European beech (Fagus sylvatica L., hereafter beech), one of the major native tree
species in Europe, is known to be drought sensitive. Thus, the identification of critical
thresholds of drought impact intensity and duration are of high interest for assessing
the adaptive potential of European beech to climate change in its native range. In
a common garden experiment with one-year-old seedlings originating from central
and marginal origins in six European countries (Denmark, Germany, France, Romania,
Bosnia-Herzegovina, and Spain), we applied extreme drought stress and observed
desiccation and mortality processes among the different populations and related them to
plant water status (predawn water potential, 9PD) and soil hydraulic traits. For the lethal
drought assessment, we used a critical threshold of soil water availability that is reached
when 50% mortality in seedling populations occurs (LD50SWA). We found significant
population differences in LD50SWA (10.5–17.8%), and mortality dynamics that suggest
a genetic difference in drought resistance between populations. The LD50SWA values
correlate significantly with the mean growing season precipitation at population origins,
but not with the geographic margins of beech range. Thus, beech range marginality may
be more due to climatic conditions than to geographic range. The outcome of this study
suggests the genetic variation has a major influence on the varying adaptive potential of
the investigated populations.