Do ring-porous oaks prioritize earlywood vessel efficiency over safety? Environmental effects on vessel diameter and tyloses formation

•Tylose formation in current-year vessels varies along with drought severity.•Under drier conditions, ring-porous oaks show larger vessels and more tyloses.•Tyloses are less frequent for the more drought tolerant Quercus pyrenaica.•Quercus robur has narrower earlywood vessels but wider latewood increments.