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Distribution and Management of Black Walnut (Juglans nigra L.) in Croatia

Black walnut (Juglans nigra L.) was introduced in forest management around 1890 in the lowland regions of eastern Croatia to establish plantations on the sites too dry for the most valuable native species, pedunculate oak (Quercus robur L.). Aim of the article was to perform a preliminary research of the distribution and representation of black walnut in Croatian lowland forests, and of their significance in the management of lowland forests. A database of plantations was established from the management plans (age, area, standing volume of black walnut, total standing volume, coordinates). Gauss-Krüger coordinates were used for mapping the distribution of black walnut (ArcView 3.3 software, UTM grid). Fifty subcompartments were randomly selected for ground surveying (assessment of stand structure, collecting of samples of fertile twigs with leaves and fruit). A total number of 416 subcompartments (3, 162 ha) with black walnut as pure stands (143 subcompartments, 827 ha) and with black walnut as partial stands, groups of trees, or individual trees was established. The total standing volume of black walnut was estimated to be 239, 678 m3 (in pure plantations 112, 198 m3). No hybrid between black walnut and Persian walnut was found. The age structure of plantations was disrupted during the war in Croatia when the most valuable plantations of around 80 year old trees were felled on the occupied territory. Black walnut became a valuable exotic species in forest management on the sites too dry for the most valuable indigenous species, pedunculate oak, in eastern Croatia.

Black walnut; Croatia; management; distribution

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