Matjaž Čater, Tom Levanič
Physiological and growth response of Quercus robur in Slovenia
Dendrobiology 2015, vol. 74: 3-12
Pedunculate oak (Quercus robur L.) forests in Slovenia are experiencing widespread mortality. Changes in lowlands reflect in decline of complete forest complexes, high mortality, uneven stand structure and associated forest regeneration problems. Prediction of the present-tree response in disturbed forest ecosystems may significantly contribute to better guideline policies for the silvicultural and forest management practice in the changing environment in both stressed and stabile forest ecosystems. On pedunculate oak floodplain site two groups of vital and declining trees were selected according to the ICP methodology. During three consequent vegetation periods (2006, 2007 and 2008), ecophysiological response of trees in controlled conditions (maximal photosynthetic rates – Amax, water conditions) were recorded and compared with radial growth (tree ring width, pointer years). Growth was compared with meteorological data from closest meteorological stations to recognize and define tree response to changing growing conditions in all groups. Significant differences in light response (Amax) between declining and vital trees were observed as well as in water use efficiency (WUE) and in pre-dawn water potential (Ψpd). Beside the differences in tree-ring width, a significant difference in the year-to-year variability of tree-rings between both studied oak groups was confirmed. Vital oaks in floodplains responded positively to above average precipitation in May and June, while declining oaks with very narrow rings, usually consisting of only one row of vessels, responded negatively to above average temperature in March.
Additional key words: Pedunculate oak, growth, tree-ring width, photosynthesis, water stress, lowland forests, climate response