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In order to elucidate the activity and ecological distribution of arbuscular mycorrhizal (AM) fungi in Saibei desert steppe, we sampled soil from three different sites at Erniudian,Shangduzhen and Qinggeletu in Saibei desert steppe in June 2013. Roots of Caragana korshinskii and rhizosphere soil were collected from each site at five depths in the soil profile: 0-10, 10-20, 20-30, 30-40 and 40-50 cm, respectively. The results indicated that C. korshinskii formed strong symbiotic relationship with AM fungi. AM fungal spore density and colonization rates were significantly affected by sampling sites and soil depths. The highest spore density occurred at the 0-10cm layer and gradually decreased with soil depths. Hyphal colonization rate was the highest in samples collected at Shangduzhen among the three sites. However, vesicular colonization was the lowest in samples from Qinggeletu, and there were no significant differences among soil layers. Arbuscular colonization differed among the three sites. Both the total colonization rates and colonization intensity of AM fungi http: / / www.ecologica.cn in root samples from Shangduzhen were the highest compared to the other two sites, respectively. Spore density strongly correlated with soil organic C, total N, easily extractable glomain (EEG) and total extractable glomalin (TG) (all P < 0郾 01) , soil pH (P<0郾 05) , and negatively correlated with available P (P<0郾 01). Hyphal colonization rate had negative correlation with soil pH, available P, total N and acid phosphatase (all P< 0郾 05). Vesicular and arbuscular colonization rates were strongly correlated with available N and alkaline phosphatase (all P<0郾 01). EEG and TG had significant positive correlation with available N, total N, alkaline phosphatase and acid phosphatase (all P<0郾 01) , urease (P < 0郾 05) , but had no significant correlation with available P. Principal component analysis showed that acid and alkaline phosphatase, TG, total N and organic carbon were the key factors affecting soil nutrient status. The average contents of TG and EEG were 3.19 mg / g and 1.17 mg / g accounting for 7.77% and 3.83% of the total soil organic carbon, and 20郾 81% and 9.57% of the total soil nitrogen, respectively. Multiple linear regression analysis showed significant linear correlation between TG or EEG and soil organic C and total N, respectively. The results suggest that AM fungal colonization and glomalin are useful indicators for evaluating soil quality and function of desert ecosystem on the basis of its relationship with AM fungal distribution, soil nutrient dynamics, carbon and nitrogen cycle.

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Ammopiptanthus nanus is the only endangered evergreen broadleaf shrub endemic to the deserts and plays all vital roles, which is thought to be the prefect plant at improving arid desert area and in putting off desertification. To elucidate the colonization rule of AM and DSE fungi and the ecological function of soil factors on Ammopiptanthus nanus, The paper studied the ecological distribution of AM and DSE fungi, and symbiosis with Ammopiptanthus nanus. We sampled from four different sites including Kang Su, Biao Ertuokuoyi (yang) , Biao Ertuokuoyi (yin) and Shang Etushi in XinJiang in June 2012. Soil samples were collected from the rhizosphere of Ammopiptanthus nanus, and were divided into five depth intervals, 0-10, 10-20, 20-30, 30-40 and 40-50 cm respectively. The results indicated that the average total colonizations of AM and DSE fungi were 83.2% and 53.22% respectively. AM and DSE fungi could establish well symbiosis with the roots of Ammopiptanthus nanus. Ammopiptanthus nanus could be highly infected by AM fungi and form a classical type of arbuscular mycorrhizal, most of which is arum type (A鄄type). The spatial distribution of AM and DSE fungi had significant spatial differences. The total colonization of AM fungi in Kang Su and Shang Etushi was highest and reached the peak at the 20-30 cm layer. There were no significant differences in the total colonization of DSE among different soil layers. However, it was higher in Biao Ertuokuoyi(yang) than that in the other three sites. and it was the lowest in Shang http: / / www.ecologica.cn Etushi. The relativity of analysis showed that the colonizations of hyphened,Vesicular colonization and total colonizations of AM fungi had significantly negative correlations with each structures of DSE, such as hypha, microsclerotia and total colonizations. The hypha and total colonizations of DSE had negative correlations with the colonization intensity of AM fungi, and extreme positive correlations with arbuscule colonization. That showed the presence of niche competition between AM and DSE fungi. The infecting of AM and DSE fungi were significantly affected by soil factors. The total colonizations of AM fungi were extreme positive correlations with available P, TG (total glomalin) and acid phosphatase, significant positive correlations with soil urease, and significant negative correlations with soil pH. The hypha colonization were extreme positive correlations with soil urease, TG and acid phosphatase, and significant positive correlations with organic matter and available P. The vesicular colonization was extreme positive correlations with acid phosphatase. The arbuscule colonization was extreme positive correlations with TG, but extreme negative correlations with soil pH, and significant negative correlations with alkaline phosphatase. There were extreme positive correlations between the hypha colonization of DSE and soil urease, and extreme negative correlations between hypha colonization and available N and soil pH. The total colonizations were extreme positive co...