| Arbuscular mycorrhiza (AM) fungi spread widely in the terrestrial ecosystem. AM fungi can promote plant capability in nutrient uptake, maintainance of plant diversity, increase soil organic carbon, improve soil structure as well as enhance ecosystem stability. The ecological function is tightly correlated with diversity and community composition of AM fungi. The dramatic climate variation in mountain system, and the biotic turnover over short spatial scales provide an excellent opportunity to examine the distribution pattern of AM fungi. The Tibetan Plateau is the highest and largest plateau in the world. The uique geographical location of Tibetan Plateau is sensitive to global change. Soil carbon accounts for over2.5%of world carbon content. The contribution of AM fungi to soil carbon sequestration is of significant importance in predicting the influence of climate change on biotic response. The present study was conducted on Mount Segrila and Mount Mila. The influences of land use types (forest, grassland and farmland) on AM fungi were also considered. Cloning sequencing and454sequencing were performed to explore the distribution patterns of AM fungi and the potential driving force. The relationship among AM fungi, soil aggregates and soil carbon was also investigated. The main results are as followed:(1) A total of95OTUs belonging to7families of AM fungi were detected from roots of Pennisetum centrasiaticum var. centrasiaticum, Carex pseudofoetida Kuk and Fragaria moupinensis along an altitudinal gradient (3105m-4556m) on Mount Segrila, and32OTUs were novel. Results of2011showed no significant influence of plant species and elevation on roots colonization, hyphal length density and spore density. By contrast, the results of2013were different from those of2011. Two-year results consistently showed that overall no significant difference was observed among AM fungal communities between different plants. However, the AM fungal community of the two co-occurring plantspecies differed significantly at3105m in2011, while the fungal communities differed significantly among three plants at all elevations in2013.(2) The OTU richness and phylogenetic diversity of AM fungi at4556m were significantly higher than those at3570m, AM fungal communities differed significantly between the two elevations. Elevation mainly influenced AM fungal diversity and community composition by indirect path mediated by soil pH and available P. OTU richness at low elevation was negatively correlated with plant species richness, while OUT richness was positively correlated with plant richness at high elevation. Plant biomass was positively correlated with net relatedness index of AM fungi at each elevation.(3) Plants of Kobresia pygmaea and C. pseudofoetida were the two dominant sedge species on Mount Mila. The two plants harboured similar AM fungal communities (except at4150E). No significant difference in AM fungal diversity was found between the two plant species irrespective of elevations. The relative abundance of K. pygmaea and C. pseudofoetida contributed largely to soil macroaggregates. AM fungi contributed to macroaggregates mainly through indirect path mediated by hyphal length density. There was a strong positive correlation between glomalin related soil protein (GRSP) and soil carbon and N.(4) AM fungal diversity in farmland was significantly higher than that in forest and grasslands. AM fungal community composition differed significantly among the three land use types. Glomeraceae, Gigasporaceae and Acaulosporaceae were the most dominant AM fungal families, and their relative abundance differed significantly across different land use types. Land use change affected AM fungal community and hyphal length density through indirect path mediated by soil pH. Both hyphal length density and GRSP were positively correlated with soil total C and N. Land use type mainly influenced macroaggreates and total C through indirect path mediated by hyphal length density and easily extractable GRSP. |
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