Henry Allen Gleason--Chronology

1882 Henry Allen Gleason born near Dalton City, Illinois
1892 moved into town of Decatur, Illinois

Living at the edge of the city, with woods and a river just a short distance away, I turned to the woods for recreation

1897 at the age of 15, Gleason entered the University of Illinois

I was now fully decided to be a botanist......simply because I loved plants

* Gleason had entered one of the few institutions in the United States in which, prior to the end of the 19th century, ecological ideas were being taken seriously and ecological practice going on (Charles C. Adams and Stephen A. Forbes taught here).

* Influenced by Charles A. Hart, an entomologist who took Gleason on his first real botanical trip (a collecting trip) in 1900 to Grand Tower, Illinois

* Majored in botany and studied plant communities;

For my B.S. thesis I took as a subject the flora of the prairies...tried to compile a list of all the prairie plants of Illinois and discuss their distributions and associations as best I could.

* Influenced early on by Cowles (distribution of vegetation lay within an understanding of erosion cycles and the process of topographical change which would enable the ecologist to interpret and classify vegetation upon a developmental basis)

* worked in the Herbarium in his sophomore year under direction of George P. Clinton Clinton had more influence on me botanically than any other man 1901 B.S. Thesis The flora of the Prairie -received degree from Illinois under direction of Thomas Burrill (head of botany dept.)

-Gleason studied the vegetation of the Ozark Hills in southern Illinois

1904 Masters thesis entitled, The vegetation of the Ozark region in southern Illinois

1905 went on expedition to Isle Royale in Lake Superior under direction of Charles Adams

I had gained experience with a new flora and with new types of vegetation. I had added to my knowledge of ecology (Gleason)

* Clements book, Research Methods in Ecology published

* Gleason no longer in complete agreement with Cowles

1907 Ph.D. from Columbia University. Doctoral research done primarily at New York Botanical Gardens and entirely taxonomic

* became instructor at University of Illinois

* published The botanical survey of the Illinois River Valley sand Region area of interaction between prairie and forest vegetation

1907-1918 * published 14 papers belonging to ecology and plant ecology

1910 published The vegetation of the inland sand deposits of Illinois. this paper expressed disagreement with Clements on two points;

1) Gleasons distinctive floristic perspective on vegetation the most important feature of the association is not the habitat but the plant(Gleason)

the plant itself is in many cases the controlling agent in the environment: the differentiation of definite associations is mainly due to the interrelation of the component plants: and the physical environment is as often the result as the cause of vegetation ....the establishment of a plant in the place which it occupies is conditioned quite as much by the influence of other plants as by that of the physical environment (Gleason)

2)Gleason described the first example of a reversed succession -Clements thought succession had to be developmental and progressive

1912 published An isolated prairie grove and its phytogeographical significance

1913 Gleason made director of Biological Station on Douglas Lake in Northern Michigan * field work done here

* went on year-long voyage around the world -tropical vegetation influenced him in later years when considering his perception of the plant community

* published Some interesting plants from the vicinity of Douglas Lake

* published The relation of forest distribution and prairie fires in the Middle West

1916 published Botanical sketches from the Asiatic tropics

1917-1918 Back in Michigan, continued research on;

1)role of fire in the maintenance of the prairie 2)interactions between coniferous and deciduous woodland
3)vegetational history of the Middle West -argued from these studies that, no two species have identical environmental demands(Gleason).
Therefore plants did not occur in precisely repeating groups. Individuals of the same species were capable of growing in different habitats and with different associated species.

*from studies of the beech-maple forest around Douglas Island, Gleason argued that no two areas were identical in terms of species composition or the relative numbers of each species

=Individualistic concept of the plant community.....a floristic approach entailed giving primacy to the study of the individual plants and their species

1917 published The structure and development of the plant association which identified Gleasons individualistic concept. The three major theories of the time according to Gleason were;

1)the association is an organism, or quasi organism...held together by a close bond of interdependence...with properties different from but analogous to, the vital principles of an individual, including phenomena similar to birth, life, and death, as well as constant structural features comparable to the structures of the individual(Clements)

2) the association is not an organism, but a series of separate similar units, variable in size but repeated in numerous examples. As such it is comparable to a species (Cooper and Nichols)

3)the vegetation unit is a temporary and fluctuating phenomena, dependent. in its origin, its structure, and its disappearance, on the selective action of the environment and on the nature of the surrounding vegetation (Gleason)

1918 published "The local distribution of introduced species near Douglas Lake, Michigan"
* published "Notes on the introduced flora of the Douglas region"

1919 Assistant Director at the New York Botanical Garden

1920 * published "Some applications of the quadrat method, based on research done at Douglas Lake"

1922 published The vegetational history of the Middle West (paper on plant geography)
-ecology and floristics combined
-tried to indicate that the ecologists understanding of vegetation could be enhanced by a consideration of floristics and floristic history
1923 * published Evolution and geographical distribution of the genus Vernonia in North America

1925 * published Species and area

1926 spent time in Puerto Rico doing an ecological survey of the island two sample quadrats with precisely the same structure can scarcely be discovered(Gleason)

*suggested that vegetation consisted of a continuum of variation and argued that it was a universal feature of vegetation that vegetation-types graded into one another over long distances

* published The individual concept of the plant association
* published Plant associations and their classification

* Ithaca Conference
-entire half day of this conference devoted to recently published Gleason paper on individualistic concept (1926)
-concept favored by taxonomists and rejected by ecologists

1927 continued work at the Botanical Garden
*did mostly taxonomic work
* published Further views on the succession concept

1931 * published The fundamental principles in the classification of
vegetation

1933 * published On concepts in

1936-1951 Acting Director of Botanical garden

1938 Conference at Cold Spring Harbor

* presented (1926) paper on individualistic concept and1927 paper on the theory of plant succession
* was gaining more acceptance among ecologists

1939 * published The individualistic concept of the plant association

1940-1947 member of the Nomenclature Committee of the ecological society

1944 wrote autobiography (unpublished)

1951 retired from Botanical Gardens

1956 Gleason presented with Certificate of Merit of the Botanical Society of America

1959 Gleason honored by the Eminent Ecologist Award of the Ecological
Society of America

1964 co-author (with Arthur Cronquist) of book, "The National Geography of Plants"

References for this outline came from:

Nicolson, Malcolm. 1990. Henry Allan Gleason and the individualistic hypothesis: The structure of a botanists career. Botanical Review 56: 91-161.