| Arbuscular mycorrhiza(AM)fungi are very important soil microorganism that can form symbiotic symbioses with the roots of most terrestrial plants.It plays an important role in promoting plant nutrient absorption,enhancing plant stress resistance,influencing and regulating the ecology.The AM fungi are very sensitive to the changes of the ecological environment,and their species and functional diversity are important influencing factors to maintain the stability of the ecosystem.Although the ecological significance of arbuscular mycorrhizal fungi has been widely recognized,little is known about the biological diversity,species distribution pattern,and influencing factors of AM fungi.This has seriously hindered the further development of AM fungi.In this study,we took the Qinghai-Tibet Plateau as the study area,this paper collected 600 samples of 120 sites in three main vegetation types(alpine desert steppe,alpine meadow,and alpine steppe)in the area of about 880,000 km2,systematically studied the spatial distribution pattern of the AM fungal community and its influencing factors,the main results obtained are as follows:(1)AM fungus was ubiquitous in the study region:the root length colonization of AM fungi was between 5.4%and 87.4%,the extraradical hyphal length density was between 0 and 149 m/g per gram soil,and the spore density was between 0 and 20 per gram soil.Vegetation types had significant effects on the root length colonization,extraradical hyphal length density and spore density of AM fungi.As a whole,the abundance of AM fungi was highest in alpine steppe and lowest in alpine desert steppe.The total root length colonization of arbuscular mycorrhizal fungi was significantly negatively correlated with soil total nitrogen and organic matter content,while the hyphal length density of roots was significantly positively correlated with the average weight diameter of soil aggregates.(2)A total of 10 families,12 genera and 137 AM fungi species(OTUs)were identified by high-throughput sequencing.Among them.Glomus is the dominant genus of AM fungi in the Qinghai-Tibet Plateau(relative abundance is 43.21%),followed by Rhizophagus(36.92%);at the molecular level,OTU150(Rhizophagus intraradices)has the highest relative abundance(18.19%),followed by OTU225(related to uncultured Glornus sequence,12.45%).By analyzing the spatial distribution of the dominant molecular species,we found that the chemical properties of the soil are the main factors affecting the relative abundance of AM fungi.For example,OTU150 has a positive correlation with the content of nitrogen and phosphorus in the soil,but it is related to soil pH.The average OTUs richness of arbuscular mycorrhizal fungi on our rigion is 23.27,and there are significant differences among different vegetation types.The species richness of AM fungi from high to low is:alpine steppe,alpine meadow,and alpine desert steppe.The correlation analysis showed that the richness of AM fungi was significantly negatively correlated with soil nitrogen content,and had a significant positive correlation with soil pH(3)The composition of AM fungi community was significantly different among different vegetation types,and had significant correlation with soil total nitrogen,soil organic matter,pH and other environmental factors.In the same vegetation type,geographical distance had a significant effect on the community composition of AM fungi,but environmental factors had no significant effect on community composition.In all sites,environmental factors and geographical distance had significant effects on the community composition of AM fungi.However,the influence of geographical distance is slightly stronger than environmental factors.Overall,the community similarity of AM fungi decreased with the increase of geographical distance,showing obvious distance-decay relationship.The above results indicate that the abundance,species diversity and species composition of arbuscular mycorrhizal fungi in the Qinghai-Tibetan Plateau have significant spatial distribution heterogeneity,and this difference is mainly due to the geographical distance,vegetation type,and environmental heterogeneity.The results of this study provide important data for the study of mycorrhizal ecology in alpine regions and provide theoretical basis for further understanding of the diversity of AM fungi and community assembly.Our study provides important technologies for the ecological protection and restoration of the Qinghai-Tibet Plateau. |
PDF Full Text Request