Fertilization regime interacts with fall temperature in the nursery to determine the frost and drought tolerance and nutrient status of the Mediterranean oak Quercus ilex L.

Abstract

Nitrogen fertilization in the nursery usually improves the transplanting performance of Mediterraneanoaks. However, high N fertilization can reduce seedling stress tolerance, probably depending on the environmentalconditions under which plants grow. We hypothesize that high N fertilization under mild fallconditions reduces cold and drought acclimation. To assess this hypothesis, we studied if fall temperaturedifferences among cultivation locations influence the effect of N fertilization regime on cold and droughttolerance, N status and growth in the evergreen Mediterranean oak Quercus ilex subsp. ballota (Desf.) Samp.Plants were cultivated in two nurseries of distinct fall temperature conditions (mild and cold fall nurseries)under four fertilization regimes: Low and highNat constant rate (total N, 33 and 175 mg seedling 1), highNat exponential rate (175 mg N seedling 1) and fallNloading (89 mg N seedling 1). Seedling water relations,survival to a 12 C frost and leaf soluble carbohydrates concentration were assessed three times in the fall,and shoot elongation was measured weekly through the fall. Moreover, seedling mass and N concentrationwere measured at the end of the fall. Fall loaded seedlings had the highest tissue N concentration, whileseedling mass was highest in the highNconstant and exponential fertilization regimes. Seedlings at the coldfall nursery concentrated moreNbut were smaller than seedlings at the mild fall nursery.