Intraspecific variations in drought response and fitness traits of beech (Fagus sylvatica L.) seedlings from three provenances differing in annual precipitation

Climate change predictions forecast extended drought periods, which are expected to pose an enhanced risk to forest trees. Here, we investigated the drought response and fitness traits in European beech (Fagus sylvatica L.) in response to a severe progressive drought. The capability of three beech provenances from habitats differing in annual precipitation (544, 665, and 766 mm year(-1)) to cope with drought was compared in a common garden experiment using beech seedlings. Soil and plant water status, maximum quantum yield of PSII, growth and biomass partitioning, stomatal conductance, and transcript abundance pattern of the kinase, Open Stomata 1 (OST1), of control (well-watered) and drought-treated (water withheld) plants from each provenance were repeatedly measured during a 60-day drought experiment. The lowest precipitation provenance displayed a more isohydric phenotype with a prompt stomatal closure, increased OST1 levels, high water potential and leaf water content, and a decrement in the maximum quantum yield of PSII. The other two provenances showed a more anisohydric stomatal regulation with a slow and delayed stomatal closure and a decrease in the water status. These findings suggest that intraspecific variations in beech for diverging drought resistance strategies exist and might be mediated by differences in the abscisic acid signaling pathway. The higher precipitation provenance maintained high quantum yield of PSII, and water potentials above -2.0 MPa for a longer period of time than the other two provenances, and consequently, mortality was delayed in this provenance. We concluded that lower precipitation adapted plants employ a drought resistance strategy suitable for the moderate drought, whereas the higher precipitation habitat plants revealed mechanisms, which could be better suited to cope with more severe drought events.