The Lateglacial and early Holocene vegetation and environment in the Dovre mountains,central Norway,as signalled in two Lateglacial nunatak lakes |
| |
| Authors: | Aage Paus Gaute Velle Jan Berge |
| |
| Institution: | 1. Department of Physical Geography and the Bolin Centre for Climate Research, Stockholm University, 106 91 Stockholm, Sweden;2. Department of Ecology and Environmental Sciences, Umeå University, 901 87 Umeå, Sweden;3. Department of Geological Sciences and the Bolin Centre for Climate Research, Stockholm University, 10691 Stockholm, Sweden;4. Department of Geosciences, National Taiwan University, P.O. Box 13-318, Taipei, Taiwan;5. Department of Geosciences and Geography, P.O. Box 64, University of Helsinki, 00014, Finland;6. Department of Environmental Sciences, P.O. Box 65, University of Helsinki, 00014, Finland;1. State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, 100875 Beijing, China;2. Key Laboratory of Plateau Geographical Process and Environmental Change of Yunnan Province, School of Tourism and Geographical Sciences, Yunnan Normal University, Kunming 650500, China |
| |
| Abstract: | By using heavy coring equipment in two high-altitudinal lakes (1253 and 1316 m a.s.l.) at Dovre, Central Norway, 1–1.5 m of unsorted coarsely minerogenic sediments were retrieved below the Holocene organic sediments. The minerogenic sequence contained well-preserved pollen and chironomid remains, revealing new and detailed palaeoenvironmental knowledge of the mountains in Central Norway during the last 5–6000 years of the Lateglacial (LG) period. However, the LG chronology is based on biostratigraphical correlations and not on 14C-dates, due to low organic content in the minerogenic sediments. The emerging LG nunataks, probably indicating a thin and multi-domed Scandinavian ice-sheet, was rapidly inhabited by immigrating species which could explain the present centric distributions of certain arctic-alpine plants. The LG vegetation development included a pre-interstadial dominated by mineral-soil pioneers, an interstadial dominated by shrubs and dwarf-shrubs, and the Younger Dryas cold period with recurring dominance of pioneers. Pollen and stomata of Pinus and Picea indicate their local LG presence at Dovre. LG climate oscillations are indicated by pollen stratigraphy and for the later part of LG also by chironomids. These oscillations could correspond to Heinrich event 1, GI-1d, GI-1b, and the Younger Dryas cold events. The LG interstadial reached July mean temperatures of more than 7–8 °C, similar to the present. Chironomids colonized the lake already during the onset of the interstadial, albeit at very low richness and abundances. Starting from YD, there are sufficient chironomid head capsules to perform a temperature reconstruction. The Holocene warming of about 2 °C initiated a vegetation closure from snow beds and dwarf-shrub tundra to shrubs and forests. Birch-forests established about 10 ka cal BP, slightly earlier than pine forests. Alnus expanded ca 9.2 ka cal BP and a thinning of the local forests occurred from ca 7 ka cal BP. Two short-lasting climate deteriorations found in the pollen record and the chironomid record may represent the Preboreal Oscillation and the 8.2 event. The Holocene Thermal Maximum is indicated around ca 7.8–7.3 ka cal BP showing a chironomid-inferred July mean of at least 11 °C. This is ca 3 °C warmer than today. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
