Growth and Increment of Black Walnut (Juglans nigra L.) in Eastern Region of Croatia

This paper deals with growth and increment dynamics of black walnut trees in culture planted at the Vukovar area in eastern region of Croatia where black walnut has been cultivated for more than one century. Culture is situated inside the zone of most xerotherm subassociation of common oak and hornbeam forest (Carpino betuli - Quercetum roboris quercetosum cerris Raus 1989). The results of analyzing representative trees (from young, middle aged and adult stand) show that black walnut is fast growing tree species with height increment culmination before age of twenty years. Black walnut trees at the age of fifty years achieve height of thirty meters and breast height diameter of thirty centimetres, on the site of first productivity class. Volume increment of black walnut trees is continuous evert in the age of sixty to eighty years. Comparing black walnut volume growth until the age of sixty years with growth of other tree species on the high quality site, it was determined that black walnut growth is faster and better then common oak (Quercus robur L.), narrow-leaved ash (Fraxinus angustifloa Vahl), black alder (Alnus glutinosa (L.) Gaertn.), and introduced green ash (F. pennsylvanica Marshall). According to determined growth and increment dynamics, introduction of black walnut in the appropriate habitat was proved justified. Even higher productivity of black walnut cultures could be achieved by paying more attention to plantation cultivation, especially timely thinning.