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Title: Leaf hydraulic vulnerability to drought is linked to site water availability across a broad range of species and climates

item BLACKMAN, CHRIS - Western Sydney University
item Gleason, Sean
item CHANG, YVONNE - Macquarie University
item COOK, ALICIA - Macquarie University
item LAWS, CLAIRE - Macquarie University
item WESTOBY, MARK - Macquarie University

Submitted to: Annals Of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2014
Publication Date: 7/1/2014
Citation: Blackman, C.J., Gleason, S.M., Chang, Y., Cook, A., Laws, C., Westoby, M. 2014. Leaf hydraulic vulnerability to drought is linked to site water availability across a broad range of species and climates. Annals Of Botany. doi: 10.1093/aob/mcu131.

Interpretive Summary: Species’ distributions across the world are limited by climate. For example, palm trees are restricted to warm regions of the earth, whereas conifers are largely restricted to cold regions of the earth. Growing productive crop plants outside their ideal climate envelope (suitable range of climate) could improve agricultural productivity. Additionally, understanding the effects of climate change on the distributions of naturally-occurring (wild) plant species is also a priority for research. However, before meaningful progress can be made towards these goals it is desirable to first understand exactly how the functioning of plants is affected by climate. This study investigated the relationship between climate aridity (how hot and dry the climate is) and the ability of plants to transport water through their leaves. We hypothesized that plants restricted to dry portions of the earth should possess water transport systems (leaf xylem) that resist failure when subjected to aridity, whereas plants restricted to wet regions of the earth should possess water transport systems that are more susceptible to failure when subjected to aridity. We found that the sensitivity of leaf xylem (part of the plant’s water transport system) was strongly related to climate and could be used to predict with reasonable certainty (about 70% of the differences in xylem sensitivity was aligned with aridity). These results suggest that the vulnerability of leaf xylem to aridity is likely an important trait allowing plants to survive in arid environments. As such, improving leaf xylem in plant breeding programs may improve crop performance in more arid environments. Additionally, measurements of leaf xylem may help scientists predict how species’ distribution patterns might change in response to changes in climate.

Technical Abstract: Background and Aims: Vulnerability of the leaf hydraulic pathway to water-stress-induced dysfunction is a key component of drought tolerance in plants and may be important in defining species’ climatic range. However, the generality of the association between leaf hydraulic vulnerability and climate across species and sites remains to be tested. Methods: We measured leaf hydraulic vulnerability to drought (P50leaf; the water potential inducing 50% loss in hydraulic function) in a diverse group of 92 woody angiosperms from sites across a wide range of habitats. These new data together with some previously published were tested against key climate indices related to water availability. We also examined differences in within-site variability in P50leaf between sites. Key Results: Values of hydraulic vulnerability to drought in leaves decreased strongly (i.e. became more negative) with decreasing annual rainfall and increasing aridity across sites. The standard deviation in P50leaf values recorded within each site was positively correlated with increasing aridity. P50leaf was also a good indicator of the climatic envelope across each species’ distributional range as well as their dry-end distributional limits within Australia, though this relationship was not consistently detectable within sites. Conclusions: Our findings indicate that species sorting processes have influenced distributional patterns of P50leaf across the rainfall spectrum, but alternative strategies for dealing with water deficit exist within sites. The strong link to aridity suggests that leaf hydraulic vulnerability may influence plant distributions under future climates.