Introduction Narrow-leaved ash (NLA; Fraxinus angustifolia Vahl) and common ash (F. excelsior L.) are becoming important in European forestry due to their fast growing ability and valuable wood. Wood characteristics of NLA show similarities to common ash. It yields white, high-quality wood that is especially preferred in the veneer and furniture industries (FRAXIGEN 2005) . The mean annual increment can reach about 25 m 3 ha -1 and 15 m 3 ha -1 of stem wood over bark without any additional

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... lizers or irrigation in plantations and natural stands, respectively; current annual increments can reach 33 m 3 ha -1 of stem wood over bark at 15-20 years (Kapucu et al. 1999). NLA occurs naturally in southern Europe, the Balkans, the Caucasus, and Iran. It is the most common ash species in the northern coastal regions of Turkey and dominates the bottomland forests of the northern coastal region of Turkey where rotation age is between 40 and 50 years in plantations (Çiçek and Yılmaz 2002; FRAXIGEN 2005) . Almost all NLA-dominated bottomland forests have been converted to pure NLA plantations in the last 50 years in Turkey. However, thinning practices were not adequately implemented in the plantations. Therefore, considering that some of the NLA plantations have reached 40-50 years of age, the mean stand diameter is still low as a result of inadequate thinning practices or high stand densities. Presently, stand densities are over 350 stem ha -1 in plantations that are between 40 and 50 years old. In Europe, 60-80 future or crop trees ha -1 is suggested for common ash (F. excelsior) (Dobrowolska et al. 2011) . NLA is similar to common ash in many respects (FRAXIGEN 2005) . Therefore, a similar number of crop trees with harvesting diameters of 50-60 cm should be the target for this species. Thinning in broadleaved stands can produce large diameter trees, improve stem quality, increase merchantable volume and yield value, and shorten rotation time (