Effect Of Nitrogen Deposition On Soil Nematode Community Composition And Diversity In A Semiarid Grassland

Inner Mongolia steppe is located in the arid and semiarid region of North China.It is an important part of Eurasian grassland,and is very sensitive to global change.It belongs to the area which is particularly affected by nitrogen deposition.While aboveground part of grassland ecosystems has been widely studied,how soil biotic communities responding to nitrogen deposition is still unclear.Therefore,in this study,the effects of nitrogen deposition on the community composition and diversity of soil nematodes in different seasons were studied based on the long-term nitrogen deposition simulation test platform of National Field Science Observation and Research Station of Grassland Ecosystem in Xilingol,Inner Mongolia.The relationship between diversity and stability of soil nematode communities,and the correlation between aboveground plant diversity and soil nematode diversity were revealed under simulated nitrogen deposition.The interactive effect of nitrogen deposition and mowing on soil nematode communities was elucidated in the present study.The results showed that:(1)Total nematode abundance and the four trophic groups were significantly decreased with increasing nitrogen addition rates across different sampling seasons.Higher nematode basic index(BI)and lower structure index(SI)were observed in the highest nitrogen addition rate in the present study,which indicated that the soil food webs were simplified and disturbed.(2)Positive correlations were found between stability and diversity,richness of soil nematode community under nitrogen addition.Nitrogen addition indirectly altered the temporal stability of nematode community by reducing the richness and abundance of soil nematodes.(3)Positive correlations were found between aboveground plant diversity and soil nematode diversity in the present study,and showed a close linkage between aboveground and belowground biodiversity in the grassland ecosystem.Therefore,simulated nitrogen deposition negatively affected the aboveground-belowground biodiversity in the present study.(4)The interactive effects of nitrogen addition and mowing on total nematode abundance were observed in this study.Nitrogen addition influenced soil nematode communities by changing soil p H and soil moisture.However,mowing could not mitigate the negative effects of nitrogen addition on soil microfood webs.In summary,nitrogen deposition can adversely affect soil nematode community composition and diversity indirectly in the semiarid grassland.However,mowing could not alleviate the negative effect of nitrogen deposition on belowground organisms.The results of this study could provide a scientific basis for further understanding the influence mechanism of environmental changes caused by nitrogen deposition on belowground ecological processes.