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ŠUMARSKI LIST 5-6/2018 str. 44     <-- 44 -->        PDF

Seed orchards serve as the link between tree breeding and afforestation (Kang 2001, Funda and El-Kassaby 2012). First planned tree breeding activities began in Turkey in 1964 (Urgenc 1967). In these studies, pine species were given priority, and the acquired knowledge and experience led to the establishment of the first commercial seed orchard for Turkish red pine (Pinus brutia Ten.) species in 1976 (Alan 2012).
Turkish red pine is the most important coniferous tree among the forest tree species of Turkey. It is a characteristically fast-growing and widely distributed species, also the most commonly used species in wood production and afforestation in Turkey. In this respect, it has also been defined as one of the preferred and prioritized species for tree breeding in the National Tree Breeding Program, which was first implemented in 1994 (Koski and Antola 1993). The aim of this Breeding Program is to use seed orchards to meet the seed requirements of afforestation activities. In this context, since the first seed orchard was established in 1976, the total area of Turkish red pine seed orchards has reached 615 hectares, 75 hectares of which were established through progeny trials (Bilgen et al. 2013; Oatiam 2015).
Seed orchards are considered to be an affordable tool that allows forest areas – and hence the quantity of forest products – to be increased over time (Codesido and Fernandez-Lopez 2014). Seed orchard management comprises various practices employed at seed orchards to produce the genetically and physiologically high-quality seeds that are necessary for establishing forests (Bramlett 1991; Codesido and Fernandez-Lopez 2014). While various tools can be used in seed orchard management, top pruning is a management tool that enables the relatively easy and safe collection of seed by reducing the heights of trees (Matheson and Willcocks 1976; Kajba et al. 2007; Funda and El-Kassaby 2012; Miller and DeBell 2013).
Top pruning which is the practice of removing whole tops or large branches by cutting reduces the heights of individual trees at a seed orchard, allowing them to receive more light. The greater amount of light received by ramets increases the ratio of Carbon: Nitrogen, which in turn increases the level of seed production (Sweet 1975). Top pruning may also facilitate tasks such as seed collection, pest control, and supplemental pollination activities (Gerwig 1987; Stoehr et al. 1995; Almqvist and Jansson 2015).
As Turkish red pine has been the most widely used species for afforestation in Turkey, Turkish red pine seed orchards have always been given the highest priority and importance. To collect information on the efficient management of Turkish red pine seed orchards,to date a number of studies have been conducted on top pruning (Sengun and Semerci 2002) and GA4/7 (Gibberellic acid) application (Ozturk et al. 2005).
In Turkey, seed orchards are still being established based on the results of progeny trials, and this leads to the constant formation of young seed orchards (Alan 2012). There are no studies on the effect of pruning on young and middle-aged Turkish red pine seed orchards.
While seed production naturally begins when the Turkish red pine seed orchards are seven-year-old, seed collection becomes more difficult in the ensuing years as the heights of the trees increases. An investigation of cone and seed production data over ten-year periods revealed that seed production per hectare in Turkish red pine seed orchards begins to decline after 20 years (Alan et al. 2011). This decrease is thought to be caused by two underlying reasons: Firstly, as the ramets in the seed orchard become fully developed, their branches cover all the empty spaces, decreasing the quantity of light the trees receive, and thus reducing the quantity of seed produced. Secondly, even though seed production levels remain relatively high, the increasing heights of the trees gradually makes it more difficult to collect the cones, preventing all the cones from being harvested, resulting in a certain quantity of cones being left on the trees. It has been suggested that severe and heavy top pruning (where more than four years growth is cut) might be a solution when it becomes difficult to collect cones due to the excessive growth of the trees in a seed orchard (Stoehr et al. 1995; Smith 2004). Alan et al. (2011) reported that by 2008, the area of Turkish red pine seed orchards aged 15 years or older had reached 75% of the total seed orchard. This has led to a need to examine the effects of intense top pruning on seed orchards aged 15 years or more. To enhance the diminishing cone production in middle-aged and old Turkish red pine seed orchards, information is required on the effects of top pruning in young orchards. In this context, study was implemented in 2008 on old, middle-aged and young seed orchards. As a continuation of that study, top pruning was repeated in middle-aged and young seed orchards in 2012, while the old seed orchard was not pruned.
This study aimed to (a) asses the development (height, diameter at breast height and volume index) of pruned and unpruned ramets, (b) compare pruned and unpruned ramets in terms of conelet, which is considered immature cone, and cone, which contains seeds for reproduction of species productivity, and (c) use the obtained information on productivity and ramet development for the management of seed orchards.
Three Turkish red pine seed orchards with different age groups (young, middle-aged and old orchards) were included in this study (Table 1). When the study was initiated in 2008, seed production had not yet begun in young seed