Hydraulic traits of Juniperus communis L. along elevations and European populations

Plant hydraulics play an important role in determining plant distribution and performance, by influencing their growth and productivity. Knowledge of the hydraulic amplitude and plasticity of species is thus a prerequisite for estimating future performance under climate change. We investigated hydraulic safety and efficiency in Juniperus communis L. to estimate its intra-specific hydraulic variability. We analysed plants growing along an elevational transect (700-2000 m a.s.l., Tyrol, Austria) and plants grown in a common garden experiment from seeds collected in various European regions (France, Austria, Ireland, Germany and Sweden). Vulnerability to drought-induced embolism (i.e. hydraulic safety) was assessed via Cavitron and ultrasonic acoustic emission techniques while specific hydraulic conductivity (i.e. hydraulic efficiency) was measured with a flow meter. Hydraulic safety (water potentials inducing 12, 50 and 88% loss of conductivity) and efficiency did not differ significantly neither across elevations nor between European provenancies. Common juniper proved to a be a species with high resistance to drouht stress and showed surprisingly homogenous hydraulic traits, despite sub-species are formed at higher elevation and plant morphology differed widely across provenancies. Due to its overall high hydraulic safety, this species can be considered as less susceptible to the effects of a warmer climate.