Community variation characteristics and driving pathways of soil microarthropods in meadow steppe under different nitrogen application durations

Soil microarthropods are important links between aboveground and belowground food webs in grassland ecosystems and are sensitive to changes in environmental conditions. However, the continuous changes in soil microarthropod community characteristics under the threat of increasing global nitrogen (N) deposition remain unclear. On the basis of the N deposition simulation experiment design in 2010 for the Stipa baicalensis meadow steppe, 8 N treatments (0 (control group), 15, 30, 50, 100, 150, 200, and 300 kg ha⁻¹ yr⁻¹) were used to analyse the changes in the soil microarthropod community structure and diversity characteristics and their potential driving pathways after 10, 11, 13 and 15 years of N addition. Microdispidae of Prostigmata (prostigmatid mites) consistently appeared as a dominant taxon across multiple years (the 10th, 11th, 13th, and 15th years of N application). With increaseing N application rates and duration, the abundance and taxa of Prostigmata gradually, increased, whereas the abundance and taxa of Poduromorpha (poduromorph springtails) and Entomobryidae (entomobryid springtails) decreased. Therefore, Prostigmata gradually dominated the composition of soil microarthropod community. There were significant differences in the soil microarthropod community structure among the different N rates and durations of application. However, with increasing N application rates and durations, the Jaccard index gradually increased, and the difference in the soil microarthropod community structure gradually decreased. Long-term N addition had a threshold effect on the abundance and diversity of soil microarthropods, with a threshold of 200 kg ha⁻¹ yr⁻¹. Precipitation and pH values were the main factors driving the characteristics of changes in the soil microarthropod community in the meadow steppe under different years of N application. In summary, long-term N application significantly changed the soil microarthropod community in the S. baicalensis meadow steppe, and the interannual changes in the soil microarthropod community were regulated by both climatic and environmental factors under N application.