Journal Article

Contemporary biogenic formation of clay pavements by eucalypts: further support for the phytotarium concept

John S. Pate and William H. Verboom

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 103, issue 5, pages 673-685
Published in print March 2009 | ISSN: 0305-7364
Published online January 2009 | e-ISSN: 1095-8290 | DOI:
Contemporary biogenic formation of clay pavements by eucalypts: further support for the phytotarium concept

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry


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Background and Aims

Clayey (sodosolic) pavements were studied in lateral root catchments of eucalypts where mixed myrtaceous:proteaceous vegetation was colonizing a dune of quartzitic sand blown out from a playa lake during late Pleistocene times. The site at Chillinup in south-west Western Australia provided an opportunity to examine these signature pavements in an unequivocally recent setting, and to assess their effects on competing non-eucalypt vegetation.


Pavements were located, and their extents and depths assessed by probing with steel rods, followed by corings and pit excavations using an air spade. Listings of plant species, growth forms and root morphologies were assembled for different vegetation zones in a representative transect across the dune. A deep cutting through the dune provided details on pavement morphology and modifications to the sand deposit bioengineered by eucalypt and heath vegetation.

Key Results

Clay pavements comprised closely spaced, round-topped columns whose mean diameters and depths varied between eucalypt species. Incipient pavement formation was characterized by clumps of clay deposited around fine root material. Pavements appeared to have been synthesized in situ from locally accessed and imported constituents. Understoreys on superficial pavements of a tree eucalypt were considerably less dense and biodiverse than on the deeper pavements of two mallee species, whilst most profuse vegetation cover was encountered in heath on unmodified (non-pavemented) sand. Certain species were restricted to superficially located pavements, whilst other ‘generalist’ species occurred widely across the dune. Relict pavements formed by earlier generations of eucalypts were present in certain areas of the transect and in soil profiles of the cutting. Some relict pavements colonized by proteaceous shrubs were overprinted with ferricrete.


Clay pavements formed by eucalypts have pronounced effects on understorey vegetation and may have been instrumental in establishment of the complex mosaics of mallee-woodland and proteaceous heathland observed across semi-arid landscapes of south-west Western Australia. Findings are related to earlier observations on the range of plant-mediated changes in soil profiles discussed in the recently advanced ‘Phytotarium’ concept.

Keywords: Biomineralization; eucalypt roots; niche construction; soil profiles; woody plants; semi-arid ecosystems; vegetation mosaics; competing phytotaria

Journal Article.  8300 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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