title: Differential responses of arbuscular mycorrhizal fungi to nitrogen addition in a near pristine Tibetan alpine meadow.
abstract: Elucidating the responses of soil microbial abundance and community composition to nitrogen (N) addition is important for predicting ecosystem function under increased atmospheric N deposition. We examined the arbuscular mycorrhizal (AM) fungal community under three N forms (NH4(+)-N, NO3(-)-N, and NH4NO3-N) and two N rates (1.5 and 7.5 g N m(-2) year(-1)) in an alpine meadow of the Qinghai-Tibetan Plateau. AM fungal extraradical hyphal density was significantly decreased by NH4(+)-N in May, but was not affected by N form nor N rate in August. N rate, but not N form, significantly affected AM fungal spore density; high N rate decreased spore density. No direct N addition effect was observed on AM fungal community; however, soil available phosphorus, pH, and NO3(-)-N were considered as important factors that influenced AM fungal community composition. Structural equation model results showed that N rate, not N form, strongly affected soil characteristics, which directly influenced community compositions of plants and AM fungi, as well as spore density. Therefore, AM fungal community was influenced by N addition, primarily because of altered soil characteristics, and partially by a modified plant community, but not or just slightly by direct N addition effects in this alpine meadow ecosystem.
authors.affiliation: State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Zheng
authors.forename: Yong-Chan
authors.initials: YC
authors.lastname: Kim
authors.forename: Xiao-Fang
authors.initials: XF
authors.lastname: Tian
authors.forename: Liang
authors.initials: L
authors.lastname: Chen
authors.forename: Wei
authors.initials: W
authors.lastname: Yang
authors.forename: Cheng
authors.initials: C
authors.lastname: Gao
authors.forename: Ming-Hua
authors.initials: MH
authors.lastname: Song
authors.forename: Xing-Liang
authors.initials: XL
authors.lastname: Xu
authors.forename: Liang-Dong
authors.initials: LD
authors.lastname: Guo
mesh_terms: D005658:Fungi / Q000145:classification* / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism; D065948:Grassland; D025301:Hyphae / Q000254:growth & development; D038821:Mycorrhizae / Q000145:classification* / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D012988:Soil Microbiology; D013172:Spores, Fungal / Q000254:growth & development; D018609:Tibet
chemical_list: D009584:Nitrogen
keywords: 454 pyrosequencing; AMF; Qinghai-Tibetan Plateau; community composition; nitrogen deposition