Water status, nutrients and radial increment of pedunculate oak (Quercus robur L.) in northern Serbia and comparison with selected sites in Slovenia

Two adult oak tree groups in northern Serbia, differing in degree of decline, were studied. Measurements of pre-dawn water potential (PWP), nutrient status and radial growth were performed and compared with similar sites in Slovenia. In spite of favourable water conditions and sufficiently high groundwater table, values of PWP between groups were statistically significant, with lower values in the degraded group. Growth and nutrient analysis confirmed differences between the groups, while values of PWP did not indicate water stress. Higher values of foliar nitrogen in Serbia compared to similar sites in Slovenia may be connected with more intensive agricultural land use and, consequently, faster turnover. The different vitality status and variable nutrient content may also be due to disturbances in the functioning of the root system and impaired uptake ability.