Pre-dawn water potential and nutritional status of pedunculate oak (Quercus robur L.) in the north-east of Slovenia

In the 1997 growth period monthly measurements of pre-dawn water potential, electrical resistance of the cambial zone, groundwater level and quality t ogether with annual dynamics of macronutrive elements in leaves and heavy m etals (Zn, Ph, Cd) were performed. Two plots having different groundwater t ables and crown defoliation were studied in the pedunculate oak forest comp lex (Querco Roboris-Carpinetum M. Wraber) in the north-east of Slovenia. Re sults showed lower (more negative) values of pre-dawn water potential and h igher values of cambial electrical resistance on the plot with greater crow n defoliation, which also had a lower groundwater table. Groundwater seems to be the key factor in the process of oak decline.