Black walnut (Juglans nigra L.) standing volume in the riparian forests of the Czech Republic

Black walnut (Juglans nigra L.) is one of the most valuable non-native tree species growing on alluvial soils in the southeastern part of the Czech Republic. However, its standing volume is currently calculated according to oak tables, although its growth and standing volume is likely different. In order to determine the observed black walnut standing volume and to express a difference between black walnut and other main tree species growing on alluvial soils, 63 temporary sample plots of pure black walnut stands were established and, for determination of tree volume, 63 sample trees with various dimensions were felled and measured in sections. Mensurational data were evaluated using a Korf growth function, which is one of best growth functions for expressing the development of standing volume. Moreover, a reciprocal Korf function was used for fitting the decline in the number of trees. For determination of standing volumes, 2 methods using Korf functions were used and their results were compared. The black walnut standing volume of 100 years is 706 m³ ha^-1 if we use the fitted mean diameter and height for calculation and 724 m³ ha^-1 if we use the Korf function for fitting the observed standing volumes in the sample plots. Both results are higher than the oak standing volume growing on the best site by 100 m³ ha^-1 and higher than the ash standing volume by approximately 200 m³ ha^-1.