Growth and yield for scots pine and oriental beech mixed stands in different mixture ratios

Mixed forest ecosystems are important to human life. In general, there are many positive aspects of mixed stands compared to pure stands biologically and ecologically. In forestry, the importance of mixed stands has increased in recent decades due to the potential benefits which can be gained, such as increased production, greater diversity, improved nutrient cycling or reduced risk of biotic and abiotic damage. Scots pine (Pinus sylvestris L.) and Oriental beech (Fagus orientalis Lipsky) are two of the most important tree species in Turkey. Mixed Oriental beech and Scots pine stands with different forest structures and biodiversity are widespread in Black Sea Region, Turkey. The management of mixed stands of these species is of increasing importance to foresters in Turkey, and a crucial factor is knowledge of the growth and yield relationship for the sound management of these stands. This study aimed to determination of the growth and yield relationship for Scots pine and Oriental beech mixed stands in different mixture ratios in Black Sea Region. The data were obtained from 162 temporary sample plots with ranging stand ages, site index, density and mixture percentages. The diameter at breast height of all trees, height and age of a sufficient number of trees for each sample plots were measured and the average age, site index, density and mixture percentage were estimated by these data. The sample plots have 31-150 years for Scots pine and 33-117 years for Oriental beech of stand age range, 16.2-34.9 m Scots pine and 14.7-32.3 m for Oriental beech of site index range, 0.10-0.76 of Scots pine mixture ratio range, 2.9-10.0 of stand density range. With the generated equation systems, stand age, site index, density and mixture ratio of the four such as age, site index, density and mixture percentage main factors in Oriental beech - Scots pine mixed stands, including the effects on the stands were determined numerically. Volume of main stand and mean annual volume growth show irregular depending on the mixture ratio for the same average age, site index, density and mixture percentage. The number of Oriental beech trees are increasing, while number of Scots pine trees and total number of trees are decreasing depending on the mixture ratio for the same average age, site index, density and mixture percentage. Average height for both species is increasing when mixture ratio is increased to 0.4 to 0.8 for the same average age, site index, density and mixture percen