Plant life-form

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 trees, shrubs, herbs (forbs 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 architectureDu Rietz, G. E. (1931) Life-forms of terrestrial flowering plants. I. Acta Phytogeographica Suecica 3 (1): 95 pp.] . Most life form schemes are concerned with vascular plants only. "Plant construction types" may be used in a broader sense to emcompass "planktophytes", "benthophytes" (mainly algae) and terrestrial plants [Raven, J.A. (1986) Evolution of plant life forms. Pages 421-492 in T.J. Givnish (ed.) On the economy of plant form and function. Cambridge University Press, Cambridge. [http://books.google.com/books?id=0YZAlb9ITcAC&hl=sv] ] .

History

The term life-form was first coined by Eugen Warming ("livsform") in his 1895 book PlantesamfundWarming, E. (1895) Plantesamfund - Grundtræk af den økologiske Plantegeografi. P.G. Philipsens Forlag, Kjøbenhavn; Chapter 2 "Livsform (Vegetationsform)" p. 3-6.] , but was translated to "growthform" in the 1909 English version "Oecology of Plants". Nevertheless, earlier authors did classify species according to physiognomy [Humboldt, A. von (1806) Ideen zu einer Physiognomik der Gewächse. Stuttgart. English translation as "Ideas for a physiognomy of plants", pp. 210-352 in "Views of nature: or Contemplations on the sublime phenomena of creation" by E.C. Otté and Henry G. Bohn. London, H.G. Bohn, 1850.] [Kerner von Marilaun, A. (1863) Das Pflanzenleben der Donauländer. Innsbruck. English translation by H.S. Connard, The Background of Plant Ecology. Iowa State College, Ames, 1950. Reprinted 1977, Arno Press, in the "History of Ecology Series". ISBN 0405104030] [Grisebach, A. (1872) Die Vegetation der Erde nach ihrer klimatischen Anordnung. Engelmann, Leipzig.] , 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 [De Candolle, A.P. (1818) Regni vegetabilis systema naturale, Vol. 1. Paris.] . His system was based on the height of the lignified stem and on plant longevity. Warming, in his account, is explicit about his Candollean legacyWarming, E. (1909) Oecology of Plants - an introduction to the study of plant-communities, translated by P. Groom and I. B. Balfour. Clarendon Press, Oxford. 422 pp.] . Warming's first attempt in life-form classification was his work "Om Skudbygning, Overvintring og Foryngelse" (translated title "On shoot architecture, perennation and rejuvenation" - ) (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 rhizomes.

Warming developed his life-form scheme further in his "On the life forms in the vegetable kingdom" [Warming, E. (1908) Om planterigets livsformer [translated title: On the life forms in the vegetable kingdom] . G.E.C. Gad, København.] . 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 [Warming, E. (1923) Økologiens Grundformer – Udkast til en systematisk Ordning [translated title: Fundamental ecological forms - draft for a system] . Kongelige Danske Videnskabernes Selskabs Skrifter - Naturvidenskabelig og Mathematisk Afdeling, 8. Rk., vol. 4: 120-187.]

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 [Pound, R. and Clements, F.E. (1898) Phytogeography of Nebraska. Lincoln, Nebraska. Reprinted in the "History of Ecology Series" by Arno Press, New York, 1977. ISBN 0405104170]

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 [Raunkiær, C. (1904) Om biologiske Typer, med Hensyn til Planternes Tilpasninger til at overleve ugunstige Aarstider. Botanisk Tidsskrift 26, p. XIV. Also as Ch. 1: Biological types with reference to the adaption of plants to survive the unfavourable season, in: The Life Forms of Plants and Statistical Plant Geography. Oxford University Press, Oxford; p. 1.] . In subsequent works, he showed the correspondence between gross climate and the relative abundance of his life-forms. [Raunkiær, C. (1911) Det arktiske og antarktiske Chamæfyteklima. In: Biologiske Arbejder tilegnede Eug. Warming paa hans 70 Aars Fødselsdag den 3. Nov. 1911. Kjøbenhavn.Also as Ch. 7 in Raunkiær (1934): The Arctic and Antarctic chamaephyte climate, p. 283-302.] [Raunkiær, C. (1914) Sur la végétation des alluvions méditerranéennes françaises. Mindeskrift i Anledning af Hundredeaaret for Japetus Steenstrups Fødsel (eds H.F. E. Jungersen & E. Warming), pp. 1-33. København. Also as Ch. 9 in Raunkiær (1934): On the vegetation of the French mediterranean alluvia, p. 343-367.] [Raunkiær, C. (1918) Über das biologische Normalspektrum. Biologiske Meddelelser / Kongelige Danske Videnskabernes Selskab, 1 (4), 1-17.Also as Ch. 12 in Raunkiær (1934): On the biological normal spectrum, p. 425-434] .

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 [ [http://dx.doi.org/10.2307/1930415 Dansereau, P. (1951) Description and recording of vegetation upon a structural basis. Ecology 32 (2): 172-229] .] and Stephan Halloy [ [http://dx.doi.org/10.2307/3235704 Halloy, S. 1990. A morphological classification of plants, with special reference to the New Zealand alpine flora. Journal of Vegetation Science 1 (3): 291-304.] ] . These schemes approach the concept of plant functional type, which has recently replaced "life-form" in a narrow sense.

ee also

Raunkiær plant life-form

References

External links

[http://ecoqua.ecologia.ufrgs.br/arquivos/Reprints&Manuscripts/Pillar_Orloci_1993-2004_EBook.pdf Pillar, V.D. & L. Orlóci. 2004. Character-Based Community Analysis: The Theory and an Application Program. Electronic Edition available at http://ecoqua.ecologia.ufrgs.br. 213 p.]