Microenvironment Impact on Survival Rate, Growth and Stability Traits, in a Half-Sib Test of Pendula and Pyramidalis Varieties of Norway Spruce

Abstract

Norway spruce (Picea abies) is a tree species with low resistance to wind storms and breakage from snow. In this study, we analyzed the microenvironmental impact on the survival rate (Sr), growth, and stability traits of 25-year-old narrow (pendula)- and normal-crowned (pyramidalis) spruce varieties in the Măneciu half-sib trial. The replication factor had a highly significant influence (p < 0.001) on the growth and stability traits and a significant influence (p < 0.05) on the Sr, which confirms the microenvironmental impact. The average Sr was 85% and was 5% higher for the pendula variety (p < 0.05). For normal-crowned trees, a negative correlation (r = −0.26***) between the crown diameter and Sr was found, while for pendula trees, the correlations were 31% lower, suggesting the pendula variety’s high adaptation potential to a denser planting scheme. The edge effect affected the Sr of both varieties almost equally, with a 3% superiority for pendula. The Sr variations in relation to the slope position indicated that the narrow-crowned variety was less affected by the slope position, while the normal variety showed significant slope variation. The pendula variety of Norway spruce could be promoted in afforestation because of its high adaptation plasticity to a denser planting scheme.