Variation in vegetative water use in the savannas of the North Australian Tropical Transect

Authors

  • Garry D. Cook,

    Corresponding author
    1. CSIRO Sustainable Ecosystems and Cooperative Research Centre for Tropical Savannas, Tropical Ecosystems Research Centre, PMB 44 Winnellie, NT 0822, Australia
      *Corresponding author: Fax +61889448444; E-mail garry.cook@csiro.au
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  • Richard J. Williams,

    1. CSIRO Sustainable Ecosystems and Cooperative Research Centre for Tropical Savannas, Tropical Ecosystems Research Centre, PMB 44 Winnellie, NT 0822, Australia
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  • Lindsay B. Hutley,

    1. Cooperative Research Centre for Tropical Savannas, Faculty of Science, Information Technology and Education, Northern Territory University, NT 0909, Australia
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  • Anthony, P. O'Grady,

    1. Cooperative Research Centre for Tropical Savannas, Faculty of Science, Information Technology and Education, Northern Territory University, NT 0909, Australia
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    • Current address: Key Centre for Tropical Wildlife Management Northern Territory University, NT, 0909, Australia

  • Adam C. Liedloff

    1. CSIRO Sustainable Ecosystems and Cooperative Research Centre for Tropical Savannas, Tropical Ecosystems Research Centre, PMB 44 Winnellie, NT 0822, Australia
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*Corresponding author: Fax +61889448444; E-mail garry.cook@csiro.au

Abstract

Abstract. The decline in tree density on sandy soils in savannas is highly correlated with declining mean annual rainfall along the North Australian Tropical Transect (NATT). We reanalyse various data on water use by individual trees and argue that a common relationship can be used to estimate annual water use by tree stands along the NATT from ca. 600 mm mean annual rainfall to at least 1600 mm. Where rainfall is less than 600 mm, trees of a given size use less water than at sites where rainfall is higher. We use these relationships to relate water use at the stand scale with mean annual rainfall along the NATT. From this we show that the empirical data imply that the minimum depth of sandy soil that needs to be exploited by trees declines with increasing aridity along the NATT from more than 5 m to less than 1 m. This finding is consistent with other observations and the pattern that with increasing aridity, an increasing proportion of rainfall coming from isolated storms rather than from periods of extended monsoon activity.

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