Data on the characteristics, removals and incomes of zone- and low-thinned stands of Norway spruce

The data collected from the experimental plots were used to describe and compare the stand characteristics and spatial patterns of Norway spruce-dominated stands after zone and low thinning at the first thinning phase, as well as the volumes harvested by these treatments. Removals of subsequent thinning and clearcutting were simulated. The thinning treatments were established in four stands dominated by Norway spruce (Picea abies (L.) H. Karst.) in Finland. Stands 1 and 2 growing on mineral soil represent young thinning stands at the stage of the first commercial thinning, whereas Stands 3 and 4 on drained peatland represent advanced thinning stands that have not been thinned previously. In younger stands, zone thinning was aimed to improve harvesting productivity, and in peatland stands, zone thinning was used as a transition to CCF. In each stand, rectangular treatment plots of 30 × 30 m (900 m2) or 20 × 30 m (600 m2), depending on the distance of strip roads, were established and all remaining trees (height > 1.3 m) were mapped and measured by species and diameter at breast height (dbh) and the heigh (dm) of sample trees was measured. The harvester production (hpr) files were used to calculate the thinning removals. The post-thinning stand characteristics were calculated using the field measurements and the KPL software of Luke. Removals of the subsequent thinning and clearcutting were predicted by using a distance-dependent, individual-tree simulator. The effects of the thinning treatments on the post-thinning stand characteristics as well as the harvested and simulated removals were evaluated by means of analyses of variance using the Univariate GLM procedure of IBM SPSS Statistics. The stand and treatment effects, as well as their interaction, were used as fixed factors. Initial differences between plots were corrected for using pre-thinning stand volume as a continuous covariate. The pairwise multiple comparisons between the treatments were performed using the Least Significant Difference (LSD) test with a significance level of 0.05.