Memory Effects of Water Deprivation in European Beech (Fagus sylvatica L.) and Silver Fir (Abies alba Mill.) Seedlings Grown in Mixed Cultivation

Very limited information is available on the drought tolerance of European beech and silver fir in mixed cultivation, both for mature forests and natural regeneration. Particularly, little information is available regarding the significance on memory effects of drought exposure. Therefore, drought memory was analyzed in seedlings of these species grown in mixed cultivation in the present study. The results showed that previous-year drought hardening mediated enhanced biomass accumulation of beech leaves and root in the subsequent year, but did not impact fir growth. Total carbon (C) content was decreased by drought hardening in both the leaves and roots of beech and previous-year needles and roots of fir, in beech probably as a consequence of increased growth. Previous-year drought hardening had no significant effect on relative water contents, total nitrogen (N), or soluble protein contents in leaves and roots of beech and fir, but resulted in decreased total amino acid contents of beech leaves and fir needles. It further reduced structural N in current-year fir needles and decreased C/N ratios in roots of both beech and silver fir seedlings. Generally, the number of interspecific neighbors had no considerable effect on biomass or total C or N contents, as well as N partitioning in leaves and roots of beech and fir seedlings. The present study highlights that drought hardening induces memory effects in European beech and silver fir seedlings in their mixture in the subsequent year of growth, but these memory effects are stronger in beech than in fir.