Bitternut hickory (Carya cordiformis(Wangenh) K. Koch), a successful non-native tree species in the north-west of Romania

The most abundant and most uniformly distributed of all the hickories (<i>Carya</i> spp.), growing throughout the eastern United States, bitternut hickory was introduced to Europe after 1689. It was used as ornamental species especially in parks and dendrological gardens as well as forest species in some European countries (e.g. Austria, Belgium, France, Germany).<br /> In Romania, it was planted exclusively in parks and dendrological gardens, with the exception of Sacueni Forest District. In this area, the first three individuals of bitternut hickory were planted in 1900, reaching nowadays breast diameters between 72.3 cm and 79.2 cm and heights over 25 m. Using seeds collected from these trees and seedlings produced in the local nursery, the species has expanded after 1957 and the total area of thirteen stands including bitternut hickory reaches nowadays 39.21 ha, with some interesting characteristics:<br /> - it is found in monocultures as well as mixed stands (proportion between 10 percent and 90 percent) with different broadleaved tree species, both native (pedunculate oak <i>Quercus robur</i> L., small-leaved linden <i>Tilia cordata</i> L., sycamore <i>Acer pseudoplatanus</i> L.) and exotic (black walnut <i>Juglans nigra</i> L., northern red oak <i>Quercus rubra</i> L., pin oak <i>Quercus palustris</i> Muenchh., and black cherry <i>Prunus serotina</i> Ehrh.);<br /> - bitternut hickory grew quickly in youth and reached mean diameters between 18 cm (25-30 years of age) and 32 cm (60 years) and mean heights between 16 m (25-30 years of age) and 25 m (60 years). These dimensions are similar to or even bigger than the associated species, both native and exotic;<br /> - the species regenerates easily by seed and its seedlings have a higher shade tolerance than most of its associates, even though bitternut hickory is considered as intolerant of shade;<br /> - it is a good self-pruner and epicormic branching is not a problem;<br /> - it has never been affected by any damaging agent and is wind-firm, owing to its dense root system, with a pronounced taproot. Keywords: Sustainable forest management, Adaptive and integrated management ID: 3471954