buttress root

{{short description|Large, wide roots on all sides of a shallowly rooted tree}}

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Buttress roots, also known as plank roots or stilt roots, are large, wide roots on all sides of a shallowly rooted tree. Typically, they are found in nutrient-poor tropical forest soils that may not be very deep. They may prevent the tree from falling over (hence the name buttress).

Buttresses are tension elements, being larger on the side away from the stress of asymmetrical canopies.Young, T. P. and V. Perkocha. "Treefalls, crown asymmetry, and buttresses". Journal of Ecology 82:319-324. The roots may intertwine with buttress roots from other trees and create an intricate mesh, which may help support trees surrounding it. They can grow up to {{convert|30|ft|m|0}} tall, spread for {{cvt|100|ft}} above the soil, and then continue another 100 feet below. When the roots spread horizontally, they are able to cover a wider area for collecting nutrients. They stay near the upper soil layer because all the main nutrients are found there.{{cite journal|author1=Crook, M. J. |author2=Ennos, A. R. |author3=Banks, J. R. |year=1997 |title=The function of buttress roots: a comparative study of the anchorage systems of buttressed (Aglaia and Nephelium ramboutan species) and non-buttressed (Mallotus wrayi) tropical trees |journal=Journal of Experimental Botany |volume=48 |issue=9 |pages=1703–1716 |doi=10.1093/jxb/48.9.1703 |doi-access=free}}

Buttress roots vary greatly in size from barely discernable to many square yards (square meters) of surface. The largest for which there is photographic evidence is a Moreton Bay Fig (Ficus macrophylla) at Fig Tree Pocket (an outlying district of Brisbane, Queensland) which was photographed in 1866 with an adult man. The buttresses were {{cvt|40|to|50|ft}} long and {{cvt|35|to|40|ft}} in height.{{cite book| last= Kennedy | first= Edward B. | date= 1902 | title= The Black Police of Queensland | location= London | publisher= John Murray | at=Photo facing p. 200 with human figure}} Halfway out the buttress is twice the height of the man. The tree died in 1893 from flood damage.

The tallest buttresses are those of Huberodendron (Bombacaceae) of the Amazon basin which extend up to {{cvt|70|ft}} up a tree about {{cvt|145|ft}} in height.{{cite book| last= Whitmore | first= Timothy C. | date= 1990 | title= An Introduction to Tropical Rain Forests | location= Oxford | publisher= Clarendon Press | at= p. 51 (photo fig 3.31)}}

The most extensive buttresses are those of the Kapok, or Silk Cotton Tree (Ceiba pentandra), of the Neotropics and tropical Africa. The buttresses can extend outwards as much as {{cvt|65|ft}} from the tree as buttresses, then continue as superficial roots for a total of {{cvt|165|ft}}.{{cite book| last1= Furley | first1= Peter A. D.Phil. | last2= Newey | first2= Walter W. Ph.D. |date= 1983 | title= Geography of the Biosphere | location=London | publisher= Butterworth | at=page 279 (fig. 12.5 with caption)}}