Thorvald (Thorwald) Julius Sørensen (4 July 1902 – 21 June 1973) was a Danish botanist and

evolutionary biologist Evolutionary biology is the subfield of biology that studies the evolutionary processes (natural selection, common descent, speciation) that produced the diversity of life on Earth. It is also defined as the study of the history of life for ...

Biography

Sørensen was professor at the Royal Veterinary and Agricultural University 1953–1955 and at the

University of Copenhagen The University of Copenhagen ( da, Københavns Universitet, KU) is a prestigious public research university in Copenhagen, Denmark. Founded in 1479, the University of Copenhagen is the second-oldest university in Scandinavia after Uppsala Unive ...

1955–1972. He was director of the Copenhagen Botanical Garden and Botanical Museum during the same period. Thorvald Sørensen spent the years 1931–1935, based on

Ella Island Ella Island, or Ella Ø, is an island in eastern Greenland, within Northeast Greenland National Park. Geography Ella Island is located at the mouth of Kempe Fjord in the northern end of King Oscar Fjord. To the east lie larger Traill Island and ...

, studying plants in the then little known North-East

Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland i ...

. He published the botanical research of the

Three-year Expedition to East Greenland The Three-year Expedition ( da, Treårsekspeditionen) was an exploratory expedition to East Greenland that lasted from 1931 to 1934 financed by the Carlsberg Foundation and the Danish state. The expedition included aerial surveys. Many geograph ...

. He also published a doctoral thesis on the annual phenological rhythm of the High Arctic plant species, including the

pollination Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds, a ...

of their flowers (1941). He critically revised the

flora and sorted out

taxonomy Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

of a number of difficult

taxa In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

, most notably ''

Puccinellia ''Puccinellia'' is a genus of plants in the grass family, known as alkali grass or salt grass. These grasses grow in wet environments, often in saline or alkaline conditions. They are native to temperate to Arctic regions of the Northern and S ...

''. He carried out a number of studies in the

evolutionary biology Evolutionary biology is the subfield of biology that studies the evolutionary processes ( natural selection, common descent, speciation) that produced the diversity of life on Earth. It is also defined as the study of the history of life ...

of plants, such as ''

Taraxacum ''Taraxacum'' () is a large genus of flowering plants in the family Asteraceae, which consists of species commonly known as dandelions. The scientific and hobby study of the genus is known as taraxacology. The genus is native to Eurasia and Nor ...

'', ''

Capsella bursa-pastoris ''Capsella bursa-pastoris'', known as shepherd's purse because of its triangular flat fruits, which are purse-like, is a small annual and ruderal flowering plant in the mustard family (Brassicaceae). It is native to eastern Europe and Asia minor, ...

'' and '' Ranunculus''. He developed a quotient of similarity in species composition between plant communities—the still much-used Sørensen similarity index. He illustrated its use on a data set collected in Danish

grassland A grassland is an area where the vegetation is dominated by grasses ( Poaceae). However, sedge ( Cyperaceae) and rush ( Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur na ...

by Johannes Grøntved (1882-1956), who used the quantitative method to sample vegetation developed by

Christen C. Raunkiær Christen Christensen Raunkiær (29 March 1860 – 11 March 1938) was a Danish botanist, who was a pioneer of plant ecology. He is mainly remembered for his scheme of plant strategies to survive an unfavourable season ("life forms") and his demons ...

(1860–1938).

Selected plant names he published

*'' Braya intermedia'' T.J.Sørensen (1954) in

Meddelelser om Grønland ''Meddelelser om Grønland'' ("''Communications on Greenland''") is a Danish scientific periodical which publishes scientific results from all fields of research on Greenland. It was established by Frederik Johnstrup and published as a single seri ...

134 (8). *''

Puccinellia groenlandica ''Puccinellia'' is a genus of plants in the grass family, known as alkali grass or salt grass. These grasses grow in wet environments, often in saline or alkaline conditions. They are native to temperate to Arctic regions of the Northern and S ...

'' T.J.Sørensen (1953) in

134 (3).

Honours

The Arctic campion species '' Silene sorensenis'' and Th. Sørensen Land in Greenland were named in his honour.

Selected publications

*Sørensen, T. (1935) Bodenformen und Pflanzendecke in Nordostgrönland. Beiträge zur Theorie der polaren Bodenversetzungen auf Grund von Beobachtungen über deren Einfluss auf die Vegetation in Nordostgrönland.

93 (4). *Sørensen, T. (1941) Temperature relations and

phenology Phenology is the study of periodic events in biological life cycles and how these are influenced by seasonality, seasonal and interannual variations in climate, as well as environmental factor, habitat factors (such as elevation). Examples includ ...

of the Northeast

flowering plants.

129: 1–305. *Sørensen, T. (1942) Untersuchungen über die Therophytengesellschaften auf den isländischen Lehmflächen ("Flags"). Biologiske Skrifter /

Kongelige Danske Videnskabernes Selskab {{Infobox organization , name = The Royal Danish Academy of Sciences and Letters , full_name = , native_name = Det Kongelige Danske Videnskabernes Selskab , native_name_lang = , logo = Royal ...

2 (2). *Sørensen, T. and Gudjónsson, Gudni (1946) Spontaneous chromosome-aberrants in apomictic Taraxaca: morphological and cyto-genetical investigations. Biologiske Skrifter /

4 (2). *Sørensen, T. (1948) A method of establishing groups of equal amplitude in plant sociology based on similarity of species and its application to analyses of the vegetation on Danish commons. Biologiske Skrifter /

5: 1-34. *Sørensen, T. (1953) A Revision of the Greenland Species of ''

'' Parl. With contribution to our knowledge of the Arctic ''

'' flora in general.

136 (3) 1–179. *Jørgensen, C.A., Sørensen, T. and Westergaard, M. (1958) The Flowering Plants of Greenland. Biologiske Skrifter /

9 (4).

References

Other sources

*Obituary in

Botanisk Tidsskrift ''Botanisk Tidsskrift'' (standard abbreviation ''Bot. Tidsskr.'') was a Danish mixed scientific and amateur journal concerning botany, issued in Copenhagen by the Danish Botanical Society. It was published from 1866 to 1980, when it fused with Bot ...

68 (2): 165-168 (1973) {{DEFAULTSORT:Sorensen, Thorvald Botanists active in the Arctic 20th-century Danish botanists Danish ecologists Danish biologists University of Copenhagen alumni Academic staff of the University of Copenhagen 1902 births 1973 deaths