Effect of chemical and organic fertilization on soil carbon and nitrogen accumulation in a newly cultivated farmland

Increased food demand from the rapidly growing human population has caused intensive land transition from desert to farmland in arid regions of northwest China. In this developing ecosystem, the optimized fertilization strategies are becoming an urgent need for sustainable crop productivity, efficient resources use, together with the delivery of ecosystems services including soil carbon（C） and nitrogen（N） accumulation. Through a 7-year field experiment with 9 fertilization treatments in a newly cultivated farmland, we tested whether different fertilizations had significant influences on soil C and N accumulation in this developing ecosystem, and also investigated possible mechanisms for this influence. The results showed that applying organic manure in cultivated farmland significantly increased the soil C and N accumulation rates; this influence was greater when it was combined with chemical fertilizer, accumulating 2.01 t C and 0.11 t N ha^（–1） yr^（–1） in the most successful fertilization treatment. These high rates of C and N accumulation were found associated with increased input of C and N, although the relationship between the N accumulation rate and N input was not significant. The improved soil physical properties was observed under only organic manure and integrated fertilization treatments, and the significant relationship between soil C or N and soil physical properties were also found in this study. The results suggest that in newly cultivated farmland, long term organic manure and integrated fertilization can yield significant benefits for soil C and N accumulation, and deliver additional influence on physical properties.

Microstructure and mechanical properties of Mg-5Li-1Al sheets prepared by accumulative roll bonding

Ultrafine-grain and high-strength Mg-SLi-1Al sheets were prepared by accumulative roll bonding （ARB） process. Evolution of microstructure and mechanical properties of ARB-processed Mg-5Li-1Al sheets was investigated. Results show that, during ARB process, the evolution of deformation mechanism oft Mg-5Li-1Al alloy is as follows： twinning deformation, shear deformation, forming macro shear zone, and finally dynamic recrystallization （DRX）. The grain refining mechanism changes from twin DRX to rotation DRX. With the increase in ARB cycles, strength of the Mg-5Li-1Al sheets is enhanced, whilst elongation varies slightly. With the increase in rolling cycles, anisotropy of mechanical properties decreases. It is conclusive that strain hardening and grain refinement dominate the strengthening mechanism of Mg-5Li-1Al alloy.

Mechanical Properties and Microstructure Evolution of AA1100 Aluminum Sheet Processed by Accumulative Press Bonding Process

Accumulative press bonding（APB） is a novel variant of severe plastic deformation processes,which is devised to produce materials with ultra-fine grain.In the present work,the mechanical properties and microstructural evolution of AA1100 alloy,which is produced by APB technique,were investigated.The study of the microstructure of AA1100 alloy was performed by optical microscopy.The results revealed that the grain size of the samples decreased to 950 nm after six passes of APB process.The yield strength of AA1100 alloy after six passes of the process increased up to 264 MPa,which is three times higher than that of the as-cast material（89 MPa）.After six passes,microhardness values of AA1100 alloy increased from 38 to 61 HV.Furthermore,the results showed that the behavior of variations in mechanical properties is in accordance with the microstructural changes and it can be justified by using the Hall-Patch equation.Moreover,the rise in the yield strength can be attributed to the reduction in the grain size leading to the strain hardening.

Hylocomium splendens (Hedw.) B.S.G.and Pleurozium schreberi (Brid.) Mitt.as trace element bioindicators:Statistical comparison of bioaccumulative properties

The principal objective of this study was to compare bioaccumulative properties of two terrestrial moss species Hylocomium splendens and Pleurozium schreberi from the Kielce area （south-central Poland）, using various statistical techniques. Forty-six moss samples from 23 sampling sites located within the city limits were analyzed for 33 trace elements. The results indicated that 17 elements （Ba, Ce, Co, Cu, Eu, Fe, Gd, Hg, La, Mo, Nd, Ni, Pb, Pr, Sm, V, Y） dominated in H. splendens, whereas only three elements （Mn, Sr, Zn） occurred in excessive amounts in P. schreberi. No differences in the distribution pattern of Dy, Er, Ho, Sn, Tb, Th and Yb were observed. The element concentration ratio （PI/Hy） varied from 0.50 to 1.19. For 14 elements （Ce, Co, Cu, Fe, Gd, Hg, La, Mo, Nd, Ni, Pb, Sm, Th, V）, PI/Hy 〈 1; for 4 elements （Cd, Mn, Sr, Zn）, PI/Hy 〉 1; for 7 elements （Ba, Dy, Er, Eu, Pr, Y, Yb）, PI/Hy = equalled 1. Czekanowski＇s method showed similarities in rare earth element concentrations for both moss species. The cluster analysis exhibited three significant clusters at D link /D max × 100 〈 50 for both moss species. Strong positive Spearman correlations between both moss species were recorded for the following pairs：Ba-Ba, Co-Co, Er-Er, Eu-Eu, Gd Gd, Mn-Mn, Ni-Ni, Pb-Pb, Pr-Pr, Sm-Sm, Th-Th, Y-Y, and Yb-Yb. Nonparametric tests （Sign test, Wilcoxon tests） showed statistically significant differences only for Cd, Ce, Co, Cu, Hg, Mo, Ni, Pb and Sr. The scanning electron microscope study of H. splendens and P. schreberi revealed a different morphology of these species with no injuries.