Converting monocultures into mixed stands has become a popular idea over the last decades, in light of the growing body of evidence on the positive effects of mixing tree species, on biodiversity and ecosystem functioning. On the other hand, disruption of a habitat’s temporal continuity can be detrimental for many species and affects soil conditions. We studied the effects of the reintroduction of the silver fir in beech-dominated forests on soil food web conditions and functioning. To that end, we used several indices derived from soil nematodes communities (enrichment index, structure index, nematode channel ratio, metabolic footprints) sampled in three types of stand: beech-dominated forests (N = 5), mixed silver fir–beech forests (N = 5) and pure silver fir forests (N = 5). There was no difference of soil food web conditions (structure and enrichment) between stand types. But the presence of silver fir reduced the metabolic activity and negatively affected the abundance of several trophic groups. Differences in litter quality rather than litter quantity might drive those patterns.