Investigation of some ecological conditions affecting the productivity of eastern spruce forests in Ardanuç district

The study has investigated the effect of some ecological conditions (soil, climate, and location) on the productivity of pure and mixed stands of oriental spruce (Picea orientalis (L.) Link) in the Ardanuç district. In this context, 53 sample sites were selected from pure and mixed spruce stands within the borders of Ardanuç district. In each sample plot, some site and stand characteristics were measured. Then, the site index (SI) showing the productivity of stands was calculated using age and top height for each sample plot. A disturbed and undisturbed soil sample was taken from subsoil and topsoil digging a soil pit in each sample plot. Physical (sand, clay, and silt contents, bulk density, and skeleton) and chemical (pH, electrical conductivity, and organic carbon) properties of soils were analyzed on each sample. Pearson correlation between the SI of spruce stands and site factors was performed first. Then, multilinear regression (MLR) and regression tree (RT) models were developed to predict SI. MLR and RT accounted for 49-60% and 36-55% of the variation in SI, respectively. The most important environmental factors affecting the SI in Ardanuç forests were precipitation, aspect, soil bulk density, longitude (X), and soil skeleton content.