How does clay constrain woody biomass in drylands?

Roderick J. Fensham*, Don W. Butler, Jenny Foley

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

45 Citations (Scopus)

Abstract

Aim: To investigate the role of clay in limiting the development of woody biomass in drylands. Location: Australia. Methods: Spatial data representing woody biomass, soil clay content and climate for the Australian continent were interpreted to explore the relationship between a moisture index and woody biomass on clay and non-clay substrates. Moisture and soil water potential were investigated through time for clay and sand plains. Sub-soil clay and other soil characteristics were compared between areas with and without high tree mortality after drought. Results: The substantially lower woody biomass on clay soils than non-clay soils in the drylands of the Australian continent verifies the inverse texture effect. A clay floodplain consistently held more water than an adjacent sandplain, but soil moisture in the clay was effectively inaccessible to plants for much longer periods because of more negative values of water potential in the clay soil. Small increases in sub-soil clay were associated with high tree mortality. Main conclusions: Our findings suggest that the 'inverse texture effect', which describes the negative association of woody biomass with soil clay content in drylands, may mostly relate to the moisture-retentive properties of clay rather than being caused by reduced infiltration and enhanced evaporation from clay-rich soils. Our evidence suggests that clay soils constrain woodiness in drylands by exacerbating water stress, and confirm the fundamental role of aridity in determining woody biomass and the global distribution of grassland.

Original languageEnglish
Pages (from-to)950-958
Number of pages9
JournalGlobal Ecology and Biogeography
Volume24
Issue number8
DOIs
Publication statusPublished - 1 Aug 2015
Externally publishedYes

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