Affiliation:
1. Department of Quaternary Geology, Lund University, Tornavägen 13, S-223 63 Lund, Sweden
Abstract
Lake-sediment records of pollen and macroscopic plant remains of terrestrial origin provide evidence of long-term changes in forest composition close to the altitudinal tree-line in the Abisko area, northernmost Sweden. A dominance of mountain birch ( Betula pubescens Ehrh. ssp. tortuosa (Ledeb.) Nyman) with a field layer of ferns, grasses and sedges suggests that an oceanic climate with relatively high precipitation existed during the early Holocene. Macrofossils of mountain birch were found 300–400 m above the present tree-line which corresponds to a 1.5–2°C higher summer temperature than at present. Scots Pine ( Pinus sylvestris) was present to some extent at altitudes above its present limit during the early Holocene. A pronounced expansion of pine took place above its present limit around 6300 cal. BP (5500 BP). This is interpreted as a result of successively drier and more continental climatic conditions. A decreased abundance of pine from c. 5200 cal. BP (4700 BP), followed by a gradual retraction of the upper limit of pine during the later part of the Holocene, can be attributed mainly to long-term changes in solar radiation. A decline in the upper limit of pine of c. 175 m since 4500 cal. BP (4000 BP) is believed to represent a decrease in growing-season temperature of c. 1.5°C.
Subject
Paleontology,Earth-Surface Processes,Ecology,Archeology,Global and Planetary Change
Cited by
138 articles.
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