Journal Article

Neoformation of clay in lateral root catchments of mallee eucalypts: a chemical perspective

William H. Verboom, John S. Pate and Mehrooz Aspandiar

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 105, issue 1, pages 23-36
Published in print January 2010 | ISSN: 0305-7364
Published online November 2009 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcp261
Neoformation of clay in lateral root catchments of mallee eucalypts: a chemical perspective

More Like This

Show all results sharing these subjects:

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

GO

Show Summary Details

Preview

Background and Aims

A previous paper (Annals of Botany 103: 673–685) described formation of clayey pavements in lateral root catchments of eucalypts colonizing a recently formed sand dune in south-west Western Australia. Here chemical and morphological aspects of their formation at the site are studied.

Methods

Chemical and physical examinations of soil cores through pavements and sand under adjacent heath assessed build-up of salts, clay and pH changes in or below pavements. Relationships of root morphology to clay deposition were examined and deposits subjected to scanning electron microscopy and energy-dispersive X-ray analysis. Xylem transport of mineral elements in eucalypt and non-eucalypt species was studied by analysis of xylem (tracheal) sap from lateral roots.

Key Results

The columns of which pavements are composed develop exclusively on lower-tier lateral roots. Such sites show intimate associations of fine roots, fungal filaments, microbiota and clay deposits rich in Si, Al and Fe. Time scales for construction of pavements by eucalypts were assessed. Cores through columns of pavemented profiles showed gross elevations of bulk density, Al, Fe and Si in columns and related increases in pH, Mg and Ca status in lower profiles. A cutting through the dune exhibited pronounced alkalinity (pH 7–10) under mallee woodland versus acidity (pH 5–6·5) under proteaceous heath. Xylem sap analyses showed unusually high concentrations of Al, Fe, Mg and Si in dry-season samples from column-bearing roots.

Conclusions

Deposition of Al–Fe–Si-rich clay is pivotal to pavement construction by eucalypts and leads to profound chemical and physical changes in relevant soil profiles. Microbial associates of roots are likely to be involved in clay genesis, with parent eucalypts supplying the required key mineral elements and carbon sources. Acquisition of the Al and Fe incorporated into clay derives principally from hydraulic uplift from ground water via deeply penetrating tap roots.

Keywords: Niche construction; eucalypts; root morphology; xylem transport; hydraulic lift; element mining; soil formation; biomineralization; soil pans; duplex soils

Journal Article.  9916 words.  Illustrated.

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

Full text: subscription required

How to subscribe Recommend to my Librarian

Users without a subscription are not able to see the full content. Please, subscribe or login to access all content.