Leaf water 18O enrichment in different Eucalyptus species - effects of leaf physiology and morphology.
Kahmen, Ansgar*,1, Merchant, Andrew2, Callister, Andrew3, Arndt, Stefan 3, 1 University of California, Berkeley, Berkeley, CA, USA2 University of New South Wales, Sydney, NSW, Australia3 University of Melbourne, Melbourne, VIC, Australia
ABSTRACT- Stable isotopes have been a valuable tool to study water or carbon fluxes of plants and ecosystems. In particular oxygen isotopes (18O) in leaf water or plant organic material are now beginning to be established as a simple and integrative measure for transpiration. Current 18O models, however, are still limited in their application to a broad range of different species and ecosystems. It remains for example unclear, if species-specific effects such as different leaf morphologies need to be included in the models for a precise understanding and prediction of 18O signals. In a common garden experiment (Currency Creek Arboretum, South Australia), where over 900 different Eucalyptus species are cultivated in four replicates, we related differences in leaf water relations and leaf morphologies of 25 different species to 18O signals in leaf water. In particular, we determined for all species water potential, relative water content, apoplastic water fraction and stomatal conductance as well as leaf thickness, specific leaf area and weight. First analyses revealed that leaf water relations and leaf water 18O at steady state were related but significantly different among the investigated species. Fitting factors (effective path length) of leaf water 18O models were also significantly different among the investigated species but were related to species-specific physiological and morphological parameters. Our data suggest that leaf water 18O can act as powerful tool to estimate transpiration in comparative studies but that additional leaf morphological parameters need to be considered in existing 18O models for increased accuracy.
Key words: stable isotopes, plant water relations, ecophysiology
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