Some ecophysiological stress indicators of pedunculate oak (Quercus robur L.) in the north easteren of Slovenia

Opazno sušenje in fiziološko pešanje doba (Quercus robur L.) je posebno izrazito v Prekmurju v zadnjem desetletju zaradi sušnega podnebja, neugodne razporeditve padavin in možnih hidromelioracijskih ukrepov. Prispevek obravnava povezavo med vodnim stresom in kazalci vodnih razmer (višina podtalnice, padavine, vodostaji rek Mure in Ledave) ter drugimi kazalci stresa(vodni potencial, električna prevodnost kambijeve cone, osutost krošnje)v gozdnem kompleksu Murska šuma na skrajnem vzhodu Slovenije, kjer stabili izbrani dve ploskvi z različno poškodovanostjo dobovih dreves. Tam smo mesečno določali vodni potencial, električno prevodnost kambijeve cone in osutost krošnje. Meritve so pokazale zvezo med vodnim potencialom in gladino podtalnice, ki je bila na ploskvi z bolj prizadetimi dobovimi drevesi večja, kot na ploskvi z manjšo prizadetostjo. Vzporedno s terenskimi opazovanji je potekal lončni poskus v kontroliranih pogojih na petletnih dobovih sadikah, opravljen v avgustu. Točka začetnega zapiranja listnih rež je bila v intervalu med -0,5 in -0,7 MPa, nepovratno zapiranje pa je povzročil vodni potencial pod (bolj negativen) -1,62 MPa.In the last decade in Prekmurje, there has been a noticeable decline and physiologically weakening of the pedunculate oak (Quercus robur L.) because ofdry climate, unfavourable precipitation patterns and human influence throughchanges in watercourses and the water table. The paper addresses the relationship between water stress of the common oak and indicators of water status in the Murska {uma forest complex (groundwater table, precipitation, water level of the rivers Mura and Ledava) using plant stress indicators such as water potential, electrical resistance of the cambial zone and crown defoliation. Ttwo permanent plots with varying levels in decline in pedunculate oak trees were chosen. Water potential, electrical resistance of cambial zone and defoliation were measured once a month. The measurements showed a relationship of considerable importance between the water potential and groundwater table, which was stronger on plot that showed more intensive decline. At the same time a pot experiment was carried out withfive year common oak seedlings to define water potential at wilting and permanent stomatal closure point. The wilting point was reached at values between -0,5 and -0,7 MPa and permanent stomatal closure was reached below -1,62 MPa