Fig. 1 Mortality rate of oak (Quercus petraea ) and beech (Fagus sylvatica ) saplings at the end of a recovery growing season following a growing season with 4 drought duration treatment (D0 = watering weekly, D1 = watering biweekly, D2 = watering monthly, and D3 = watering bimonthly) combined with N-fertilization (1.68 g N kg-1 dry soil fertilized vs. unfertilized).
Fig. 2 Midday water potential (ψleaf) after two-month of drought treatment on 5 August 2018 (a, b), leaf net-photosynthesis (Aleaf) after two- (6 August 2018) (c, d) and four- (28 September 2018) (e, f) months of drought duration treatment in 2018, and the relative height increment (g, h) between 30 May (initial) and 1 October 2018 (after 4-months of drought treatment) for oak (Quercus petraea ) and beech (Fagus sylvatica ) saplings. D0 (watering weekly), D1 (watering biweekly), D2 (watering monthly), and D3 (watering bimonthly) represent the drought duration. Different letter indicates significant difference in parameters among D0, D1, D2, and D3.
Fig. 3 Non-structural carbohydrate (NSC) concentrations in leaves, shoots and roots of oak (Quercus petraea ) and beech (Fagus sylvatica ) saplings after four months of drought duration treatment in 2018 (pre-winter) and before the growing season 2019 (post-winter). D0 (watering weekly), D1 (watering biweekly), D2 (watering monthly), and D3 (watering bimonthly) represent the drought duration. Different letters indicate significant differences in parameters among D0, D1, D2, and D3.
Fig. 4 Over-winter changes in non-structural carbohydrate (NSC) concentrations (post-winter values minus pre-winter values) and the sugar/starch ratio in shoots and roots of oak (Quercus petraea ) and beech (Fagus sylvatica ) saplings treated with four drought durations during the previous growing season. D0 (watering weekly), D1 (watering biweekly), D2 (watering monthly), and D3 (watering bimonthly) represent the drought duration.
Fig. 5 Leaf net-photosynthesis (Aleaf) and relative height increment of oak (Quercus petraea ) and beech (Fagus sylvatica ) saplings treated with four drought durations in 2018 and well-watered in 2019. D0 (watering weekly), D1 (watering biweekly), D2 (watering monthly), and D3 (watering bimonthly) represent the drought duration. Different letters indicate significant difference in parameters among D0, D1, D2, and D3.
Fig. 6 2019 recovery growth rate (measured at the end-season 2019) in relation to pre-winter and post-winter NSC in shoots and roots of oak (Quercus petraea ) and beech (Fagus sylvatica ) saplings treated with four drought durations in 2018 and well-watered in 2019. In case there is a significant (p < 0.05) relationship between growth and NSC level for the pooled data, a fitting line is given.