Afforestation with non-native tree species represents a common global strategy for restoring degraded ecosystems. While the impacts of non-native forest plantations (NNFPs) on plant diversity are well-documented, the effects on soil biota and the associated ecosystem functions remain less understood. Here, we examined the soil biota and indicators of soil functions, including soil microbial activity and invertebrate decomposer feeding activity, in areas where Robinia pseudoacacia (black locust; BL) had been planted 17, 20, and 32 years ago, as well as in adjacent grassland in the Loess Plateau. We observed that the diversity of microbes and invertebrates was not affected by the presence of BL plantation or its age. The community composition of bacteria and eukaryotes was significantly affected by the plantation age. In contrast, that of mites and springtails did not vary with plantation age. Moreover, BL plantation did not affect invertebrate decomposer feeding activity, with the mean bait consumption proportion being 14.8 %, 12.2 %, 14.7 %, and 13.4 % in 32-Y, 20-Y, 17-Y, and grassland plots, respectively. However, soil microbial activity increased with plantation age and was higher in 32-Y plots (+170 %) compared to grassland plots, which was primarily attributed to changes in soil total nitrogen and the microbial community. Overall, these results demonstrated that BL plantation had differential effects on the communities of soil microbes and invertebrates as well as their activities. These findings highlight the importance of considering multiple soil biota groups when evaluating the ecological consequences of non-native tree afforestation.