In phytosociology and community ecology an association is a type of ecological community with a predictable species composition, consistent physiognomy (structural appearance) which occurs in a particular habitat type.:181 The term was first coined by Alexander von Humboldt:16 and formalised by the International Botanical Congress in 1910.:182
An association can be viewed as a real, integrated entity shaped either by species interactions or by similar habitat requirements, or it can be viewed as merely a common point along a continuum. The former view was championed by American ecologist Frederic Clements, who viewed the association as a whole that was more than the sum of its parts, and by Josias Braun-Blanquet, a Swiss-born phytosociologist. On the other end of the argument was American ecologist Henry Gleason,:182–183 who saw these groupings of plant species as a coincidence produced by the "fluctuation and fortuitous immigration of plants, and an equally fluctuating and variable environment".
- Barbour, Michael G.; Jack H. Burk; Wanna D. Pitts, Frank S. Gilliam; Mark W. Schwartz (1999). Terrestrial Plant Ecology (Third ed.). Addison Wesley Longman.
- Willner, Wolfgang (2006). "The association concept revisited". Phytocoenologia. 36 (1): 67–76. doi:10.1127/0340-269x/2006/0036-0067.
- Gleason (1935), cited in Barbour et al. 1999, p. 184
- Gleason, H.A. (1926), "The Individualistic Concept of the Plant Association", Bulletin of the Torrey Botanical Club, 53 (1): 7–26, doi:10.2307/2479933, JSTOR 2479933 p.23
- Weber, H.E.; Moravec, J.; Theurillat, J.-P. (2000), "International Code of Phytosociological Nomenclature. 3rd edition" (PDF), Journal of Vegetation Science, 1: 739–768, doi:10.2307/3236580