DIGITALNA ARHIVA ŠUMARSKOG LISTA
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Since 2004, Slovakia has been involved in the rural development programs aimed at increasing of the habitats productivity, ensuring ecological stability in the upward climate change and better utilisation of the potential of the country to maximize CO2 sequestration (APA, 2015). An important tool is an afforestation of non-forest land (unsuitable for agricultural production or in the public interest associated with the greening of the landscape) by fast-growing species. At the same time, it increases the pressure on the use of woody biomass as a renewable energy resource. In the planning of economic exploitation of grey alder, it is necessary to find the productive optimum of species in the local conditions. Achievement of adequate quantity and quality of the production within the shortest possible time and reviewing the factors affecting the production represent a key moment in the decision-making. Knowledge gained from the analysis of grey alder natural populations pointed out differences in the production potential based on the rising altitude or the fluctuation of groundwater table (Douda et al., 2009; Rodríguez-González et al., 2010; Bugala and Parobeková, 2016). From the view of the ecological stability, in afforestation, it is necessary to use tree species in the zone of their ecological optimum, which does not necessarily coincide with their productive optimum. Trees growing in the ecological optimum are less sensitive to the external factors and their growth is evener (Pernar et al., 2012). Their ecological valence to the climatic changes is then much greater. This is very important for the local scale where forest management plans (e.g., tree species selection) and river engineering measures need to be established and adapted in order to mitigate global climate change (Rieger et al., 2017). Optimums consistency or determining of their priorities become an actual question. Dendroecological studies represent an appropriate solution to the mentioned scientific tasks (Bojaxhi and Toromani, 2016, 2017). They allow describing the dynamic of stand growth in the past by measuring the widths of tree rings or other parameters of increase and identify the climatic factors that control tree growth (Rozas et al., 2005). The main commonly monitored factors limiting the growth of woody plants are temperature and precipitation. The radial growth of tree is usually affected by temperatures and precipitation in the year of the growth as well as in the year preceding the formation of the tree ring (Speer 2010; Rybníček et al., 2012). Tree species often produce vessels at the beginning of the growing season before leaf-out, suggesting that these vessels develop from cambial derivatives from a favourable previous growing season that overwintered in an undifferentiated state (Speer, 2010). Direct influence of temperature on the growth mainly occurs at the beginning of the growing season when low temperature can postpone the beginning of the cambial activity. On the other side, existing research reveals, that alders are generally little sensitive to the precipitation in the current period due to nearby groundwater table (Bugala and Parobeková, 2016; Vacek et al., 2016). The conditions of root system may negatively depend on the precipitation of the previous periods, since high level of groundwater table causes its strong damage (Dittert et al., 2006; Rodriguez-Gonzales et al., 2010). This study is part of a long-term research of naturally occurring black and grey alder stands in Slovakia. The aims of the study are 1) to analyse the productive potential of grey alder along an altitudinal gradient 2) to verify coincidence of the productive and ecological optimum and 3) to identify the climatic factors that control the growth of grey alder. These findings are necessary for the purposes of forthcoming afforestation of non-forest land or for reforestation of the endangered areas. Material and methods Materijal i metode Site description – Područje istraživanja The study was conducted in the Great Fatra Mts belonging to the Western Carpathians (Figure 1). The data were |