Within species diversity of transpiration efficiency in two white oak species
Résumé
Trees are a major component of the biosphere. Covering many regions of the world as natural forests or plantations, they take an important role in the balance of the ecosystems. Recent studies has shown that some of these ecosystems may already be responding to climatic warming and drought, two main consequences of climate change. Such changes have been hypothesized to be able to impact the WUE (defined as the ratio between carbon assimilation during photosynthesis and the stomatal conductance for water at the leaf level) of forest ecosystems. In such context we focused on the diversity of WUE in two major French oak species : Quercus robur L. and Quercus petraea (Matt.) Liebl. These two species are largely sympatric however with different ecological requirements. While Q. petraea is more frequently found on well drained soils and is more tolerant to drought, Q. robur is able to survive and grow on poorly drained soils being the result of a higher tolerance to water-logging (Becker et al. 1982). A few comparative studies have described Q. petraea as more efficient than Q. robur the later having lower values of leaf level WUE (Ponton et al. 2001, Pflug et al. 2015, Thomas et al. 2000) however these results are not consistent in the literature since other studies showed similar WUE between the two species (Parelle et al. 2016, Hu et al. 2013) or even higher WUE for Q. robur (Rasheed-Depardieu 2015). Moreover to our knowledge no comparative studies between the two oak species focused on the transpiration efficiency (TE) (defined as the ratio between total biomass production and total water consumption at the whole plant level) have been conducted, leaving a huge gap on the subject. Therefore we addressed the following questions: Do the differences in WUE at the leaf level result in similar differences at the whole plant TE? Which underlying morphological and physiological traits are related to these differences between species but also which traits are driving the within-species diversity? Hence, in a comparative study between the two oak species we assessed different levels of WUE as well as underlying traits for control and drought plants.
References
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