Xylem traits and water-use efficiency of woody species co-occurring in the Ti Tree Basin arid zone
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Species with low density of intact branches are likely to have higher growth rates than species with high density of intact branches, but at the cost of a lower water-use efficiency and larger sensitivity to xylem embolism.
The hydraulic niche separation theory proposes that species co-exist by having a range of traits to allow differential access to resources within heterogeneous environments. Here, we examined variation in branch xylem anatomy and foliar carbon stable isotopes (δ13C) as a measure of water-use efficiency (WUE) in seven co-occurring species, Acacia aneura, Acacia bivenosa, Corymbia opaca, Eucalyptus camaldulensis, Erythrina vespertilio, Hakea sp., and Psydrax latifolia, in an arid zone open Corymbia savanna on the Ti Tree Basin, Northern Territory, Australia. We test the following hypotheses: (1) Species with large conductive areas exhibit a low density of intact branches, while species with small conductive areas have a significantly higher density of intact branches. (2) Species with smaller conductive areas exhibit more enriched values of δ13C and therefore have larger WUE than those with larger conductive areas and (3) there is an inverse correlation between theoretical sapwood hydraulic conductivity and vessel implosion resistance. The results of this study demonstrated significant variation in density of intact branches, ranging from 0.38 to 0.80 g cm−3 and this variation was largely explained by variation in sapwood conductive area. Species with low conductive areas (P. latifolia, Hakea sp. and Acacia species) exhibited large values of WUE (r 2 = 0.62, p < 0.05). These species are likely to be less vulnerable to cavitation by having small conductive areas and thicker fibre walls. We demonstrated a significant (r 2 = 0.83, p = 0.004) negative correlation between theoretical sapwood hydraulic conductivity and vessel implosion resistance. These results are discussed in relation to hydraulic niche separation.
KeywordsWood anatomy Hydraulic niche separation Arid zone Water-use efficiency Carbon isotopes
We would like to thank the Endeavour Fellowships Scope Global, Australia for financial support (Grant number ERF_PDR_4065_2014). We also thank Dr. Sebastian Pfautsch from the University of Western Sydney. Jacqueline Loyola-Echeverría, Dr. Rachael Nolan and Tonantzin Tarin-Terrazas from the University of Technology Sydney, Dr. Nele Schmitz from the École Normale Supérieure de Lyon and Dr. Kasia Ziemińska from Macquaire University for laboratory assistance and advice during the planning and development of this study. This work was also supported by an ARC grant (DP140101150) awarded to Derek Eamus.
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Conflict of interest
The authors declare they have no conflict of interest.
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