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ŠUMARSKI LIST 11-12/2021 str. 52     <-- 52 -->        PDF

INTRODUCTION
UVOD
Sycamore maple (Acer pseudoplatanus L.) produces economically attractive timber, offers ecological services and has high land compatibility, but is only a small component of European forests (Vacek et al. 2018). Despite its potential economic and ecological significance (Spiecker et al. 2009), the share of the sycamore maple generally does not exceed 3% by most national inventories in Europe (Hein 2009). This low stand volume is due to the fact that the sycamore maple tree rarely forms pure forest stands (Jones 1945; Hein et al. 2009). In Turkey, it spreads around 1000 meters in the Black Sea coastal forests of Thrace (Gültekin 2007). Yalt&305;r&305;k (1971) stated that this species does not have a natural distribution area in Turkey, but it comes artificially.
As a result of the rapid increase of the world population and the expansion of the global economy, the pressure on natural resources is increasing day by day. As in many countries, a large part of the forests in Turkey have been damaged due to various reasons (climate change, fragmentation, social pressure and etc.) and forests could not provide the required benefits in terms of both quantity and quality. Moreover, since the decrease in forest areas as a result of rapid population growth will increase the need for wood raw material in the future, more forest areas and therefore planned afforestation works are needed for supplying increasing wood raw material demand and to prevent air, land and water pollution caused by industrialization (Ürgenç 1998).
Afforestation works are mostly established for various purposes such as water and soil protection, wood production and carbon sequestration The effects of recent afforestation activities on biological diversity are also discussed. It is stated that the priority in afforestation studies is the need to protect the natural plant taxa in the area (Bremer and Farley 2010). Many researchers stated that sycamore increases biodiversity and ecological stability of forest ecosystems (Binggeli 1993; Pommerening 1997; Bell 2009) and it is soil-improving tree species that increased humus formation and nutrient cycling (Weber et al. 1993; Heitz and Rehfuess 1999). So, it is possible to say sycamore has an important potential to respond to projected future climate change (Kölling 2007; Hein et al. 2009). On account of, the species has value for both the forest sector and the wood processing industry especially in Central Europe (Spiecker et al. 2009; Thies et al. 2009; Vacek et al. 2018).
Maple seeds, which are in the category of orthodox and recalcitrant seeds during germination, may differ from species to species (Gültekin 2007). Seeds of maple species are considered by most researchers as seeds with germination barriers (Bradbeer 1988; Derkx 2000; Piotto et al. 2001; Gleiser et al. 2004; Zasada and Strong 2008). Although pericarp, seed coat and embryo dormancy are seen in maples, there are differences between species in terms of morphological and physiological dormancy (Young and Young 1992). Depending on the dormancy types, there are different techniques for romoving dormancy in Acer ssp. seeds. Cold-moist stratification is the widely used method for removing dormancy in many Acer species (Farmer and Cunningham 1981; Tylkowski 1995; Tremblay et al. 1996; Savage et al. 1998; Bourgoin and Simpson 2004; Gültekin 2007; Farhadi et al. 2013; Erdo&287;an Genç and Üçler 2020a; Erdo&287;an Genç and Üçler 2020b). In addition, gibberellic acid also promotes removing seed dormancy and stimulates seed germination in many species (Chen and Chang 1972; Beyhan et al. 1999; Phartyal et al. 2003a; Drãghici and Abrudan 2010; Stejskalová et al. 2015; Kumar et al. 2017).
Seeds usually respond to a combination of different environmental factors such as light, temperature and soil moisture that best suit their structure (Baskin and Baskin 1998). Germination occurs at a certain thermal rate, so temperature is the determining factor for germination and is directly related to the ecological characteristics of the species (De Castro and Hilhorst 2004). For most species, the prevailing soil temperature determines both the growth and germination rate of the seeds (Heydecker 1977).
Main goals of the study are (1) to investigate the effects of cold-moist stratification, sowing time and sowing environment (greenhouse and nursery) on the germination ability of the sycamore maple seeds, (2) to determine the best suitable climate factors for better germination ability and (3) to create basis knowledge for the further studies in terms of mass seedling production.
MATERIAL AND METHODS
MATERIJALI I METODE
Seed material – Sjemenski materijal
Seeds harvested from a single sycamore maple tree which is located in the Kanuni campus of Karadeniz Technical University (40059’47” N; 39046’20” E) were used as material. Altitude of the location of the single seed family above sea level is approximately 100 meters and the exposure is north. The seeds were harvested in September 2017.
Seeds were collected by hand from the middle-inner part of the crown of the seed family. Collected seeds were cleared from branches, leaves and stems in laboratory. After cleaning and the visually injured or damaged ones of the seeds were removed, the extracted seeds without wings were air-dried (10% seed moisture content). The flotation method was applied by using 96% ethanol in order to separate healthy seeds. 400 (4x100) seeds were used to determine the fullness rate. By using 800 (8x100) seeds, the mean 1000 Kernel Weights (g) of the seeds were determined according to ISTA (1996). Mean 1000 Kernel Weights (g) of the harvested seeds