Neutral effect of nitrogen addition and negative effect of precipitation reduction on the soil faunal community in a temperate forest

Abstract

ABSTRACT Nitrogen deposition can promote belowground soil carbon pools, and precipitation reduction can eliminate this positive effect. Soil fauna play crucial roles in regulating the dynamics of organic matter and maintaining biodiversity in ecosystems. However, it is not clear whether belowground soil fauna have similar responses to changes after long-term nitrogen deposition and drought. We simulated nitrogen deposition by applying fertilizer, and simulated drought by excluding 30% of the ambient precipitation in a temperate forest from 2009. Our results showed that experimental precipitation reduction alone significantly changed the composition and decreased the abundance of the soil faunal community. Precipitation reduction could also promote the soil food web in a fungal-dominated pathway by decreasing trophic groups of Isotomidae abundance. In contrast, although nitrogen addition treatment increased soil available nitrogen content, it had a neutral effect on the soil faunal community. Soil faunal community showed strong temporal variations in response to both nitrogen deposition and precipitation reduction treatments. Notably, interactions between precipitation reduction, nitrogen addition, and sampling time were significant for specific trophic groups, including saprozoites and omnivores. Shannon-Weiner diversity was not sensitive to these global change factors. Our results suggest that soil water content and plant richness may, directly and indirectly, regulate the soil faunal community.