| Arbuscular mycorrhizal fungi (AMF), a kind of soil fungi widely distributed in continental ecosystem, can form symbiotic relationships with the roots of host plant. AMF play important roles in promoting plant nutrient uptake, keeping the ecological stability of rhizospheric microbe. However, little is known about the functions of AM in ecological restoration and vegetation reconstruction of the Loess Plateau. In our study, the mutualistic relationships among Sophora davidii hosts, AMF and some soil factors, such as soil enzymes, glomalin related soil proteins (GRSP) were analyzed. And the AMF diversity in the rhizosphere of Sophora davidii was investigated by Degeneration Gradient Gel Electrophoresis (DGGE). We also used canonical correspondence analysis (CCA) to describe the relationship between the AMF community and environmental factors.The main conclusions included as follows:(1) The average colonization rate of AMF was up to 74.42%, the average spore density was out to 19.06 per gram soil, and the mean of glomalin total was 2.32 mg/g, accounting for 36.46% of soil organic carbon. The colonization rate of AMF did not significantly correlate with the spore density. The distribution of spore density and glomalin exists spatial heterogeneity. Glomalin was positively correlated with soil organic carbon, available N and Olsen P (P<0.01), and negatively correlated with pH. Meanwhile, glomalin was remarkably correlated with soil enzyme activities. The results shows the soil factors were strongly correlated with AMF, and spore density and glomalin were useful indicators for evaluating soil quality.(2) The study suggests that the spore density and AMF colonization both had significantly seasonal difference in the rhizospheres of Sophora davidii and Rosa hugonis. Their total colonization rate were both over 70%, and were markedly higher in August than any other month, while the spores density reached a maximal value in October and minimal value in June. The content of GRSP was seasonal, it ascended first and then descended. In the rhizosphere of Sophora davidii, both the content of easy extract glomalin related soil proteins (EE-GRSP) and total extract glomalin related soil proteins (T-GRSP) reached a maximum in August, while in the rhizosphere of Rosa hugonis they reached a maximum in June and minimum in April. By using stepwise regression analysis, the major factors of AMF colonization were monthly average temperatures, soil available N and soil Urease; Available N and AMF colonization have a negative correlation with it. And the main factors influenced the spores density were soil organic carbon (SOC), Olsen P and Catalase; and SOC was negatively correlated with the spore density.(3) Total DNA was successfully extracted from the soils by alkaline lysis method which taken from the rhizosphere of Sophora davidii. And then, 18S rDNA segments of the total DNA of AMF were amplified by the specific primers using nested-PCR. Finally, the fragments we got were about 210 bp, and then we obtained a clearly molecular fingerprint of DGGE by adopting 8% gel and denaturing solution from 30% to 70%. Through the diversity analysis we learned that biodiversity was obviously different from place to place. Species richness and Shannon-Weiner index in Chunhua and Hanchen of GaoYuan region were higher than those in Zhidan, Ansai and Yanchang of Hilly-gully region.(4) Canonical correspondence analysis (CCA) demonstrated that soil environment had obvious effect on the community composition of AMF. The changes in community composition showed some special heterogeneity along with the change of environmental factors, such as the content of soil pH, SOC, Olsen P, GRSP, the activities of soil enzyme, and the spore density. |
