A Last Glacial Maximum pollen record from Bodmin Moor showing a possible cryptic northern refugium in southwest England

Abstract

A Late Devensian palynological record is presented from Dozmary Pool (Bodmin Moor, southwest England), beyond the southern limit of the Last Glacial Maximum (LGM) British ice sheet. The pollen assemblages indicate predominantly herbaceous tundra-steppe communities but also include elevated levels (typically 10-20%) of conifer tree pollen (Picea, Pinus, Abies) and lower but persistent percentages of broadleaf tree pollen during the LGM. This record is seemingly at odds with the orthodox view of an entirely tree-less tundra-steppe environment for this region and elimination of tree species from the British Isles during glacial maxima. Long distance pollen transport seems an unlikely explanation for the tree pollen considering distance to the nearest known refugia, except possibly for Pinus. Reworking of the tree pollen, often invoked in these circumstances, remains a possible alternative, especially given the abundance of these trees in the region during early Devensian interstadials. However, this explanation has been challenged by studies reporting plant macrofossil and faunal evidence for survival of temperate biota during glacial maxima and from climate modelling work that suggests some trees could have survived the glacial extremes in areas well beyond the recorded glacial refugia. Assuming reworking was not a major factor, the Dozmary Pool pollen record is consistent with the 'cryptic northern refugia hypothesis' that invokes survival of trees in small, scattered populations under locally favourable conditions during glacial maxima.

Large Scale Anthropogenic Reduction of Forest Cover in Last Glacial Maximum Europe

“…In most of the rest of Europe, we reconstruct a mixture of steppe and open woodland. Our analysis further shows some sites close to the ice sheet edge with evidence of relatively high levels of arboreal taxa, suggesting pockets of woodland were able to survive in sheltered areas [80]. The possibility that the presence of arboreal taxa is the result of long distance transport or reworking is considered unlikely given the relatively high levels of arboreal pollen involved, and direct supporting evidence based on macrofossils [3, 81].…”

Modelling the Holocene migrational dynamics of Fagus sylvatica L. and Picea abies (L.) H. Karst

“…Kot et al, 1996;Clark, 1998), DNA-based analyses (Magri et al, 2006), and studies that assumed the existence of 'cryptic' northern refugia (e.g. Kelly et al, 2010) based on limited (e.g. Parducci et al, 2012) or even no pollen records (e.g.…”

Solving a conundrum of a steady-state hilltop with variable soil depths and production rates, Bodmin Moor, UK

“…Grasses currently dominate the vegetation at the site, but hazel and oak woodland likely blanketed Bodmin Moor during the early Holocene (Gearey et al, 2000). During the last glacial maximum, Bodmin Moor was dominated by herbaceous tundra-steppe, but may have had isolated pockets of conifer (Picea, Pinus, and Abies) and broadleaf trees in favorable refugia (Kelly et al, 2010).…”