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• Study of seepage water under pure and mixed stands of Douglas fir, spruce and beech. • Seepage water under beech: largest amount and lowest NO 3 , Ca, Mg, Al concentration. • Seepage water under Douglas fir: smallest amount. • Seepage water under Douglas fir at N-rich sites: high NO 3 , Ca, Mg, Al concentration. • Mixed Douglas fir–beech stands: good option concerning water quantity and quality. Norway spruce (Picea abies L.) has been a key tree species and timber source in European forests the last centuries and is increasingly suffering from drought and bark beetle infestations due to climate warming. Current management options include replacing of Norway spruce monocultures with pure and mixed stands of European beech (Fagus sylvatica) that is the naturally dominating tree species in Central Europe. Additionally, Douglas fir (Psudotsuga menziesii), a tree species with high water use efficiency and drought tolerance, is being increasingly cultivated to increase the resilience of European forests and meet the future demand of conifer timber in a warming climate. We studied the seepage water quantity and quality with a particular focus on the nitrate (NO 3 –) concentration and N leaching under pure and mixed stands of Douglas fir, Norway spruce, and European beech at seven sites in Germany. Additionally, we investigated seepage water concentrations of SO 4 -S, Ca, Mg, K, Al and hydrological variables (interception, canopy throughfall, transpiration). Looking at the seepage water quantity and quality, the best management option is the cultivation of pure beech stands. However, this is associated with the well-known risk of monocultures concerning ecosystem disturbance. Beech stands showed the highest seepage water quantities and the lowest seepage water concentrations of major cations and anions, including NO 3 –. Seepage water quantity was the smallest under pure Douglas fir compared to spruce and beech stands. The composition effects of stand tree species on seepage water quality and nutrient leaching were site-dependent. At N-rich sites, pure Douglas fir stands showed higher seepage water NO 3 – concentrations than spruce and beech stands, whereas the tree species effects were small at N-poor sites. With respect to seepage water quantity and quality, cultivation of mixed Douglas fir–beech stands is a promising option for producing conifer timber and at the same time avoiding increased disturbance risks of mono-species forests under a warmer climate. Our results support the recommendation of mixed Douglas fir–beech stands based on soil quality, ecosystem resilience, and forest economic studies. [ABSTRACT FROM AUTHOR]