Christian Overgaard Nielsen (January 16, 1918 - January 26, 1999) was a Danish

Denmark

Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...

 zoologist and ecologist.

Career

Overgaard Nielsen was a soil ecologist. He was a specialist on soil nematode

Nematode

The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...

s and Enchytraeidae

Enchytraeidae

The Enchytraeidae are a microdrile oligochaete family. They resemble small earthworms and include both terrestrial species known as potworms that live in highly organic terrestrial environments, as well as some that are marine...

. He investigated the role of the soil microfauna in the decomposition

Decomposition

Decomposition is the process by which organic material is broken down into simpler forms of matter. The process is essential for recycling the finite matter that occupies physical space in the biome. Bodies of living organisms begin to decompose shortly after death...

 of plant litter and recycling of nutrient

Nutrient

A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...

s in ecosystem

Ecosystem

An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

s.
He was a visiting scientist with Charles Elton

Charles Elton

Charles Elton may refer to:* Charles Isaac Elton , English lawyer, politician, writer and antiquarian* Charles Sutherland Elton , English biologist* Charles Elton , Chief of Police in Los Angeles, California...

 at Oxford University 1950-1953. He was then employed at the Mols Laboratory under Aarhus University. In 1964, he was appointed professor of zoology

Zoology

Zoology |zoölogy]]), is the branch of biology that relates to the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct...

 at the University of Copenhagen

University of Copenhagen

The University of Copenhagen is the oldest and largest university and research institution in Denmark. Founded in 1479, it has more than 37,000 students, the majority of whom are female , and more than 7,000 employees. The university has several campuses located in and around Copenhagen, with the...

.

He was the first Editor-in-Chief of the scientific journal Oikos

Oikos (journal)

Oikos is an international scientific journal published monthly by the Nordic Society Oikos in the field of ecology. It was previously known as Acta Oecologica Scandinavica....

(1949-1965).