Growth response of spruce stands to subsiding air pollution load at promoted development of crowns

Development of artificial spruce stands grown under air pollution load in different stand tending regimes was studied in the Moravian-Silesian Beskids in Spruce-Beech altitudinal vegetation zones (980--1075m a.s.l.) with the aim to check in the mountain forest the efficiency of a so-called crown management focused on the creation of large crowns with abundant assimilatory apparatus. The authors worked with a false time series of values from three cases of stand comparison. The stands were aged 1) 18 years, 2) 41 and 46 years and 3) 52 and 62 years. Changes of stand density, stand basal area, diameter structure and slenderness ratio were recorded for 23 or 19 years. It was demonstrated that the release of crowns had the greatest effect in young stands; even if carried out at the age of about 40 years of the stand, its effect still cannot be considered negligible. Through stimulating the diameter increment, the mean stem diameter increases along with the proportion of large-diameter trees and with the improving slenderness ratio. The stands responded to the decreased air pollution load by the increased diameter growth.