Stand growth models for more intensive management of Juglans nigra: A case study in Croatia

Abstract

The study focuses on the development of stand growth models for more intensive management of black walnut (Juglans nigra L.) plantations in Croatia. In total, 48 plots were sampled (ages between 3 and 91 years) and, on average, 28.3 trees (between 17 and 43 trees) were measured [diameter at breast height (dbh), total height, two crown diameters, increment core] on each plot. Management scenarios with rotations of 50, 60, 70 and 80 years were developed under three different management regimes: conservative (CAS), high individual tree growth (HTGS) and high stand growth (HSGS). Indicators of competition (current annual increment in dbh, basal area and crown area) were used for scheduling thinning and the intensity of interventions for the intensive scenarios. Depending on the management options and rotation, final stand densities varied between 105 and 210 trees ha−1, mean dbh between 30.4 and 46.1 cm, and total heights between 25.9 and 29.5 m. The mean annual increment in total volume varied between 7.1 and 11.0 m3 ha−1 per year under different rotations and management options, yielding in total accumulated volume of 529–666 m3 ha−1. The CAS yielded the lowest and the HSGS the highest total volume, and HTGS yielded the highest mean dbh.