[Soil Stoichiometry Characterization in the Oasis-desert Transition Zone of Linze, Zhangye].

To investigate the changes in C, N, P, and K contents and ecological stoichiometry of desert oasis soils and to elucidate their ecological responses to environmental factors, 10 sample plots were selected in the Zhangye Linze desert oasis in the middle part of the Hexi Corridor, and surface soil samples were collected to determine the C, N, P and K contents of soils and to reveal the distribution characteristics of soil nutrient contents and stoichiometric ratios in different habitats and the correlation with other environmental factors. The results showed that:① the distribution of soil carbon was uneven and heterogeneous across sites (R=0.761, P=0.06). The highest mean value was 12.85 g·kg-1 in the oasis, followed by 8.65 g·kg-1 in the transition zone and 4.1 g·kg-1 in the desert. ② The content of total soil potassium did not vary significantly and was high among deserts, transition zones, and oases and low in saline areas. ③ The mean soil C:N value was 12.92, the mean C:P value was 11.69, and the mean N:P value was 0.9, all of which were lower than the global average soil content (13.33, 72.0, and 5.9) and the Chinese soil average (12, 52.7, and 3.9). ④ Soil water content was the most influential factor affecting C, N, P, K, and ecological stoichiometry characteristics of desert oasis soils, with a contribution of 86.9%, followed by soil pH and soil porosity, with contributions of 9.2% and 3.9%, respectively. The results of this study provide basic information for the restoration and conservation of desert and oasis ecosystems and establish a basis for future study of the biodiversity maintenance mechanism in the region and its correlation with the environment.

[Nitrite denitrification characteristics with redox mediator].

This study optimized the nitrite degradation conditions and explored the characteristics of nitrite degradation with redox mediators and nitrite denitrifying bacteria. The results suggested that the optimal condition of nitrite denitrification was 35 degrees C, pH = 8.0, sodium succinate as the carbon source, the C/N rate of 4 and the initial nitrite concentration of 100 mg x L(-1); the optimal AQS concentration was 0. 16 mmol x L(-1); ORP values stabilized around -400 mV to -500 mV with AQS, which were lower than that of controls during the denitrification process; the pH changed with nitrite removal and stabilized at 9 to 10; through the analysis of denitrifying intermediate metabolites, the impact of AQS on nitrite denitrifying process presumably not only played a coenzyme CoQ role but also accelerated the cytochrome transfer electronic process. This study provides the optimal parameters for practical application of the nitrite biodegradation with redox mediator.

[Biocatalyst of redox mediators on the denitrification by Paracoccus versutus strain GW1].

The quinone respiration process of Paracoccus versutus strain GW1 was characterized and the effects of the four redox mediators on the denitrification process were studied. The experiment results suggested that quinones were utilized by Paracoccus versutus strain GW1 as electron acceptors in the respiratory chain and reduced to hydroquinone. Batch experiments were carried out to investigate the biocatalyst effect of redox mediators as catalyst on the denitrification process at 35 degrees C. All four redox mediators tested were able to enhance the nitrate removal efficiency and the denitrification efficiency by 1.14-1.63 fold and 1.12-2.02 fold, respectively. The accelerating effect from high to low was AQDS > 1,5-AQDS > AQS > alpha-AQS. In the presence of redox mediators, the stabilized ORP values in the nitrate decomposition process were reduced by 33-75 mV. The pH variations in denitrification with redox mediators showed similar tendency to that of the conventional nitrate removal process. In the concentration range of 0-0.32 mmol x L(-1), AQDS had the best accelerating effect and a linear correlation was found for the denitrification rate K and the AQDS concentration cAQDS. This study indicated that the application of redox mediators significantly improved the denitrification process by enhancing the decomposition rate.

[Response of the soil ciliate community to ecological restoration in Huajialing, Dingxi, Gansu].

To obtain a better understanding of the responses of soil ciliate communities to ecological restoration, a quarterly survey of the soil ciliate community and seasonal dynamics across five sampling sites of artificial spruce forest was undertaken. A contrast sampling site of wild grassland was used and live observation ciliates and the three level ten-fold dilution method was used in Huajialing, Dingxi, Gansu. A total of 127 species were identified, belonging to three classes, nine orders, 34 families and 50 genera. Results show that the species distribution had obvious differences across the sampling sites, the community structure of soil tended to be complicated and species comparability decreased gradually with the number of restoration years, and abundance, species richness and species diversity index showed an upward trend. The dominant groups of soil ciliates changed during ecological restoration. Colpodida was the dominant group in sampling site I and site II, whereas Hypotrichida was the dominant group in the late recovery sampling sites. This study shows that the dynamics of the soil ciliate community better respond to soil condition changes in the ecological restoration process. Although the soil ciliate community can be used to evaluate the effect of ecological restoration of terrestrial ecosystems, plenty of further systematic research to establish an effective and feasible evaluation index system is required.

Improvement of the uniformity and dipole ferromagnetism in Co nanodots assemblies on Pb/Si(111) via step tuned dimensionality variation.

We fabricated quasi-one-dimensional Co nanochain assemblies and two-dimensional Co nanodot assemblies on Pb/Si(111) substrates by step decoration. The morphology and magnetic properties of these two kinds of Co nanodot assemblies were investigated by in situ scanning tunneling microscopy and magneto-optical Kerr effect measurements. It was found that the steps cannot only improve the uniformity of the Co nanodots, but also increase the critical temperature T(c). Monte Carlo simulation indicates that the ferromagnetism mainly originates from the dipolar interactions and the critical temperature T(c) can be enhanced by introducing an in-plane uniaxial magnetic anisotropy via the step tuned dimensionality variation of the nanodot assemblies.