Danish botanist and ecologist. Christen Raunkiaer succeeded the pioneering ecologist E. Warming as professor of botany and director of the Botanical Garden of Copenhagen (1912-1923). His name is most associated with the Raunkiaer life form system of categorising plants, which he devised in the 1900s.

Born in Varde, West Jutland, Raunkiaer developed a love of nature, especially plants, as a shepherd boy. Indeed he took his surname from the farm on which he grew up, having been originally named Christen Christiansen. He studied botany, graduating from the University of Copenhagen in 1885, after which he taught at Borchs Botanical College (1885-1888).

Before taking up a position as scientific assistant at the Copenhagen Botanical Garden and Botanical Museum in 1893, he travelled in Denmark and the Netherlands and produced his first important publications in 1888-1889. At this time he also embarked on a major work on Danish plants, De Danske Blomsterplanters Naturhistorie.

In 1898 he built a house near Jonstrup Vang and here laid the foundations of his most famous work, the life forms system, by studying plant life forms and their statistics throughout the year. The Raunkiaer life form system categorises plants according to the position of their perennating (over-wintering) buds in relation to the soil surface. For example, plants in cold areas such as the tundra generally have their buds protected below ground, while in tropical areas they are freely exposed. Raunkiaer first proposed this scheme of categorisation in 1904 and published it fully in 1907. Immediately seized upon by Scandinavian botanists and ecologists, it was not translated into English until 1934, when his collected works appeared under the title The Life Forms of Plants and Statistical Plant Geography (edited by Frank N. Egerton), bringing his ideas to an even wider scientific audience. His life forms, frequency analyses, and contemplations on species abundance distributions are still cited in most modern text books on ecology and biogeography.

Prior to the publication of his life forms system, in 1905-1906 Raunkiaer made a trip to the Danish West Indies (St. Croix, St. Thomas and St. John), where he collected plants. He also collected in Italy, North Africa, Spain and France over the years 1909-1910.

On the retirement of Eugene Warming in 1911, Raunkiaer was appointed professor of botany and director of the botanic garden at Copenhagen. He retired some 12 years later due to illness affecting his lungs and other problems, but continued to publish on subjects varying from the phyllotaxy of spruce cones to the number of plants mentioned in the works of two Danish poets. He strongly believed that science was comparable to poetry in that both depended on numerical patterns. In all he produced nearly 100 publications, largely on the flora of Denmark.

Sources:
P. Acevedo-Rodríguez et al, 1996, "Flora of St. John, U.S. Virgin Islands", Memoirs of the New York Botanical Garden, 78: 11
H. Gilbert-Carter, 1941, Proceedings of the Linnean Society, 151: 248-251
W.G. Smith, "Raunkiaer's 1913, 'Life-Forms' and Statistical Methods", Journal of Ecology, 1(1): 16.