Algebraic Difference Equations for Stand Height, Diameter, and Volume Depending on Stand Age and Site Factors for Estonian State Forests

Abstract

Algebraic difference equations of stand height, diameter, and volume depending on dominant species and site factors have been explored on the basis of Estonian state forest inventory data. Stand variables such as total age, average height, breast height diameter, volume, origin (naturally regenerated or cultivated), forest site type and dominant species from forest inventory database files of Estonian state forests have been used as initial data for this study. A total of 171 data series of height, diameter and volume on age were calculated as averages of data groups by site type, dominant species, origin, and age classes of 5 years. The Cieszewski, Bella (1989) algebraic difference equation has been used for model construction. First, tree parameters of the Hossfeld function were estimated for each of the height, diameter and volume series and relationships between the parameters were later studied. In the final model, dominant tree species, thickness of organic layer of soil, stand origin, height, diameter, and volume at given age were used as input variables. The model is included in the Estonian state forest information system and in several software packages for forest inventory data processing.