Knud Jessen
Encyclopedia
Knud Jessen was a Danish botanist and quaternary geologist.
He was state geologist 1917-1931. In 1931, he succeeded C.H. Ostenfeld
as professor of botany
at the University of Copenhagen
and director of the Copenhagen Botanical Garden, a position he held until his retirement in 1955. His scientific works mainly concern vegetation history during the Eemian interglacial
, the late glacial period of the Wisconsin glaciation
and in the Holocene
investigated using pollen analysis
.
Jessen had come into contact with the Irish
naturalist Robert Lloyd Praeger
and made field-work on the quaternary geology of Ireland
during 1934-1935. Together with his assistant, Frank Mitchell, he was able to describe both the post-glacial
vegetation development of Ireland
and that of the Eemian interglacial
, with the presence in Ireland
of such plants as Rhododendron ponticum
, Abies alba, Erica scoparia and Buxus sempervirens
.
Jessen was acknowledged by honorary doctorates at the University of Cambridge
and University of Dublin
. He was a member of the Royal Danish Academy of Sciences and Letters
and served on the board of directors of the Carlsberg Foundation
.
He was state geologist 1917-1931. In 1931, he succeeded C.H. Ostenfeld
Carl Hansen Ostenfeld
Carl Emil Hansen Ostenfeld was a Danish systematic botanist. He graduated from the University of Copenhagen under professor Eugenius Warming. He was a keeper at the Botanical Museum 1900-1918, when he became professor of botany at the Royal Veterinary and Agricultural College...
as professor of botany
Botany
Botany, plant science, or plant biology is a branch of biology that involves the scientific study of plant life. Traditionally, botany also included the study of fungi, algae and viruses...
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...
and director of the Copenhagen Botanical Garden, a position he held until his retirement in 1955. His scientific works mainly concern vegetation history during the Eemian interglacial
Eemian interglacial
The Eemian was an interglacial period which began about 130,000 years ago and ended about 114,000 years ago. It was the second-to-latest interglacial period of the current Ice Age, the most recent being the Holocene which extends to the present day. The prevailing Eemian climate is believed to...
, the late glacial period of the Wisconsin glaciation
Wisconsin glaciation
The last glacial period was the most recent glacial period within the current ice age occurring during the last years of the Pleistocene, from approximately 110,000 to 10,000 years ago....
and in the Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
investigated using pollen analysis
Pollen analysis
Analysis of the distribution of pollen grains of various species contained in surface layer deposits, especially peat bogs and lake sediments, from which a record of past climate may be inferred. Because the lake sediments accumulate over time, a core of the mud will show that the mud at the bottom...
.
Jessen had come into contact with the Irish
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
naturalist Robert Lloyd Praeger
Robert Lloyd Praeger
-Life:Of a Unitarian background, he was born in Holywood, County Down, and grew up in that town where he was educated, first in the school of the Rev McAlister and then at nearby Sullivan Upper School. He worked in the National Library of Ireland in Dublin from 1893 to 1923. He co-founded and...
and made field-work on the quaternary geology of Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
during 1934-1935. Together with his assistant, Frank Mitchell, he was able to describe both the post-glacial
Wisconsin glaciation
The last glacial period was the most recent glacial period within the current ice age occurring during the last years of the Pleistocene, from approximately 110,000 to 10,000 years ago....
vegetation development of Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
and that of the Eemian interglacial
Eemian interglacial
The Eemian was an interglacial period which began about 130,000 years ago and ended about 114,000 years ago. It was the second-to-latest interglacial period of the current Ice Age, the most recent being the Holocene which extends to the present day. The prevailing Eemian climate is believed to...
, with the presence in Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
of such plants as Rhododendron ponticum
Rhododendron ponticum
Rhododendron ponticum, called Common Rhododendron or Pontic Rhododendron, is a species of Rhododendron native to southern Europe and southwest Asia.-Description:...
, Abies alba, Erica scoparia and Buxus sempervirens
Buxus sempervirens
Buxus sempervirens is a flowering plant in the genus Buxus, native to western and southern Europe, northwest Africa, and southwest Asia, from southern England south to northern Morocco, and east through the northern Mediterranean region to Turkey. Buxus colchica of western Caucasus and B...
.
Jessen was acknowledged by honorary doctorates at the University of Cambridge
University of Cambridge
The University of Cambridge is a public research university located in Cambridge, United Kingdom. It is the second-oldest university in both the United Kingdom and the English-speaking world , and the seventh-oldest globally...
and University of Dublin
University of Dublin
The University of Dublin , corporately designated the Chancellor, Doctors and Masters of the University of Dublin , located in Dublin, Ireland, was effectively founded when in 1592 Queen Elizabeth I issued a charter for Trinity College, Dublin, as "the mother of a university" – this date making it...
. He was a member of the Royal Danish Academy of Sciences and Letters
Royal Danish Academy of Sciences and Letters
Royal Danish Academy of Sciences and Letters is a Danish non-governmental science Academy, founded 13 November 1742 by permission of the King Christian VI, as a historical Collegium Antiquitatum...
and served on the board of directors of the Carlsberg Foundation
Carlsberg Foundation
Carlsberg Foundation was founded by J. C. Jacobsen in 1876 and owns 30,3% of the shares in Carlsberg Group and has 74,2% of the voting power.The purpose of the foundation is to run and fund Carlsberg Laboratory, the museum at Frederiksborg Palace, to fund scientific research, run the Ny Carlsberg...
.
Selected scientific works
- Jessen, K. (1920) Moseundersøgelser i det nordøstlige Sjælland. Med Bemærkninger om Træers og Buskes Indvandring og Vegetationens Historie (Bog investigations in Northeast Zealand with notes on the immigration of trees and shrubs and the development of the vegetation). Doctoral dissertation. Danmarks Geologiske Undersøgelse, II.række, 34, 1-243.
- Jessen, K. & V. Milthers (1928) Stratigraphical and palaeontological studies of interglacial fresh-water deposits in JutlandJutlandJutland , historically also called Cimbria, is the name of the peninsula that juts out in Northern Europe toward the rest of Scandinavia, forming the mainland part of Denmark. It has the North Sea to its west, Kattegat and Skagerrak to its north, the Baltic Sea to its east, and the Danish–German...
and northwest GermanyGermanyGermany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
. Danmarks Geologiske Undersøgelser II rk. Vol. 48: 1-379.
- Jessen, K. with the assistance of H. JonassenHagbard JonassenHagbard Jonassen was a Danish botanist, quaternary geologist, war resister and nuclear disarmament proponent. He made a lasting impact on the interpretation of pollen diagrams, incl...
(1935) The composition of the forests in northern Europe in EpipalaeolithicMesolithicThe Mesolithic is an archaeological concept used to refer to certain groups of archaeological cultures defined as falling between the Paleolithic and the Neolithic....
time. Biologiske Meddelelser, Kongelige Danske Videnskabernes Selskab 12 (1): 1-64.
- Jessen, K. (1949) Studies in Late QuaternaryQuaternaryThe Quaternary Period is the most recent of the three periods of the Cenozoic Era in the geologic time scale of the ICS. It follows the Neogene Period, spanning 2.588 ± 0.005 million years ago to the present...
deposits and flora-history of IrelandIrelandIreland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
. Proceedings of the Royal Irish AcademyProceedings of the Royal Irish AcademyThe Proceedings of the Royal Irish Academy is the journal of the Royal Irish Academy, founded in 1785 to promote the study of Science, Polite Literature and Antiquities....
52, sect. B, no. 6: 85-290.