Plant life-form
Encyclopedia
Plant life-form schemes constitute a way of classifying plants alternatively to the ordinary species-genus-family scientific classification. In colloquial speech, plants may be classified as tree
s, shrub
s, herb
s (forb
s and graminoids), etc. The scientific use of life-form schemes emphasizes plant function in the ecosystem
and that the same function or "adaptedness" to the environment may be achieved in a number of ways, i.e. plant species that are closely related phylogenetically may have widely different life-form, for example Adoxa and Sambucus are from the same family, but the former is a small herbaceous plant
and the latter is a shrub
or tree
. Conversely, unrelated species may share a life-form through convergent evolution
. The most widely applied life-form scheme is the Raunkiær system.
Life-form and growth-form are essentially synonymous concepts, despite attempts to restrict the meaning of growth-form to types differing in shoot architecture. Most life form schemes are concerned with vascular plant
s only. Plant construction types may be used in a broader sense to emcompass planktophytes, benthophytes (mainly algae) and terrestrial plant
s.
("livsform") in his 1895 book Plantesamfund
, but was translated to "growthform" in the 1909 English version Oecology of Plants
. Nevertheless, earlier authors did classify species according to physiognomy , but were explicit about the entities being merely plactical classes without any relation to plant function. A marked exception was A. P. de Candolle
attempt to construct a natural system of botanical classification. His system was based on the height of the lignified stem and on plant longevity. Warming, in his account, is explicit about his Candollean legacy. Warming's first attempt in life-form classification was his work Om Skudbygning, Overvintring og Foryngelse (translated title "On shoot architecture, perennation and rejuvenation" - See line drawings) (1884). The classification was based on his meticulous observations while raising wild plants from seed in the Copenhagen Botanical Garden. Fourteen informal groups were recognized, based on longevity of the plant, power of vegetative propagation, duration of tillers, hypogeous or epigeous type of shoots, mode of wintering, and degree and mode of branching of rhizome
s.
Warming developed his life-form scheme further in his "On the life forms in the vegetable kingdom". He presented a hierarchic scheme, first dividing plants into heterotrophic and autotrophic, the latter group then into aquatic
and terrestrial
, the land plants into muscoid, lichenoid, lianoid and all other autonomous land plants, which again were divided into monocarpic
and polycarpic
. This system was incorporated into the English version of his 1895 book Oecology of Plants. Warming continued
working on plant life-forms and intended to develop his system further. However, due to high age and illness, he was able to publish a draft of his last system only
Following Warming's line of emphasizing functional characters, Oscar Drude
devised a life-form scheme in his Die Systematische und Geographische Anordnung der Phanerogamen (1887). This was, however, a hybrid between physiognomic and functional classification schemes as it recognized monocots and dicots as groups. Drude
later modified his scheme in Deutschlands Pflanzengeographie (1896), and this scheme was adopted by the influential American plant ecologists Frederic Clements
and Roscoe Pound
Christen C. Raunkiær
's classification (1904) recognized life-forms (first called "biological types") on the basis of plant adaptation to survive the unfavorable season, be it cold or dry, that is the position of buds with respect to the soil surface. In subsequent works, he showed the correspondence between gross climate and the relative abundance of his life-forms..
G.E. Du Rietz reviewed the previous life-form schemes in 1931 and strongly criticized the attempt to include functional characters. He tabulated six parallel ways of life-form classification:
General plant physiognomy
Growth-forms / shoot architecture
Periodicity life-form - seasonal physiognomic variation
Bud height life-form (Raunkiær's scheme),
Bud structure life-form
Leaf life-form - form, size, duration, texture of leaves.
Later authors have combined these or other types of unidimensional life-form schemes into more complex schemes, in which life-forms are defined as combinations of states of several characters. Examples are the schemes proposed by Pierre Dansereau
and Stephan Halloy. These schemes approach the concept of plant functional type, which has recently replaced life-form in a narrow sense.
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
s, shrub
Shrub
A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...
s, herb
Herb
Except in botanical usage, an herb is "any plant with leaves, seeds, or flowers used for flavoring, food, medicine, or perfume" or "a part of such a plant as used in cooking"...
s (forb
Forb
A forb is a herbaceous flowering plant that is not a graminoid . The term is used in biology and in vegetation ecology, especially in relation to grasslands and understory.-Etymology:...
s and graminoids), etc. The scientific use of life-form schemes emphasizes plant function in the 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....
and that the same function or "adaptedness" to the environment may be achieved in a number of ways, i.e. plant species that are closely related phylogenetically may have widely different life-form, for example Adoxa and Sambucus are from the same family, but the former is a small herbaceous plant
Herbaceous plant
A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...
and the latter is a shrub
Shrub
A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...
or tree
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
. Conversely, unrelated species may share a life-form through convergent evolution
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...
. The most widely applied life-form scheme is the Raunkiær system.
Life-form and growth-form are essentially synonymous concepts, despite attempts to restrict the meaning of growth-form to types differing in shoot architecture. Most life form schemes are concerned with vascular plant
Vascular plant
Vascular plants are those plants that have lignified tissues for conducting water, minerals, and photosynthetic products through the plant. Vascular plants include the clubmosses, Equisetum, ferns, gymnosperms and angiosperms...
s only. Plant construction types may be used in a broader sense to emcompass planktophytes, benthophytes (mainly algae) and terrestrial plant
Terrestrial plant
A terrestrial plant is one that grows on land. Other types of plants are aquatic , epiphytic , lithophytes and aerial ....
s.
History
The term life-form was first coined by Eugenius WarmingEugenius Warming
Johannes Eugenius Bülow Warming , known as Eugen Warming, was a Danish botanist and a main founding figure of the scientific discipline of ecology...
("livsform") in his 1895 book Plantesamfund
Plantesamfund
Plantesamfund - Grundtræk af den økologiske Plantegeografi, published in Danish in 1895 by Eugen Warming, and in English in 1909 as Oecology of Plants: An Introduction to the Study of Plant Communities, by Warming and Martin Vahl, was the first book to be published having the word ecology in its...
, but was translated to "growthform" in the 1909 English version Oecology of Plants
Plantesamfund
Plantesamfund - Grundtræk af den økologiske Plantegeografi, published in Danish in 1895 by Eugen Warming, and in English in 1909 as Oecology of Plants: An Introduction to the Study of Plant Communities, by Warming and Martin Vahl, was the first book to be published having the word ecology in its...
. Nevertheless, earlier authors did classify species according to physiognomy , but were explicit about the entities being merely plactical classes without any relation to plant function. A marked exception was A. P. de Candolle
A. P. de Candolle
Augustin Pyramus de Candolle also spelled Augustin Pyrame de Candolle was a Swiss botanist. René Louiche Desfontaines launched Candolle's botanical career by recommending him at an herbarium...
attempt to construct a natural system of botanical classification. His system was based on the height of the lignified stem and on plant longevity. Warming, in his account, is explicit about his Candollean legacy. Warming's first attempt in life-form classification was his work Om Skudbygning, Overvintring og Foryngelse (translated title "On shoot architecture, perennation and rejuvenation" - See line drawings) (1884). The classification was based on his meticulous observations while raising wild plants from seed in the Copenhagen Botanical Garden. Fourteen informal groups were recognized, based on longevity of the plant, power of vegetative propagation, duration of tillers, hypogeous or epigeous type of shoots, mode of wintering, and degree and mode of branching of rhizome
Rhizome
In botany and dendrology, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...
s.
Warming developed his life-form scheme further in his "On the life forms in the vegetable kingdom". He presented a hierarchic scheme, first dividing plants into heterotrophic and autotrophic, the latter group then into aquatic
Aquatic plant
Aquatic plants are plants that have adapted to living in aquatic environments. They are also referred to as hydrophytes or aquatic macrophytes. These plants require special adaptations for living submerged in water, or at the water's surface. Aquatic plants can only grow in water or in soil that is...
and terrestrial
Terrestrial plant
A terrestrial plant is one that grows on land. Other types of plants are aquatic , epiphytic , lithophytes and aerial ....
, the land plants into muscoid, lichenoid, lianoid and all other autonomous land plants, which again were divided into monocarpic
Monocarpic
Monocarpic plants are those that flower, set seeds and then die. Other terms with the same meaning are hapaxanth and semelparous. The term was first used by Alphonse de Candolle....
and polycarpic
Polycarpic
Polycarpic plants are those that flower and set seeds many times before dying....
. This system was incorporated into the English version of his 1895 book Oecology of Plants. Warming continued
working on plant life-forms and intended to develop his system further. However, due to high age and illness, he was able to publish a draft of his last system only
Following Warming's line of emphasizing functional characters, Oscar Drude
Carl Georg Oscar Drude
Carl Georg Oscar Drude was a German botanist.- References :...
devised a life-form scheme in his Die Systematische und Geographische Anordnung der Phanerogamen (1887). This was, however, a hybrid between physiognomic and functional classification schemes as it recognized monocots and dicots as groups. Drude
Carl Georg Oscar Drude
Carl Georg Oscar Drude was a German botanist.- References :...
later modified his scheme in Deutschlands Pflanzengeographie (1896), and this scheme was adopted by the influential American plant ecologists Frederic Clements
Frederic Clements
Frederic Edward Clements was an American plant ecologist and pioneer in the study of vegetation succession.-Biography:...
and Roscoe Pound
Roscoe Pound
Nathan Roscoe Pound was a distinguished American legal scholar and educator. He was Dean of Harvard Law School from 1916 to 1936...
Christen C. Raunkiær
Christen C. Raunkiær
Christen Christensen Raunkiær was a Danish botanist, who was a pioneer of plant ecology. He is mainly remembered for his scheme of plant strategies to survive an unfavourable season and his demonstration that the relative abundance of strategies in floras largely corresponded to the Earth's...
's classification (1904) recognized life-forms (first called "biological types") on the basis of plant adaptation to survive the unfavorable season, be it cold or dry, that is the position of buds with respect to the soil surface. In subsequent works, he showed the correspondence between gross climate and the relative abundance of his life-forms..
G.E. Du Rietz reviewed the previous life-form schemes in 1931 and strongly criticized the attempt to include functional characters. He tabulated six parallel ways of life-form classification:
General plant physiognomy
Growth-forms / shoot architecture
Periodicity life-form - seasonal physiognomic variation
Bud height life-form (Raunkiær's scheme),
Bud structure life-form
Leaf life-form - form, size, duration, texture of leaves.
Later authors have combined these or other types of unidimensional life-form schemes into more complex schemes, in which life-forms are defined as combinations of states of several characters. Examples are the schemes proposed by Pierre Dansereau
Pierre Dansereau
Pierre Dansereau, was a Canadian ecologist known as one of the "fathers of ecology".-Biography:...
and Stephan Halloy. These schemes approach the concept of plant functional type, which has recently replaced life-form in a narrow sense.