Vertical distribution of soil carbon in boreal forest under European beech and Norway spruce

Past forest management decisions have resulted in European beech being replaced with Norway spruce across Europe. Previous studies have revealed variances in soil carbon (C) under different dominating tree species. Yet, there is a scarcity of knowledge about how beech and spruce differ in impact on forest soil C in boreal regions, where beech has its northern distribution limit. We have therefore compared soil C in a natural beech forest (Be) with that of two spruce forests: one planted on former beech forest (SpBe) and the other on former spruce forest (Sp), in South-East Norway. Analyses of biochemical parameters and fungal biomass were performed along fine-scaled soil profiles, covering both the organic and mineral layers. We found no significant difference between the forests when comparing estimates of total C stocks per area. However, throughout the soil profile, the distribution of soil C in Be varied significantly from SpBe, while Sp was intermediate. The distribution of fungal biomass along the soil profile in Be varied significantly from the two other forests. Hence, fungal biomass may drive the observed differences. Soil C, nitrogen (N), and C/N ratios were forest type and soil depth dependent, whereas forest type had an effect on the vertical distribution of condensed tannins and fungal biomass. Our results suggest that the presence of beech or spruce as the dominant tree species in the studied area has an effect on the vertical distribution of soil properties, while there is no major difference when comparing the whole soil profile.