Leaf unfolding variability in clonal seed orchard of Fraxinus angustifolia Vahl

In Croatia, narrow-leaved ash (Fraxinus angustifolia Vahl) is distributed in the Pannonian lowland area, along the rivers with pedunculate oak (Quercus robur) in mixed stands. Greatest portion of its genetic variability is localized in the region of Sava river (area of 30 000 ha) where was in 2005 established clonal seed orchard with 56 clones (Forest Range Office Nova Gradiška). The grafts were planted with 4 × 4 m spacing in the area of 3.50 ha. Clonal seed orchard have been regularly maintained by pruning and with other agrotechnical treatments from the moment of establishment. Pomotechnical treatments are used and successful pomology techniques is maintaining the balance between the vegetative and generative activity. Phenological seasonal rhythm has recently receives importance and with better understanding of leaf phenophases we will be able to more precisely define response to climate change.