusions Megafossils were recovered substantially higher and earlier than previously recorded or inferred for tree growth in this part of Europe. The species were Betula pubescens Ehrh. ssp. tortuosa (Ledeb.) Nyman, Picea abies (L.) Karst. and Pinus sylvestris (L.). The oldest dates obtained are c. 14,000, 11,000 and 11,700 BP for these species, respectively. For the first time, explicit evidence of tree growth in the Late‐Glacial (including the Younger Dryas stadial) is demonstrated for central/northern Scandinavia. The swift appearance of boreal tree species at high northern latitudes and altitudes on the western fringe of Scandinavia and near the most extended margin of the Weichselian ice sheet hypothetically suggests that the first immigration of the trees considered here was from the west. Glacial refugia for these species (other plants and animals as well) on the exposed continental shelf areas west and southwest of Norway is hypothesized. By extension, the results fit into a more general pattern, suggesting the presence of boreal and temperate trees quite close to the full glacial (Weichselian) ice margins in central Europe. Thus, the Quaternary forest and landscape history of Europe seems more complex than previously believed.

Further Details on Holocene Treeline, Glacier/Ice Patch and Climate History in Swedish Lapland

“…This pattern is compatible with an earlier inference, based onmegafossil performance, that trees (and possibly other plant species, have in general spread downslope from primary"occurrence sites" at high elevations, e.g. empty glacier cirques (Kullman 2002). …”

The importance of plant macrofossils in the reconstruction of Lateglacial vegetation and climate: examples from Scotland, western Norway, and Minnesota, USA

“…Temperatures only exceeded the birch thermal limit at the start of the Holocene and it then spread rapidly. All the available evidence contradicts the assumption made by Kullman (2002) of temperatures high enough for the full-and Lateglacial survival of tree-Betula, Pinus, and Picea along or near the Norwegian west coast as there is a total lack of direct macrofossil evidence for such tree growth and local vegetation (and climate) reconstructions from macrofossils are analogous to those above or beyond treeline today.…”

Glacial survival of trophically linked boreal species in northern Europe

“…A recent debate has emerged in the literature, from available evidences for the presence of other boreal plant species in western Norway during the last glaciation (e.g. [60][61][62]). Evidence for the presence of S. aucuparia in northern Europe is available at least for the late glacial period (e.g.…”