THE EFFECTS ON THE SOIL NUTRIENT CONTENT OF DOUGLAS FIR AND KAZDAGI FIR IN CANGAL FORESTS IN AYANCIK, SINOP, TURKEY

The aim of the study was to compare the influence on nutrient pool in the soil of Douglas fir (Pseudotsuga menziesii (Mirb.) Franco), as exotic fast growing species, and Kazdagi fir (Abies normanniana subsp. equi-trojani (Asch.&Sint. ex Boiss) as native species. The study was conducted within a single stand, Cangal forest in Ayancik, Sinop located western Black Sea Region, the first plantation site in Turkey, in order to reduce variation in abiotic factors. Soil samples were collected from two different sample areas belonging to each species from natural Kazdagi fir and Douglas fir stands and each sample was taken from three different points and two levels (0-15 cm and 15-30 cm). C and N elements were analysed using de mental analyser, and basic macro and micro elements were determined by using TurboQuant-Powders N method as a percentage with XRF. According to the results of the variance analysis, the factors of tree species and soil depth are found to be affecting N, C and ZnO (F=9.038**; F=9.294***; F=2.476**) significantly. However, there is no significant effect on the other 26 nutrients. Strong positive and negative correlations were found between many nutrients. In the upper soil at 0-15 cm, N was determined to be higher compared to both the lower soil under Douglas fir stand and the Kazdagi fir stand. Douglas fir has a nitrogen increasing effect on soil content. With further research the research question should be questioned in relation to stand characteristics and growth based on long-term observations and measurements.