Raunkiaer Life Forms Classification Essay

The Raunkiær system is a system for categorizing plants using life-form categories, devised by DanishbotanistChristen C. Raunkiær and later extended by various authors.

History[edit]

It was first proposed in a talk to the Danish Botanical Society in 1904 as can be inferred from the printed discussion of that talk, but not the talk itself, nor its title. The journal, Botanisk Tidsskrift, published brief comments on the talk by M.P. Porsild, with replies by Raunkiær. A fuller account appeared in French the following year.[1] Raunkiær elaborated further on the system and published this in Danish in 1907.[2][3]

The original note and the 1907 paper were much later translated to English and published with Raunkiær's collected works.[4][3][5]

Modernization[edit]

Raunkiær's life-form scheme has subsequently been revised and modified by various authors,[6][7][8] but the main structure has survived. Raunkiær's life-form system may be useful in researching the transformations of biotas and the genesis of some groups of phytophagous animals.[9]

Subdivisions[edit]

The subdivisions of the Raunkiær system are based on the place of the plant's growth-point (bud) during seasons with adverse conditions (cold seasons and dry seasons):

Phanerophytes[edit]

Projecting stems into the air – normally woody perennials - with resting buds more than 25 cm above soil level,[citation needed] e.g. trees and shrubs, but also epiphytes, which Raunkiær separated out as a special group in later versions of the system.

Further subgrouping[edit]

Raunkiær further subdivided the phanerophytes according to height as megaphanerophytes, mesophanerophytes, microphanerophytes, and nanophanerophytes. Other characters used to further subdivide were duration of leaves (evergreen or deciduous) and presence of covering bracts on buds (eight classes in all). Three further classes, phanerophytic stem succulents, phanerophytic epiphytes, and phanerophytic herbs brought the number of subclasses to 12.

Chamaephytes[edit]

Buds on persistent shoots near the ground – woody plants with perennating buds borne close to the ground, no more than 25 cm above the soil surface, (e.g., bilberry and periwinkle).

Hemicryptophytes[edit]

Buds at or near the soil surface, e.g. daisy, dandelion.

Protohemicryptophytes 
only stem leaves
Partial rosette plants 
both stem and basal rosette leaves
Rosette plants 
only basal rosette leaves

Cryptophytes[edit]

Below ground or under water - with resting buds lying either beneath the surface of the ground as a rhizome, bulb, corm, etc., or a resting bud submerged under water. Cryptophytes are divided into 3 groups:

Geophytes 
Resting in dry ground, e.g. crocus, tulip. May be further subdivided into rhizome, stem-tuber, root-tuber, bulb and root geophytes.
Helophytes 
Resting in marshy ground, e.g. reedmace, marsh-marigold.
Hydrophytes 
Resting by being submerged under water, e.g. water-lily, frogbit.

Therophytes[edit]

Annual plants which complete their life-cycle rapidly under favorable conditions and survive the unfavorable cold or dry season in the form of seed. Many desert plants are by necessity therophytes.

Epiphytes[edit]

Epiphytes were originally placed in Phanerophytes (above) but then separated because of irrelevance of soil position.

Aerophytes[edit]

A later addition to the Raunkiær lifeform classification.[10] Plant that obtains moisture and nutrients from the air and rain; usually grows on other plants but not parasitic on them. These are perennial plants whose roots atrophy; some can live on mobile sand dunes; like epiphytes and hemicryptophytes, their buds are near the surface. This group includes some but not all Tillandsia species.

References[edit]

  1. ^Raunkiær, C. (1905) Types biologiques pour la géographie botanique. Oversigt over Det Kongelige Danske Videnskabernes Selskabs Forhandlinger, 1905, 347-438.
  2. ^Raunkiær, C. (1907) Planterigets Livsformer og deres Betydning for Geografien. Gyldendalske Boghandel - Nordisk Forlag, København and Kristiania. 132 pp., (PDF).
  3. ^ abCh. 2 in Raunkiær (1934): The life-forms of plants and their bearings on geography, p. 2-104.
  4. ^Ch. 1 in Raunkiær (1934): Biological types with reference to the adaption of plants to survive the unfavourable season, p. 1.
  5. ^Raunkiær, C. (1934) The Life Forms of Plants and Statistical Plant Geography, being the collected papers of C. Raunkiær. Translated by H. Gilbert-Carter, A. Fausbøll, and A. G. Tansley. Oxford University Press, Oxford. Reprinted 1978 (ed. by Frank N. Egerton), Ayer Co Pub., in the "History of Ecology Series". ISBN 0-405-10418-9. Note: These are not all of Raunkiær's publications, only those on plant form and geography.
  6. ^Ellenberg. H. & D. Mueller-Dombois (1967). A key to Raunkiær plant life-forms with revised subdivisions. Ber. Goebot. Inst. ETH. Stiftg Rubel. Zurich. 37:56-73, [1].
  7. ^Müller-Dombois, D. & H. Ellenberg (1974) Aims and methods in vegetation ecology. John Wiley & Sons, New York. Reprint 2003, Blackburn Press, ISBN 1-930665-73-3
  8. ^Shimwell, D.W. (1971) The Description and Classification of Vegetation. Sidgwick & Jackson, London. ISBN 9780283980633
  9. ^Volovnik, S.V. (2013). "On phylogenetic inertia: a case of Lixinae weevils". Annales de la Société entomologique de France (N.S.):International Journal of Entomology. 49 (3): 240–241. 
  10. ^Galán de Mera, A., M. A. Hagen & J. A. Vicente Orellana (1999) Aerophyte, a New Life Form in Raunkiær's Classification? Journal of Vegetation Science 10 (1): 65-68

Here is your Essay on Major Classification of Community !

The current well-accepted view considers a community as a continuum, however, the plant and animal life of any large area is so complex that it must be separated into subdivisions. In fact the aggregation of organisms in any given locality or habitat must regarded as a unit if the community is to be studied, described, or compared with similar community stands in other habitats.

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To give order to the study of communities, some system of classification is needed, even though the communities of a region often cannot be placed in discrete units. The most widely used classification systems are based on physiognomy, habitat, floristic characteristics like species composition and dominance and com­munity dynamics.

1. Physiognomic Classifications:

Physiognomy, or general appearance, is a highly useful method of naming and delineating communities, particularly in surveying large areas, and as basis for further subdivision of major types into their component communities. Because animal distribution is mainly depended on the structure of vegetation and not on the species composition, therefore, classification by physiognomy willrelate both the animals and the vegetation of an area.

Communi­ties so classified are usually named after the dominant form of life, usually plant, such as the coniferous or deciduous forest, sage­brush, short-grass prairie, and tundra. A few arc named after animals, such as the barnacle—blue mussel (Balanvs—Mytilus) community of the tidal zone. One may grade into the other; so even here the classification may be based on arbitrary, although specific, criteria. Some of the earlier attempts of physiognomic classification by different plant ecologists can be summarized as follows:

Warming (1909) recognised autotrophs and heterotrophs. The aquatic autotrophs, called hydatophytes, were grouped into seven classes, while, the aerial autotrophs were divided into atmophytes, ombrophytes, (plants growing in areas of abundant rainfall), psyebrophytes (plants of cold soils), halophytes (plants of soils having high salt contents), psammophytes (plants of sandy soils), agrophytcs (plants having natural habitat in crop-fields), oxy- lophytes (plants of acidic soils), chasmophytes (plants growing in rock crevices), etc. Raunkiaer (1934) classified plants on the basis of adaptations of life forms to their climates.

He selected about 1000 plant species from all over the world and assigned them to their life forms. Certain plant ecologists have applied Raunkiaer’s classification method to classify Indian communities Iversen (1936) based his classification on the water requirements of plants.

He recognised the following class’s terriphytes (land plants); telmatophytes (aerial plants with aerenchyma), amphiphytes (marsh plants) and limnophytcs (water plants). The physiognomic classification also includes symbolic classification in which different characteristics of a species, such as life form, plant size, leaf shape and size, function, leaf texture, etc., are represented by symbols. Dansereau (1957) has used graphic symbols, while Kuchler (1967) has used several alphabets.

2. Habitat Classification:

In areas where the habitat is well defined, physiographic is used to classify and name communities. Examples of such are sand dunes, cliffs, tidal mud flats, lakes, ponds, and streams.

3. Floristic Classification:

The floristic classification requires detailed study of the indivi­dual community and also involves many concepts like frequency, dominance, constancy, presence and fidelity. The Scandinavian ecologist Du Rietz (l921) classified communities into called sociation, which was defined as a recurring plant community of essentially homogeneous species composition with at least certain dominant species in each layer.

Another floristic unit consociation was proposed for the community if only the upper stratum of a multi-layered community is dominated by one species. Thus, the consociation can be defined as a class composed of individual con­crete associations whose upper strata are dominated by the same species.

European ecologists group communities into classes, orders, alliances, and associations. Association is defined as a community of definite floristic composition, uniform physiognomy and occurring in uniform habitat conditions. The associations are recognized on the basis of common dominant species in several stands and they are used in naming the association, for example, Anogeissus- Boswellia association, Shorea-Terminalia association, or Balanus- Mytilus association. The floristic system of community classification Works much better with plants alone than with animals or with both.

The floristic classification system is modified when the stands are treated as a continuum. The community complex of a major physiognomy is subdivided by species composition and correlated with an environmental gradient arbitrarily divided into five segme­nts: wet, wet mesic, mesic, dry mesic, and dry (Curtis, 1959). For example, the deciduous forest in Wisconsin (USA) has been divided into southern and northern hardwoods and northern forest. These are further divided in a moisture gradient.

The southern hardwoods include the dry southern hardwoods with bur or black or white oak as the dominants; the dry mesic with red oak or basswood; the mesic with sugar maple and beech; the wet mesic with silver maple, elm, and ash; and the wet woods with willow or cottonwood. Such a system recognises the influences of habitat on community composi­tion. Detailed studies on animal distribution also reveal similar influences of animal composition.

4. Dynamic System:

Clements (1928) modified the floristic system by laying great emphasis on the community dynamics. He called the climax vege­tation in a macroclimatic region as “formation” (whenever the vegetation reaches highest development becoming more or less stable for more-or less definite period, under the existing climate, it is called a plant formation).

Each formation was divided into a few associations which were considered units of climax communi­ties in which a few species were dominant. An association was named after the two or three dominant species. The association was further subdivided in a hierarchical series as follows:

i. Consociation:

Unit with a single dominant species. The developmental or communities of a climax consociation are known as conscious.

ii. Faciation:

An association developed under different micro­climatic conditions within the same general climate. It contains two or more dominant species and is characterized by specific precipi­tation, evaporation and temperature. The seral communities are accordingly known as facies.

iii. Location:

This is a localised variant of an association, differing from it in the composition of some main subdominant and chief secondary sepcies. Seral communities are accordingly called locies.

iv. Society:

A community with one or more sub-dominants. The seral communities are called Society.

5. Biome System:

Usually animal and plant communities are studied separately, which unfortunately obscures the wholeness of the community and limits our understanding of its function. To escape this dilemma in part, the distribution of animals can be related to the life form of plants and types of vegetation.

These results in a more inclusive classification, which embraces several plant communities but inclu­des all animal life associated with them; this classification is called a biome. The biome is a broad ecological unit characterized by uniformity and distinctive life forms of the climax species, plant or animal.

It is subdivided into smaller units distinguished by uni­formity and distinctness in the species composition of the climax and its successor stages. Thus the life forms of plants are empha­sized, rather than the taxonomic composition.

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