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ŠUMARSKI LIST 5-6/2019 str. 38     <-- 38 -->        PDF

per hectare in primary productivity so that it can reach 662 m3 in hectare at the age of 100 (Carus, 1998). Beechwood has been classified as a moderate-intensity (0.66 g/ cm³) wood. As a hardwood tree species, its wood is heavy, hard, strong and very resistant to shock. For this reason, it is suitable for steam-bending. The oriental beech tree is mainly used as firewood, but there are also other uses of it, such as particleboard, furniture, parquet, masts, traverse manufacturing, and paper. In general, Oriental beech has a similar appearance to European Beech (Fagus sylvatica) (Kandemir and Kaya, 2009). The determination of silvicultural treatments that need to be applied to obtain the highest quality and quantity of products in oriental beech forests and to benefit from plantation areas at the highest level is an important subject of forestry.
Strong thinning suitable for the biology of beech was performed while thinning treatments were applied. Strong thinning is frequently used in Central European Forestry. It is based on Schädelin (1942) principles. Firstly, positive selection is performed at a relatively early time in the development of stand where final crop trees are selected and competition is removed. Future trees are selected for the thinning of the stand and should be distributed as orderly as possible. Abetz (1975) developed various selective thinning methods in which the first thinning procedures are performed and final crop trees are selected for young plants. Busse (1935) then initiated the concept of group selection thinning developed by Kato (1973) in which an aggregation or a small tree group was addressed as an individual plant tree. Reininger (1993) developed a structural thinning that creates thinned stands.
Many studies focused on the effects of thinning on stand parameters and compared the thinned and untreated (control) stands (Bryndum, 1987; Hasenauer et al. 1996; Sharma et al. 2006; Spellmann and Nagel, 1996) or those with different thinning intensities (Guericke, 2002; Juodvalkis et al. 2005; Sanchez-Gonzalez et al. 2005; Utschig and Kusters, 2003). Similarly, the effects of different thinning regimes on stand value were also examined (Förster, 1993; Hasenauer et al. 1996; Kato and Mülder, 1998). Furthermore, the effects of different types of selective thinning, group selective thinning (Kato and Mülder, 1998), and early and late thinning results were studied (Henriksen and Bryndum, 1989; Klädtke, 2001). According to Schädelin (1942), Leibundgut (1982) and Schütz (1987), classical selective thinning is characterized by the repetition of the selection of future trees, and their number is reduced from the beginning of selection to the final thinning performed in the optimal phase. This means that the average distance between future trees increases in a period from the first thinning to the final thinning (Boncina et al. 2007).
Although the above-ground productivity of natural forests usually varies by the stand age, it tends to decrease after closure is provided (Ryan et al. 1996). For this reason, many ecologists and foresters have attempted to keep such changes under control in order to improve tree growth and wood quality (Macdonald et al. 2010). Among controlling methods, thinning treatment is considered as an important and effective way of managing forest growth and productivity (Roberts and Harrington, 2008). Thinning treatments, which are an integral part of intensive forestry activities, constantly improve the quality of stands by cleaning up slow-growing, damaged or unhealthy trees (Zeide, 2001). The productivity of stands treated by this method is improved, and then larger and higher quality trees are obtained (Nishizono, 2010). In broad-leaved stands, thinning can produce large-diameter trees, can improve the stem quality, can increase the variable volume and yield value and can shorten the management time (Hibbs et al. 1989; Mayor and Rodà, 1993; Cameron et al., 1995; Nowak, 1996; Oliver and Larson, 1996; Miller, 1997; Medhurst et al. 2001; Juodvalkis et al. 2005; Rytter and Werner, 2007). In broad-leaved tree species, the purpose of thinning is usually to increase the quality of the final product (Savill et al. 1997). Stem size and quality are the decisive criteria for valuable timber production. Forestry practices and especially thinnings are important for high-quality wood production. It is well known that thinning has a significant influence on forest growth and productivity (Utschig et al. 2003; Spiecker, 1996; Boncina and Kadunc, 2007). To decrease the number of trees by performing thinnings in the stand may change the ecological conditions in the forest. One of the most important effects of thinning in the forest ecosystem is that the light-temperature-moisture change affects the litter decomposition, and thus, nutritional elements get into the forest soil and these nutritional elements make soils rich (Makineci, 2004). Although highly competitive trees are much more sensitive to the changes in water balance, the restriction of growth by water and the nutritional source is reduced by thinning (Pretzsch, 2005). Therefore, the aim of this study is to determine the effects of thinning intensity on the growth and increment of oriental beech in plantation areas established in different growing environments.
MATERIAL AND METHODS
MATERIJALI I METODE
Study Area – Podruèje istraživanja
Experimental plots were chosen from young oriental beech plantation areas which are within the boundaries of Vakfıkebir and Maçka districts of Trabzon province. The locations of experimental plots are presented in Figure 1.