scholarly journals Lateglacial and Holocene floras and faunas from the Salpetermosen area, north-east Sjælland, Denmark

2020 ◽  
Vol 68 ◽  
pp. 231-244
Author(s):  
Ole Bennike ◽  
Pernille Pantmann ◽  
Esben Aarsleff
Keyword(s):  
Alnus Glutinosa ◽  
Betula Pubescens ◽  
Populus Tremula ◽  
Betula Nana ◽  
Najas Marina ◽  
North East ◽  
Glacier Ice ◽  
Dwarf Birch ◽  
Scheuchzeria Palustris ◽  
Oenanthe Aquatica

The Salpetermosen area in north-east Sjælland, Denmark, was deglaciated about 18 000 to 17 000 years ago. Melting of bodies of stagnant glacier ice led to the for-mation of kettle holes, which contain Lateglacial and Holocene sediments with remains of plants and animals that provide information on the past flora and fauna of the area. During the Allerød period, open forests with Betula pubescens (downy birch) characterised the area, the flora included light-demanding species such as Arctostaphylos uva-ursi (bearberry), Empetrum nigrum (crowberry) and rare Populus tremula (aspen), Betula nana (dwarf birch) and Rubus saxatilis (stone bramble), as well as the thermophilous swamp plant Oenanthe aquatica (fine-leaved water dropwort). During the Younger Dryas, the vegetation was characterised by dwarf-shrub heaths dominated by Betula nana, but including Dryas octopetala (mountain avens), Salix herbacea (least willow), Arctostaphylos alpina (alpine bearberry,) and rare Betula pube-scens, as well as the thermophilous plants Urtica dioeca (stinging nettle) and Lychnis flos-cuculi (ragged robin). The Early Holocene forests were dominated by Betula pubescens, Populus tremula and Pinus sylvestris (scots pine), but included rare Betula nana. Alnus glutinosa (alder) arrived at c. 10 000 cal. years BP. The calciphilous sedge Cladium mariscus (fen-sedge) and the macrolimnophyte Najas marina (spiny naiad) were common. The Late Holocene flora included the acidophilous plant Scheuchzeria palustris (rannoch-rush).

Demographic variation of dwarf birch (Betula nana) in communities dominated by Ledum palustre and Vaccinium uliginosum

Biologia ◽  
2010 ◽  
Vol 65 (2) ◽  
Author(s):  
Wojciech Ejankowski
Keyword(s):  
Population Growth ◽  
Sexual Reproduction ◽  
Vegetative Growth ◽  
Light Limitation ◽  
Permanent Plots ◽  
Peat Bogs ◽  
Betula Nana ◽  
Vaccinium Uliginosum ◽  
Ledum Palustre ◽  
Dwarf Birch

AbstractThe structure and demographic processes were compared in shrub communities to test the effects of vegetation succession on population growth, fecundity and abundance of the dwarf birch (Betula nana L.), which is a rare and endangered plant species in Poland and a glacial relict in Central Europe. The effects of Ledum palustre L. and Vaccinium uliginosum L. were studied in the Linje nature reserve in Chełmińskie Lake District (northern Poland), in three permanent plots on a peat bog. Vegetative growth and reproduction of B. nana were lower in plant communities dominated by L. palustre and V. uliginosum, than in a reference site. Fecundity was also lower, despite the fact that the percentage share of potentially fertile age groups was similar in all study sites. Mortality of ramets was independent of vegetation, both for juvenile and mature stages. The results confirm that B. nana is intolerant of shade, and it is more abundant in vegetation without competitors. Light limitation can lead to its decline, primarily by a decrease in vegetative growth. Sexual reproduction may be negatively affected by shade, but it plays only small role in population growth. Butterfly larvae can destroy inflorescences, and thus contribute to low effectiveness of sexual reproduction. Increasing density of shrubs and trees in peat bogs can reduce the abundance of dwarf birch, and can lead to the extinction of its local populations.

scholarly journals Measurement of the Fracture Toughness of Glacier Ice

1985 ◽  
Vol 31 (108) ◽  
pp. 171-176 ◽  
Author(s):  
R.M. Andrews
Keyword(s):  
Fracture Toughness ◽  
Laboratory Tests ◽  
Testing Material ◽  
East Greenland ◽  
North East ◽  
Pressure Tests ◽  
Valley Glacier ◽  
Glacier Ice ◽  
Toughness Testing ◽  
Alternative Specimen

AbstractFracture-toughness testing of both fresh-water and sea ice has used specimen geometries designed for metals. These designs are too large and difficult to manufacture for testing material cored from a glacier. This paper presents an alternative specimen, a radially cracked ring fractured by internal pressure. Tests using this specimen on the Bersærkerbræ, a valley glacier in the Stauning Alper, north-east Greenland, gave a mean fracture toughness of 58 . This is half the value typically obtained by other workers in laboratory tests. The results are compared with other data and the reasons for the disagreement discussed.

scholarly journals Measurement of the Fracture Toughness of Glacier Ice

1985 ◽  
Vol 31 (108) ◽  
pp. 171-176 ◽  
Author(s):  
R.M. Andrews
Keyword(s):  
Fracture Toughness ◽  
Laboratory Tests ◽  
Testing Material ◽  
East Greenland ◽  
North East ◽  
Pressure Tests ◽  
Valley Glacier ◽  
Glacier Ice ◽  
Toughness Testing ◽  
Alternative Specimen

AbstractFracture-toughness testing of both fresh-water and sea ice has used specimen geometries designed for metals. These designs are too large and difficult to manufacture for testing material cored from a glacier. This paper presents an alternative specimen, a radially cracked ring fractured by internal pressure. Tests using this specimen on the Bersærkerbræ, a valley glacier in the Stauning Alper, north-east Greenland, gave a mean fracture toughness of 58. This is half the value typically obtained by other workers in laboratory tests. The results are compared with other data and the reasons for the disagreement discussed.

The vegetation of North Fen at Esthwaite in 1967-9

1978 ◽  
Vol 200 (1140) ◽  
pp. 331-351 ◽  
Keyword(s):  
Open Water ◽  
Alnus Glutinosa ◽  
Quercus Petraea ◽  
Betula Pubescens ◽  
Ordnance Survey ◽  
The North ◽  
Order Of Magnitude ◽  
Carex Rostrata ◽  
Southward Extension ◽  
Rate Of Movement

The vegetation of part of the fen at the north end of Esthwaite Water (2° 59' W 54° 22' N) has been surveyed three times: in 1914-16, 1929 and 1967-9. The maps provide direct evidence of vegetational succession. The main associations have retained their identity throughout the period of half a century but the reed-swamp has advanced southward into open water and been replaced along its landward edge by fen dominated by Carex rostrata . Comparing the position of this boundary with that of the shore on the Ordnance Survey of 1848, the southward movement has been 47 m at the mouth of the inflow stream and 28 m in the middle of the basin. Comparing all the surveys it is clear that the rate of movement has varied from one period to another by an order of magnitude (0.2- 3.0 m/a). The most prominent change since 1929 has been the southward extension of woodland of Alnus glutinosa and Salix cinerea on the alluvial part of the fen, the recent spread of Betula pubescens and Farxinus excelsior and gradual extension of Alnus glutinosa into the sedge-fen. A few saplings of Quercus petraea are now established beneath dying trees of Betula pubescens in the oldest part of the carr. Analytical and experimental evidence suggest that the vegetation may also be changing in response to an increased input of phosphate and nitrate.

scholarly journals A multi-disciplinary macrofossil study of late glacial to early Holocene sediments from Søndre Kobberdam, Hareskovene, Denmark

2018 ◽  
Vol 66 ◽  
pp. 113-122 ◽  
Author(s):  
Ole Bennike ◽  
Morten Fischer Mortensen
Keyword(s):  
Pinus Sylvestris ◽  
Younger Dryas ◽  
Late Glacial ◽  
Betula Pubescens ◽  
Betula Nana ◽  
The Holocene ◽  
Dryas Octopetala ◽  
Holocene Sediments ◽  
Carex Riparia

During the early part of the Allerød period, from c. 13 600 to 13 330 years BP, unstable soils with a tundra-like open, treeless vegetation with Betula nana and Dryas octopetala were found around Søndre Kobberdam in Hareskovene. Open Betula pubescens woodland was not established until the middle Allerød about 13 330 years BP. During the Younger Dryas, Betula nana and Dryas octopetala spread again, and Betula pubescens almost disappeared. From the onset of the Holocene warming an open tundra landscape characterised the area. About 11 300 years BP Betula pubescens started to recolonise the region and Populus tremula and Pinus sylvetris arrived at c. 11 000 years BP, replacing the open landscape by woodland. Along the margin of the lake Carex paniculata, Carex riparia and Cladium mariscus were growing. The lake fauna included a rich and diverse fauna of molluscs that thrived in the carbonate-rich waters. We did not find any evidence for the local presence of Pinus sylvestris during the late glacial.

Decreased phenolic defence in dwarf birch (Betula nana) after warming in subarctic tundra

Polar Biology ◽  
2015 ◽  
Vol 38 (12) ◽  
pp. 1993-2005 ◽  
Author(s):  
S. Stark ◽  
M. Väisänen ◽  
H. Ylänne ◽  
R. Julkunen-Tiitto ◽  
F. Martz
Keyword(s):  
Betula Nana ◽  
Dwarf Birch
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