The aim of this study was to determine how soil chemistry and the distribut
ion of fine roots (<1 mm) in the organic and upper mineral soil horizons we
re affected by an admixture of birch (Betula pendula Roth and B. pubescens
Ehrh.) in Norway spruce (Picea abies (L.) Karst) stands. The surface organi
c horizons (LF and H) and mineral soil were characterized to a depth of 10
cm on three sites in southern and central Sweden. On these sites, replicate
d plots had been established that contained either ca. 30-year-old birch gr
owing as a shelter over similar-aged spruce (mixed plots) or spruce only. T
he treatments had been created 8-11 years before this study was done. A fou
rth site, with plots containing ca. 90-year-old spruce or birch/spruce, and
a fifth site, with 30-year-old spruce and a low admixture (12% by basal ar
ea) of birch, were also included in the study. Concentrations of Ca and Mg
and pH in the LF layer were significantly higher in plots with a birch admi
xture. In the H-horizon, concentrations of K, Ca and Mg were significantly
higher in mixed plots than in plots with pure spruce. Consequently, base sa
turation was higher in mixed plots than in pure spruce plots. A shelter of
birch decreased the total amount of spruce fine roots (<1 mm), as revealed
at one of the sites. Total fine root biomass (birch + spruce) in the organi
c and mineral soil horizons (to 10 cm) did not differ significantly between
the pure spruce stands and the spruce stands with a birch shelter. (C) 200
0 Elsevier Science B.V. All rights reserved.