Abstract: By using traditional staining and DNA cloning and sequencing techniques, this paper studied the effects of fertilization on the arbuscular mycorrhizal (AM) colonization and AM fungal community in Elymus nutans roots across an 8-year nitrogen (N) and phosphorus (P) fertilization gradient. With the increasing level of fertilization, the AM colonization and arbuscular colonization per unit root length reduced from 67.5% to 7.3% and from 5.2% to 0.1%, respectively. A total of 24 AM fungal phylotypes were detected in E. nutans roots, whilst the mean AM fungal richness reduced from 6 to 2.6 across the fertilization gradient. Different fertilization had significant effects on the AM fungal community composition, and there existed significant correlations between the AM fungal community composition and the soil available P and root N contents. The availability of N and P increased gradually across the fertilization gradient, and had significant negative correlations with both AM colonization and AM fungal richness. It was suggested that high level fertilization would reduce the activity of AM symbionts, and result in the large loss of AM fungal biodiversity.

Key words: mycorrhizal fungi, fertilization, Elymus nutans, nitrogen, phosphorus, resource availability