Site index conversion equations for Picea abies and five broadleaved species in Sweden: Alnus glutinosa, Alnus incana, Betula pendula, Betula pubescens and Populus tremula

In the study 104 stands of Norway spruce [Picea abies (L.) Karst.], silver birch ( Betula pendula Roth), downy birch (Betula pubescens Ehrh.), common alder [Alnus glutinosa (L.) Gaertner], grey alder (Alnus incana Moench) and European aspen (Populus tremula L.) were used for developing site index conversion equations by analysing stands where two or more species were growing close to each other. The stands were located at latitude 56 - 63 degrees N in Sweden. In most localities paired comparisons were made between Norway spruce and one of the broadleaved species, but in some cases paired comparisons were made with two of the broadleaved species. In all, 46, 39, 37, 21 and 20 pairings of Norway spruce with European aspen, silver birch, downy birch, common alder and grey alder, respectively, were measured and analysed in the study. Coefficients of determination for predicted equations varied between 0.31 and 0.51 for pairs of Norway spruce and the broadleaved species. The presented site index conversion equations could be used as tools for choosing appropriate species for a site. The information provided by the site indicator(s) should be used as one factor when making final management decisions regarding future forest stands for the production of wood products or for maintaining desired levels of biodiversity.