Stem and Crown Characteristics of Norway Spruce [Picea abies (L.) Karst] Populations from Romanian Carpathians

Abstract

To establish the most important Norway spruce Romanian populations, open-pollinated progeny of ten plus trees originating from 33 seed stands mapped in the Romanian Carpathians have been evaluated for stem and crown characteristics at the age of 30 years, in two field trials: one established in their natural range (Brețcu trial), while the second was located outside of their natural range, in Subcarpathian lands (Avrig trial). Significant (p < 0.05) differences were found among the seed stands in both sites for most of the characteristics, suggesting an additive genetic control with different levels of significance depending on the evaluated trait and the testing site. Location analysis also revealed a highly significant population x locality interaction for all traits. The same populations behave differently to the change of the ecological conditions. In the Avrig trial higher values were recorded than in the Brețcu trial for the tree slenderness coefficient (19%), crown slenderness coefficient (13.6%) and crown lateral area (9.4%). Although outside of their natural area, pruning height (m) increased 6.4%, however pruning height ratio (%) decreases by 1%, compared to the test established in their natural range. The populations from the Eastern Carpathians stand out by showing sustained growth and superior wood quality, while the populations from the Western Romanian Carpathians have generally smaller differences between the mean values of analysed traits in both field trials. Qualitative characteristics that influence the stability of stands to windthrow and snowbreak showed low levels of correlations to ecological gradients of the originating location of tested seed stands.