Abstract
In angiosperms, many studies have described the inter-specific variability of hydraulic-related traits and little is known at the intra-specific level. This information is however mandatory to assess the adaptive capacities of tree populations in the context of increasing drought frequency and severity. Ten 20-year old European beech (Fagus sylvatica L.) provenances representing the entire distribution range throughout Europe and differing significantly in aboveground biomass increment (ABI) by a factor of up to four were investigated for branch wood anatomical, hydraulic, and foliar traits in a provenance trial located in Northern Europe. We quantified to which extend xylem hydraulic and leaf traits are under genetic control and tested whether the xylem hydraulic properties (hydraulic efficiency and safety) trades off with yield and wood anatomical and leaf traits. Our results showed that only three out of 22 investigated ecophysiological traits showed significant genetic differentiations between provenances, namely vessel density (VD), the xylem pressure causing 88% loss of hydraulic conductance and mean leaf size. Depending of the ecophysiological traits measured, genetic differentiation between populations explained 0–14% of total phenotypic variation, while intra-population variability was higher than inter-population variability. Most wood anatomical traits and some foliar traits were additionally related to the climate of provenance origin. The lumen to sapwood area ratio, vessel diameter, theoretical specific conductivity and theoretical leaf-specific conductivity as well as the C:N-ratio increased with climatic aridity at the place of origin while the carbon isotope signature (δ13C) decreased. Contrary to our assumption, none of the wood anatomical traits were related to embolism resistance but were strong determinants of hydraulic efficiency. Although ABI was associated with both VD and δ13C, both hydraulic efficiency and embolism resistance were unrelated, disproving the assumed trade-off between hydraulic efficiency and safety. European beech seems to compensate increasing water stress with growing size mainly by adjusting vessel number and not vessel diameter. In conclusion, European beech has a high potential capacity to cope with climate change due to the high degree of intra-population genetic variability.
Highlights
European beech (Fagus sylvatica L.) dominated the natural vegetation types of forests in Central Europe for centuries, forming large stands of resilient forest ecosystems (Ellenberg and Leuschner, 2010)
The field trial studied is part of the International Beech Provenance Trial Series 1993/1995 under EU funding (AIR3CT94-2091), which investigates the role of the genetic variation of beech for adaptability, productivity and selected ecosystem functions considering risks of global climate change
As all provenances were grown in a single environment, we were able to assess the genetic differentiations between provenances for several functional traits
Summary
European beech (Fagus sylvatica L.) dominated the natural vegetation types of forests in Central Europe for centuries, forming large stands of resilient forest ecosystems (Ellenberg and Leuschner, 2010). The Central European beech populations are expected to suffer high mortality rates probably altering the distribution range at its dry distributional limit as a consequence of increased physiological stress due to a higher risk of drought exposure associated with recent climate change. Despite an increasing amount of studies on functional traits which are known to be related to drought resistance in beech, e.g., leaf stomatal features (Stojnicet al., 2015), wood structure (Eilmann et al, 2014), resistance to xylem cavitation (Herbette et al, 2010, Wortemann et al, 2011), or hydraulic architecture (Aranda et al, 2015; Schuldt et al, 2016), still very little information is available on the relevance of phenotypic plasticity or genetic variation of traits on the adaptation of populations
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