Limiting factors for vegetation development during the early late glacial in Denmark

• Main Authors: Mortensen, Morten Fischer, Odgaard, Bent Vad, Jessen, Cathrine
• Format: Conference Object
• Language: English
• Published: 2011
• Subjects: Betula nana; Dryas octopetala; ice core; NGRIP
• Online Access: https://pure.au.dk/portal/da/publications/limiting-factors-for-vegetation-development-during-the-early-late-glacial-in-denmark(90ce76f2-d360-4f10-ab81-bd53944d4db5).html

Slotseng, a small basin in southern Jutland, is the first Danish site with a bio- and chronostratigraphy that unambiguously reflects the environment of the earliest late glacial, the Bølling period. Results of pollen and macrofossil analyses show that the vegetation of the Bølling and Older Dryas periods at Slotseng was dominated by Betula nana and Dryas octopetala and associated with many herbs of open habitats. Late-glacial pollen records are frequently interpreted only in the context of climate change. However, the forcing mechanisms of vegetational change may shift over time between e.g. climate change, soil erosion or soil development. In an attempt to identify the most important factors determining the temporal variation of the pollen record at Slotseng, redundancy analysis (RDA) was applied to subsets of pollen data representing a moving window of 20 samples at a time (1-20, 2-21, 3-22, etc.). Sediment age was used as a covariable and explanatory variables representing environmental change were soil nitrogen, R, and light (all inferred from the Ellenberg indices estimated from macrofossil results), LOI, SUS, sediment accumulation rate, presence of tree-birch macrofossils, sediment type (peat/gyttja) and δ18O from assumedly synchronous levels in the NGRIP and GRIP ice-cores. Our series of RDA’s show that climate variations as expressed by proxy ice-core δ18O had limited correlation with our pollen data during these shorter intervals. The lack of immediate palynological response to climate change suggests that other factors limited vegetational development. These factors included soil instability, aridity and low soil nitrogen. This study highlights the multitude of climatic, physical, chemical and biological interactions important for the formation of pollen records of late glacial vegetation changes. This result strongly suggests that late glacial pollen records may not be interpreted merely as a direct climate proxy.