Fig. 5
Soil organic carbon stock (Mg ha−1) in forest soil in the mixed plot (left) and different admixture level intervals in the plot (right). Total C stock was calculated by summarizing the predictions of each forest soil layer (forest floor and uppermost 10 cm mineral soil). Predictions were made by universal kriging and using as ancillary variables the Norway spruce litter proportion for the forest floor and the Norway spruce litter proportion and root turnover for the mineral soil. Norway spruce and European beech individual positions are marked with triangles and circles, respectively. Admixture level (0–1) was calculated from the proportion of each tree species in an area of 5 m around each sampling point. Admixture level equal to 1 corresponds to areas in which the basal area of each tree species were the same, whereas admixture level equal to 0 corresponds to those areas where only one tree species was found