engleski

Training shapes and forms in broadleaved clonal seed orchards

In accordance with the delineation of Regions of Provenances of forests in Croatia into ecogeographic seed regions and zones, the following clonal seed orchards have been established: three orchards of pedunculate oak (Quercus robur L.), two of narrow-leaved ash (Fraxinus angustifolia Vahl), one of sessile oak (Quercus petraea (Matt.) Liebl, ) and one of wild cherry (Prunus avium L.). Phenotypical selection and heterovegetative propagation of plus trees, as well as the establishment of clonal seed orchards were aimed at obtaining regular yield periodicity and forest seed of good genetic quality in the categories Qualified and Tested. Different pomotechnical treatments (training systems) were applied to each tree species ; For pedunculate and sessile oak oval spindle training system, for narrow-leaved ash spindle pyramid and for wild cherry spindle bush training system. Training systems should provide a strong framework and good light penetration in the canopy. The forming pruning is used to bring the grafts into the required training shape whereas pruning for higher yield maintains the adequate balance between the growth and the seed production. Tree pruning and training started right after the planting with a goal to gain desired canopy shape with well-deployed scaffold branches in the next 7 or 8 years. The main function of pruning is the removal of competing shoots to enforce the growth of remaining desired ones. Pruning intensity, i.e. the relation between vegetative and generative buds in the canopy determines the tree’s condition, density and yield. The balance between vegetative and generative buds can only be achieved by appropriate underground and aboveground tree parts pruning. The evaluation of genetic values of mother trees in progeny tests and genotypic selection were also started to obtain increased genetic gain.

Quercus robur; Quercus petraea; Fraxinus angustifolia; Prunus avium; pomotechnical treatments; clonal seed orchards

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