Intra-annual variations in leaf development, radial growth, including the phloem part, and sap flow have rarely been studied in deciduous trees from drought-prone environments. In order to understand better the chronological order and temporal course of these processes, we monitored leaf phenology, xylem and phloem formation and sap flow in Quercus pubescens from abandoned karst grasslands in Slovenia during the growing season of 2014. We found that the initial earlywood vessel formation started before bud opening at the beginning of April. Buds started to open in the second half of April and full leaf unfolding occurred by the end of May. LAI values increased correspondingly with leaf development. About 28 % of xylem and 22 % of phloem annual increment were formed by the time of bud break. Initial earlywood vessels were fully lignified and ready for water transport, indicating that they are essential to provide hydraulic conductivity for axial water flow during leaf development. Sap flow became active and increasing contemporarily with leaf development and LAI values. Similar early spring patterns of xylem sap flow and LAI denoted that water transport in oaks broadly followed canopy leaf area development. In the initial three weeks of radial growth, phloem growth preceded that of xylem, indicating its priority over xylem at the beginning of the growing season. This may be related to the fact that after bud break, the developing foliage is a very large sink for carbohydrates but, at the same time, represents a small transpirational area. Whether the interdependence of the chronological sequence of the studied processes is fixed in Q. pubescens needs to be confirmed with more data and several years of analyses, although the correct sequence of processes is essential for synchronized plant performance and response to environmental stress.
COBISS.SI-ID: 4701350
Our research focused on the influence of climatic factors on wood-anatomical features of pubescent oak (Quercus pubescens Willd.), which is one of the dominant native tree species in Slovenian sub-Mediterranean climate. In the period 2009-2014 we studied relationship between various wood-anatomical parameters (xylem ring width, early- and latewood widths, diameter, area and number of earlywood vessels) and climatic factors (precipitation, temperature and soil water content). In addition, we checked whether the studied wood-anatomical parameters contained complementarity or redundant climatic information in pubescent oak at Podgorski Kras. Preliminary results showed that studied parameters were mainly related to temperature. In period before and at the onset of cambial activity (i.e. January-May), earlywood width and earlywood vessel area were positively related to the maximum temperature, whereas number of earlywood vessels and xylem ring width were positively related to the mean temperature. This indicates that weather conditions in this period have a significant impact on hydraulic properties of xylem. For latewood width, we found significant correlation with temperature in summer months and for earlywood vessels with the temperature in period January-April. We could not confirm the impact of precipitation on xylem ring development. We concluded that latewood width and earlywood vessel characteristics are promising wood-anatomical parameters containing complementary information on the impact of weather conditions on radial growth of pubescent oak. However, it is necessary to emphasize that our analysis has been performed in a relatively short time period, therefore long-term data are needed for more reliable assessment of the applicability of the selected wood-anatomical parameters to dendroclimatological studies.
COBISS.SI-ID: 4637094