The Raunkiær system is a system for categorizing plants using plant life-form categories, devised by Danes botany Christen C. Raunkiær and later extended by various authors.
History
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 language the following year.
[Raunkiær, C. (1905) Types biologiques pour la géographie botanique. Oversigt over Det Kongelige Danske Videnskabernes Selskabs Forhandlinger, 1905, 347–438.] Raunkiær elaborated further on the system and published this in
Danish language in 1907.
[Raunkiær, C. (1907) Planterigets Livsformer og deres Betydning for Geografien. Gyldendalske Boghandel – Nordisk Forlag, København and Kristiania. 132 pp., (PDF).][Ch. 2 in Raunkiær (1934): The life-forms of plants and their bearings on geography, p. 2-104.]
The original note and the 1907 paper were much later translated to English language and published with Raunkiær's collected works.[Ch. 1 in Raunkiær (1934): Biological types with reference to the adaption of plants to survive the unfavourable season, p. 1.][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". . Note: These are not all of Raunkiær's publications, only those on plant form and geography.]
Modernization
Raunkiær's life-form scheme has subsequently been revised and modified by various authors,
[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, [2] .][Müller-Dombois, D. & Heinz Ellenberg (1974) Aims and methods in vegetation ecology. John Wiley & Sons, New York. Reprint 2003, Blackburn Press, ][Shimwell, D.W. (1971) The Description and Classification of Vegetation. Sidgwick & Jackson, London. ] 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.
Subdivisions
The subdivisions of the Raunkiær system are premised on the location of the
bud of a plant during seasons with adverse conditions, i. e. cold seasons and dry seasons:
Phanerophytes
These plants, normally woody
, grow stems into the air, with their resting buds being more than 50 cm above the soil surface,
e.g.
and
, and also epiphytes, which Raunkiær later separated as a distinct class (see below).
Raunkiær further divided the phanerophytes according to height as
-
Megaphanerophytes,
-
Mesophanerophytes,
-
Microphanerophytes, and
-
Nanophanerophytes.
Further division was premised on the characters of duration of foliage, i. e. evergreen or deciduous, and presence of covering
bracts on buds, for 12 classes. Three further divisions were made to increase the total of classes to 15:
-
Phanerophytic succulent plant,
-
Phanerophytic epiphytes, and
-
Phanerophytic herbs.
Epiphytes
were originally included in the phanerophytes (see above) but then separated because they do not grow in soil, so the soil location is irrelevant in classifying them. They form characteristic communities of moist climatic conditions.
Chamaephytes
These plants have buds on persistent shoots near the soil surface; woody plants with perennating buds borne close to the soil surface, a maximum of 25 cm above the soil surface, e.g.,
bilberry and
Vinca.
Hemicryptophytes
These plants have buds at or near the soil surface, e.g.
common daisy and
dandelion, and are divided into:
-
Protohemicryptophytes: only cauline foliage;
-
Partial rosette plants: both cauline and basal rosette foliage; and
-
Rosette plants: only basal rosette foliage.
Cryptophytes
These plants have subterranean or under water resting buds, and are divided into:
-
Geophytes: rest in dry soil as a rhizome, bulb, corm, et cetera, e.g. crocus and tulip, and are subdivided into:
-
Rhizome geophytes,
-
Stem-tuber geophytes,
-
Root-tuber geophytes,
-
Bulb geophytes, and
-
Root geophytes.
-
Helophytes: rest in marshy or wet soil, e.g. reedmace and marsh-marigold; and
-
Hydrophytes: rest submerged under water, e.g. Nymphaeaceae and frogbit.
Therophytes
These are
that complete their lives rapidly in favorable conditions and survive the unfavorable cold or dry season in the form of seeds. About 6% of plants are therophytes but their proportion is much higher in regions with a hot, dry summer.
Aerophytes
Aerophytes were a later addition to the system.
These are plants that obtain moisture and nutrients from the air and rain.
They usually grow on other plants yet are not
parasitic on them. These are
and are like epiphytes but whose root system have been reduced.
They occur in communities that inhabit exclusively hyper-arid areas with abundant fog.
[ Like epiphytes and hemicryptophytes, their are near the soil surface. Some Tillandsia species are classified as aerophytes.
]
Popular references
Farley Mowat, in his book, Never Cry Wolf, described using a Raunkiær's Circle in making a "cover degree" study to determine the ratios of various plants one to the other. He spoke of it as "a device designed in hell."
