Long-term nitrogen addition and precipitation reduction decrease soil nematode community diversity in a temperate forest

Abstract

Terrestrial ecosystems are driven by different global change factors, such as atmospheric nitrogen deposition and precipitation reduction. Nitrogen deposition and precipitation reduction have a great impact on the above- and underground processes. Most previous studies mainly focused on the effects of nitrogen deposition and/or precipitation reduction on aboveground processes, while the effects on underground processes were relatively scarce. As an important part of the underground soil food web, soil nematode community occupies different nutritional niches and is sensitive to external disturbances, and it is often used as indicator for studying underground processes. However, we know little about the response of soil nematode community to nitrogen deposition and/or precipitation reduction. Here, we used a 10-year of factorial manipulation by applying nitrogen solution and reducing the amount of precipitation to the soil, and to investigate the responses of soil nematode community to nitrogen deposition and/or precipitation reduction in a temperate forest. We expected that nitrogen addition could promote while precipitation inhibited the activity of soil nematode community. Furthermore, we expected nitrogen addition and precipitation could have interactive effect on soil nematode community. Our results found that nitrogen addition and/or precipitation reduction treatment caused significant changes in the composition of soil nematode community. Nitrogen addition and nitrogen addition combined with precipitation reduction induced negative effects and significantly decreased the abundance and diversity of soil nematode community, while precipitation reduction only decreased the abundance of soil nematode community. Nitrogen addition and precipitation reduction had synergistic effect on soil nematode community with higher trophic levels. Compared with precipitation reduction treatment, the negative effect of nitrogen addition on soil nematode community was more severe. According to the structural equation model (SEM), we found that nitrogen addition and precipitation reduction could affect the abundance of soil nematode community by affecting the plant richness and soil pH. Since the decrease of enrichment index (EI) and the increase of structure index (SI), our research results revealed that nitrogen addition could lead to soil food web in a lower nutrients available condition.