Tree biomass allometry during the early growth of Norway spruce (Picea abies (L.) Karst) varies between pure stands and mixtures with European beech (Fagus sylvatica L.)

In this paper we report an investigation of how forest stand mixture may affect biomass allometric relationships in Norway spruce (Picea abies (L.) Karst). Analysis of aboveground biomass data was conducted for 50 trees. Twenty-five sample trees were from a pure Norway spruce stand and the remainder were taken from a mixed stand of Norway spruce with European beech (Fagus sylvatica L.). ANCOVA results demonstrated that individual tree biomass allometry of the pure stand significantly differed from that of the mixed stand. Allometric characteristics depended on the biomass component recorded and the type of biomass predictor used. When predicted by DBH and/or height, the total aboveground biomass of mixed stand trees was significantly less than that for pure stand ones. This ‘apparent’ lower aboveground biomass was attributed to the lower branch and needle biomass proportions of trees growing in mixed stands. The findings indicate that caution should be exercised when applying biomass allometric models developed from pure stands to predict tree biomass in mixed stands (and vice versa), as such data treatment may introduce significant bias