Soil microbial networks mediate long-term effects of nitrogen fertilization on ecosystem multiservices

Nitrogen (N) fertilization is known to impact the capacity of ecosystems to support multiple ecosystem services such as carbon sequestration and nutrient cycling, particularly in nutrient-limited environments. Yet, little is known about how N fertilization may result in trade-offs across contrasting soil ecosystem services. Moreover, the contribution of soil microbial networks as mediators of the impacts of fertilization on soil ecosystem services is poorly understood. Here we collected topsoil (0–10 cm) and subsoil (10–20 cm) samples from a 13-year N addition experiment in a semiarid grassland to investigate how long-term N additions affect soil multiservices. We found that soil multiservice predominantly exhibited a hump-shaped response to the increasing levels of N addition across two soil depths. More importantly, changes in the complexity of soil microbial networks were positively correlated with ecosystem multiservices across the two soil depths. This relationship was especially important in explaining topsoil multiservice responses, while in subsoils, multiservices were more strongly associated with abiotic properties than network complexity. This distinction may be attributed to the lower microbial activity and reduced nutrient utilization capacity in subsoils, which allows abiotic factors to play a more dominant role on multiservices. Synthesis. Our results highlight that soil microbial network complexity is highly correlated with multiple ecosystem services in the context of global atmospheric N deposition.