Stand development in uneven-aged sub-alpine Picea abies stands after partial harvest estimated from repeated surveys

Abstract

Eight sub-alpine stands in mid-Sweden, dominated by Picea abies (L.) Karst., and subjected to commercial partial harvests in 1972-1973, were inventoried with circular plot surveys in 1973 and 1993. All trees with d.b.h. (diameter at breast height) > 2 cm were included in the analysis. All stands had d.b.h. distributions where number of trees declined over d.b.h. in both 1973 and 1993. The height-diameter relationship had become more linear and less steep in the lower d.b.h. classes during the 20 years. Standing volumes after the 1973 harvests, were 9-37 m3 ha-1. Mean annual volume increments during the 20 years were 0.4-1.4 m3 ha-1 a -1. Using the 1993 height curve to estimate standing volume in 1973 caused a systematic overestimation of volume increment of 0.1-0.4 m3 ha-1 a-1 for the eight stands, i.e. on average an overestimation of ∼27 per cent. Ingrowth of Norway spruce past 8 cm d.b.h. was on average ∼10 stems ha-1 a-1, and not significantly correlated with either the number of spruce stems 4-8 cm d.b.h., or the standing volume in 1973. The relationship between results from different kinds of studies (repeated surveys, reconstructions, permanent plots) was discussed. The study showed that heavy harvests, creating stands with standing volumes below 50 m3 ha-1, result in low levels of current annual volume increment, and do not positively affect ingrowth.