Investigation of relationships between some ecological factors and the growth of pure oriental spruce (Picea orientalis (L.) link) forests at different sites

In this study, physiographic, climatic and edaphic factors affecting the productivity (site index) of oriental spruce (Picea orientalis (L.) Link.) growing on seaward slopes in Eastern Black Sea Region were investigated. With this aim, 162 sample plots were taken in three forest sites (Canik-Giresun Mountains, Trabzon Mountains and Rize-Kaçkar Mountains). These plots were located within Dr. Kantarcı?s designated boundaries. In every sample plot, physiographic features such as latitude, longitude, elevation, inclination, aspect and distance to the ridge; and stand characteristics such as stand age and top height were determined. Site index of oriental spruce stands were calculated using stand age and top height. Also a soil pit was dug and samples were taken by depth (0-15, 15-30, 30-50, 50-80 and >80 cm) in every sample plot. Some physical and chemical properties of soil were examined. The climate type was found as very humid according to Thornthwaite, therefore, there was no water deficiency in the study area. Simple correlation was used to determine the relation between site factors and site index (site productivity). Multiple linear regression and regression tree techniques were used to determine factors affecting site productivity. However, observed site index variation explained by the regression models changes to forest sites, the minimum and maximum was found as 10,5% and 49,6% respectively. These rates for regression tree technique were minimum 30% and maximum 70%. Although changing by forest sites, the major factors affecting site productivity were latitude-longitude, elevation, temperature, precipitation, actual Evapotranspiration, soil depth and exchangeable cations (Na+, K+, Mg++, Ca++).