Thorvald Julius Sørensen
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| Born | (1902-07-04)4 July 1902
Sækbæk, Denmark
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| Died | 21 June 1973(1973-06-21) (aged 70) |
| Nationality | Danish |
| Alma mater | University of Copenhagen |
| Known for | Flora of the Arctic, Sørensen similarity index |
| Scientific career | |
| Fields | Botany |
| Institutions | University of Copenhagen |
Thorvald (Thorwald) Julius Sørensen (4 July 1902 – 21 June 1973) was a Danish botanist and evolutionary biologist. [1]
Sørensen was professor at the Royal Veterinary and Agricultural University 1953–1955 and at the University of Copenhagen 1955–1972. He was director of the Copenhagen Botanical Garden and Botanical Museum during the same period.[1]
Thorvald Sørensen spent the years 1931–1935, based on Ella Island, studying plants in the then little known North-East Greenland. He published the botanical research of the Three-year Expedition to East Greenland.[2] He also published a doctoral thesis on the annual phenological rhythm of the High Arctic plant species, including the pollination of their flowers (1941).
He critically revised the Greenland flora and sorted out taxonomy of a number of difficult taxa, most notably Puccinellia.
He carried out a number of studies in the evolutionary biology of plants, such as Taraxacum, Capsella bursa-pastoris 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 grasslandbyJohannes Grøntved (1882-1956), who used the quantitative method to sample vegetation developed by Christen C. Raunkiær (1860–1938).[3] [4]
The Arctic campion species Silene sorensenis and Th. Sørensen Land in Greenland were named in his honour.
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