Diversity And Spatio-Temporal Distribution On AM Fungi Associated With The A.Sphaerocephala And A.Ordosica In Desert

In a rigorous desert ecosystem, the symbiosis between arbuscular mycorrhizal (AM) fungi and plants plays a vital role in improving plant drought tolerance and mineral nutrients uptake. Clonal plants occupy new ecological niche by root-sucker reproduction surviving sand burying, which also provide special environment for AM fungi. As fine semi-shrubs for sand fixation in northern China desert, Artemisia ordosica and Artemisia sphaerocephala are typical phalanx clonal plants. Despite their own physiological characters, their endurance capability for the atrocious circumstance also rest with their symbiosis with AM fungi. In this research, soil samples in the rhizosphere of A.ordosic and A.sphaerocephala were collected to isolate arbuscular mycorrhizal (AM) fungi. The spatial and temporal variation and diversity of AM fungi were determined; correlations between distribution of AM fungi and soil factors, soil glomalin concentration were systemically analyzed. Results were shown as follows:An abundant diversity of AM fungi was found in sandland. 37 AM fungi taxa in five genera were isolated and identified, of which 54% belong to the genus Glomus, 32.4 % to Acaulospora, 8.1 % to Scutellospora,others to Diversispora and Paraglomus. Five uncertain species were identified as unrecorded species. It is the first time to report G.coremioides existing in desert.Dominant species of AM fungi in the rhizosphere of different host plants were different, A.bireticulata, D.etunicatum and G.geosporum were the dominant species in the rhizosphere of A. ordosica. A.bireticulata, A. laevis, G. claroideum and G. convolutum were the dominant species in the rhizosphere of A.sphaerocephala.The community members and species richness of AM fungi were also different among sampling sites and soil depths due to soil properties and microenvironment. The most species was found in Yanchi site, while dominant community of AM fungi mainly distributed in 0-20cm soil profile.Both two host plants can form well symbionts with AM fungi in desert. The total colonization of AM fungi of A. ordosica was 89.94%, and that of A.sphaerocephala was 94.98%, both of them formed the intermediate type mycorrhizas.The colonization of hyphae and vesicles were higher in 0-40cm soil layer than that in 40-50cm. The arbuscular colonization was higher only in 10-40cm soil layer.Geographical and environmental factors affected the diversity of AM fungi and colonization of arbuscular mycorrhiza. Both soil fertility and soil enzyme activities were negatively correlated with arbuscular colonization.On the flowing dunes where soil was infertile and serious drought, the spore density was lower but arbuscular colonization were higher.The maximal value of spore density was observed at the 0-10cm layer, and then gradually decreased with soil depth. The soil enzyme activities showed the same trend with the spore distribution. Seasonal variation of spore density in the rhizosphere of phalanx clonal plants was found; the highest value appeared in summer. The spore density was different among sites, and was significantly and positively correlated with soil available P, N, organic matter contents and soil enzyme activities.Total Glomalin concentrations in the rhizosphere of A.ordosica ranged from 0.35 to 4.40mg/g, Easily Extractable Glomalin concentrations ranged from 0.29 to 0.92mg/g. glomalin concentrations showed a clear pattern of decrease from 0 to 50cm soil layer in every site and decline trend with season change, the maximal value was in spring. Glomalin concentrations were significantly positively correlated with soil fertility, microbial activity and spore density, suggesting that glomalin can be used as a new indicator to monitor desertification and soil degradation. We have determined the Glomalin concentrations in desert, which has not been reported yet by the national peers before.The results showed that both Artemisia ordosica and Artemisia sphaerocephala could establish well symbiosis with AM fungi, which was the main reason for maintaining integrity and stability of the desert ecosystem, elucidated the ecologic function of AM fungi and interaction between host plants and AM fungi, provided the scientific basis for the applications of AM biotechnology in vegetation restoration and ecology reconstruction of desert.