Nitrogen(N)deposition,the source of N input into terrestrial ecosystems,is exhibiting an increasingly serious impact on the biogeochemical cycle and functional stability of ecosystems.Grasslands are an important component of terrestrial ecosystems and play a key role in maintaining terrestrial ecosystem balance.Therefore,it is critical to understand the effects of nitrogen addition on grassland ecosystems.We conducted gradient N addition experiments(0,3,6,and 9 g N m-2 y1)for three years in grassland communities with similar site conditions.We utilized four typical herbaceous plants,including the dominant species Bothriochloa ischemum(B.ischemum)and companion species Stipa bungeana(S.bungeana),Artemisia gmelinii(A.gmelinii),and Cleistogenes squarrosa(C.squarrosa),to explore how different plant-soil-microbe systems respond to N addition.Stoichiometric homeostasis analysis demonstrated that both plants and microbes were strictly homeostatic.However,the companion species were found to be more susceptible to P dominant species.Furthermore,aggravated overlap in stoichiometric niches between plant species were observed at the N6 and N9 levels.Vector analysis indicated that the vector angle was＞45° regardless of plant species and N levels,suggesting that there was a strong P limitation in the rhizosphere microbial community.Variation partitioning analysis revealed that the Composite roots exhibited a greater effect(explaining 34.7％of the variation)on the rhizosphere microbes than on the Gramineae,indicating that there may be more intense nutrient competition in its rhizosphere.In general,the effects of N addition on species were different across functional groups,with a significant positive effect on the Gramineae(B.ischemum,S.bungeana,and C.squarrosa)and a significant negative effect on the Compositae(A.gmelinii),which should be fully considered in the future ecological management and restoration.

State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau,Institute of Soil and Water Conservation,Northwest A&F University,Yangling 712100,China;Key Laboratory of National Forestry and Grassland Administration on Ecological Hydrology and Disaster Prevention in Arid Regions,Xi'an University of Technology,Xi'an 710048,China;Institute of Soil and Water Conservation,Chinese Academy of Sciences and Ministry of Water Resources,Yangling 712100,China

[1]ZiWen Zhao;YanLi Qin;Yang Wu;WenJing Chen;Sha Xue;GuoBin Liu-.Effects of nitrogen addition on plant-soil-microbe stoichio-metry characteristics of different functional group species in Bothriochloa ischemum community)[J].土壤生态学快报（英文）,2022(04):362-375

stoichio,ischemum,Grasslands

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