Carbon isotope discrimination by a sequence of Eucalyptus species along a subcontinental rainfall gradient in Australia


  • J. M. MIller,

    1. Environmental Biology Group,
    Search for more papers by this author
  • R. J. Williams,

    1. CSIRO Division of Wildlife and Ecology, and Co-operative Research Centre for Tropical Savannas, PMB Box 44, Winnellie, NT 0822, Australia
    Search for more papers by this author
  • G. D. Farquhar

    1. Environmental Biology Group,
    2. Co-operative Research Centre for Greenhouse Accounting, Research School of Biological Sciences, Institute of Advanced Studies, Australian National University, GPO Box 475, Canberra, ACT 2601, Australia, and
    Search for more papers by this author
    • Author to whom correspondence should be addressed.


1. The 13C/12C discrimination (Δ) by a series of co-occurring and replacement Eucalyptus species was measured across an eightfold decrease in rainfall. As Δ is a measure of the stomatal limitation on photosynthesis, it should provide a subcontinental scale measure of water-limited plant physiological performance.

2. Leaf Δ of five of 13 species decreased with decreasing rainfall, seven exhibited no trend, and one increased. Wood Δ decreased in eight species, showed no trend in four, and increased in one species.

3. Species replacements were marked by a shift in Δ reflecting greater stomatal limitation on carbon assimilation.

4. Wood Δ was less variable than leaf Δ.

5. There was a non-linear response of the multispecies average leaf and wood Δ to decreasing total annual rainfall. This response reflected the spatial pattern of the sensitivities of Δ to decreasing rainfall of the individual species. It was not the result of a proposed emergent behaviour where the trend in the multispecies average differed from that of the individual species.

6. Patterns of Δ across the distributions of species (reflecting increasing stomatal limitation on assimilation) did not provide a simple measure of the physiological limits of the distribution of eucalypts in north-western Australia.