Америкалық өсімдік экологы Фредерик Эдвард Клементс

American plant ecologist

Frederic Edward Clements (September 16, 1874 – July 26, 1945) was an American plant ecologist and pioneer in the study of plant ecology and vegetation succession.

Born in Lincoln, Nebraska, he studied botany at the University of Nebraska, graduating in 1894 and obtaining a doctorate in 1898. One of his teachers was botanist Charles Bessey, who inspired Clements to research topics such as microscopy, plant physiology, and laboratory experimentation. He was also classmate of Willa Cather and Roscoe Pound. While at the University of Nebraska, he met Edith Gertrude Schwartz (1874–1971), also a botanist and ecologist, and they were married in 1899. In 1905 he was appointed full professor at the University of Nebraska, but left in 1907 to head the botany department at the University of Minnesota in Minneapolis. From 1917 to 1941 he was employed as an ecologist at the Carnegie Institution of Washington in Washington, D. C., where he was able to carry out dedicated ecological research. a research station in Englemann Canyon on the slopes of Pikes Peak, Colorado. During this time he worked alongside staff of the U. S. Soil Conservation Service. In addition to his field investigations, he carried out experimental work in the laboratory and greenhouse, both at the Pikes Peak station and at Santa Barbara.

From his observations of the vegetation of Nebraska and the western United States, Clements developed one of the most influential theories of vegetation development. Vegetation composition does not represent a permanent condition but gradually changes with time. Clements suggested that the development of vegetation can be understood as a unidirectional sequence of stages resembling the development of an individual organism. After a complete or partial disturbance, vegetation grows back (under ideal conditions) towards a stable "climax state", which describes the vegetation best suited to the local conditions. Though any actual instance of vegetation might follow the ideal sequence towards stability, it can be interpreted in relation to that sequence, as a deviation from it due to non ideal conditions. In these studies, he and Roscoe Pound (who subsequently moved from ecology to legal scholarship) developed the widely used method of sampling using quadrats around 1898. Clements's climax theory of vegetation dominated plant ecology during the first decades of the twentieth century, though it was criticized significantly by ecologists William Skinner Cooper, Henry Gleason and Arthur Tansley early on, and by Robert Whittaker mid century, and largely fell out of favor. He observed that some groups of species, which he called "formations", were repeatedly associated together. Clements observed little overlap in kinds of species from type to type, with many species confined to just a single type.

Clements was an advocate of neo Lamarckian evolution. Ecologist Arthur Tansley wrote that because of his support for Lamarckism, Clements "never seemed to give proper weight to the results of modern genetical research." Science historian Ronald C. Tobey has commented that:

[Clements] believed that plants and animals could acquire a wide variety and range of characteristics in their struggle to survive and adapt to their environment, and that these features were heritable. In the 1920s, he conducted experiments to transform plant species native to one ecological zone into a species adapted to another, higher, zone. Clements was quite convinced of the validity of his experiments, but this experimental Lamarckism fell to experimental disproof in the 1930s. Clements spent much time trying to demonstrate the inheritance of acquired traits in plants. By the late 1930s scientists had provided
Darwinian explanations for the results of his transplant experiments.

In 1903, the flower Clementsia rhodantha Rhodiola rhodantha ("Clements's rose flower"), a stonecrop, was named in honor of Frederic Clements.