Investigation of the relationships between site factors and the growth of pure scotch pine stands in Ardahan region

The aim of the study was to determine the effects of some ecological factors (e.g. physiographic, climatic and edaphic) on the growth of pure scotch pine stands naturally growing in Ardahan. For this purpose 60-sample plot were selected. In each sample plot, some physiographic features (e.g. latitude-longitude, distance to the ridge, elevation, aspect and slope) and some stand characteristics (e.g. age, height and diameter at breast height) were determined. Then, the site index was calculated using stand age-top-height data. A disturbed and an undisturbed top-soil sample were taken by digging a soil pit on each plot. On each soil sample, some physical (sand, silt and clay, bulk density and soil skeleton) and chemical (pH, EC, organic matter, total nitrogen, C/N ratio) properties were determined. First, the growth of scotch pine was correlated with ecological factors by pearson correlation. Then, the site index was modeled using the ecological factors by multiple linear regression (MLR) and regression tree (RT). As a result, while the MLR model accounted for the variation in site index as between 15% and 70%, RT model accounted it as between 24% and 76%. The most important factors affecting the growth of scotch pine were slope, aspect, distance to the ridge, longitude, precipitation, annual mean temperature and clay content, respectively.