Xiao Honglang

Effects of soil properties on ammonia volatilization

Abstract By using a small culture dish located above a large-sized closed dish with soil samples to trap emissions as well as applying multivariate analysis methods, the influence of soil properties on ammonia volatilization and their correlation was studied. The results showed that the ammonia volatilization rates were positively correlated with the soil pH, CaCO3, and total salt contents but negatively correlated with the organic matter content, CEC, and clay content. Of the three negative correlation factors, the CEC was most highly correlated with ammonia volatilization, while among the three positive correlation factors, the pH predominated. These results enabled to assess the magnitude of ammonia volatilization from soils. According to the correlation equation of ammonia volatilization versus pH and CEC, the potential of ammonia volatilization of some soils in China was determined and the soils were divided into four groups. It was concluded that by increasing the application rate of organic matter ammonia volatilization might decrease.

Modeling the Effects of Crust on Rain Infiltration in Vegetated Sand Dunes in Arid Desert

Shapotou Desert Research Station is located at the southeast edge of Tengger Desert in China. Shapotou sand dunes have been vegetated to stabilize them. The vegetated dunes have been completely covered by a natural crust. Rain infiltration was reduced by 36 % to 74 % on the crusted site while there was no reduction of rain infiltration on the sandy site. The infiltration rate was positively correlated with total rainfall and negatively correlated with rain intensity. Runoff on the crusted site provided water for vegetation growth in the hollows between sand dunes. The crust significantly impeded increased soil moisture. To increase soil moisture in the surface 40 cm layer, rainfall had to be above 8.5 mm on the slopes of sand dunes on the crust site, and increased with rain intensity. In the Shapotou area, the amount of rainfall that vegetation on slopes of sand dunes could utilize, was reduced to about 40 mm per year by the crust, although the mean annual precipitation was approx imately 180 mm. It is ex...

Abiotic Soil Crust Formation on Dunesin an Extremely Arid Environment: A 43-year Sequential Study

The spatial and temporal patterns of soil crust formation on stabilized dunes at Shapotou, northwestern China, were studied on a time sequence of 0, 18, 35, and 43 years. The spatial pattern of soil formation was estimated by measuring the thickness of accumulated sand fractions on the stabilized dune surface and by analyzing the particle size distribution of soil crust. The results showed that the materials forming the embryonic crusts did not come entirely from atmospheric dustfall, but more likely originated from the deflation process of shifting sand and were related to the characteristics of shifting sand particles. Irrespective of the age, all crusts contained a relatively large proportion of 0.01-0.05 mm particles, suggesting that the 0.01-0.05 mm particles provide a material basis and are a prerequisite to the formation of soil crusts. The formation of crust was a sorting and accumulation process of 0.01-0.05 mm particles. Simultaneously, the formation of stable soil crust apparently tended to be subjected to aggregation processes that include aggregation of inorganic particles themselves and aggregation of organic and inorganic particles. The soil crust was in a constantly alternating process of formation and disruption. The alternation period was about one year. Through this alternation, the fine soil layer beneath the crust can be continuously widened and thickened with increasing stabilization time.

Internal structure and trend of glacier change assessed by geophysical investigations

Ground-penetrating radar (GPR) is a useful tool for mapping the thickness, morphology and structure of alpine glaciers. Englacial information obtained during a field survey of the Koxkar Glacier in Tian Shan, China, in June 2008 was retrieved from GPR profile data. At least four specific types of structures can be identified from the GPR reflection image: (1) hyperbolae from point sources, (2) irregular linear distributed features, (3) a dense chaotic return zone above a clearly defined bed reflection and (4) linear reflection within the ice body. The interpretation of a typical GPR image was validated using waveform analysis and a finite-difference time-domain numerical model. Through a series of data analyses, these types of reflection characteristics were strongly related to englacial melting. Considering also the GPR result of the debris thickness distribution at the terminus, it is concluded that strong glacial ablation does not occur at the terminus but at a position higher than the terminus where there is a thin layer of debris and relatively high temperatures. Meanwhile, there are many lakes receiving mostly englacial discharge that greatly erode the ice body through melt-water discharge in some regions, and a thick layer of debris insulating the ice body at the terminus; these features may differentiate the retreat of the Koxkar Glacier from the general retreat of glaciers. In the future, with the ablation of glaciers, the central positions of intense ablation may be disconnected and there may be a dead zone at the terminus.

Development strategies of water and land resources in the hexi region, China

Hexi region is located in the northwest arid zone in China, being both the base of industry and agriculture, and the prop of developing northwestern China on a large scale in the next century. On the basis of the study on exploitation and utilization process of water and land resources in past 40 years, and present productivity, this paper approaches the utilization trend and development potential of water and land resources; analyses the characteristics, problems and directions of resource utilization in the future; and proposes the countermeasures of rational development of water and land resources.

Leaf stable carbon isotope composition in Picea schrenkiana var. tianschanica in relation to leaf physiological and morphological characteristics along an altitudinal gradient

To understand the effects of leaf physiological and morphological characteristics on δ13C of alpine trees, we examined leaf δ13C value, LA, SD, LNC, LPC, LKC, Chla+b, LDMC, LMA and Narea in one-year-old needles of Picea schrenkiana var. tianschanica at ten points along an altitudinal gradient from 1420 m to 2300 m a.s.l. on the northern slopes of the Tianshan Mountains in northwest China. Our results indicated that all the leaf traits differed significantly among sampling sites along the altitudinal gradient (P<0.001). LA, SD, LPC, LKC increased linearly with increasing elevation, whereas leaf δ13C, LNC, Chla+b, LDMC, LMA and Narea varied non-linearly with changes in altitude. Stepwise multiple regression analyses showed that four controlled physiological and morphological characteristics influenced the variation of δ13C. Among these four controlled factors, LKC was the most profound physiological factor that affected δ13C values, LA was the secondary morphological factor, SD was the third morphological factor, LNC was the last physiological factor. This suggested that leaf δ13C was directly controlled by physiological and morphological adjustments with changing environmental conditions due to the elevation.

Element concentration and composition of atmospheric aerosol on southeastern edge of Tengger desert, Shapotou, China

Physi-chemical characteristics of dust aerosol in Northern China and its impact on climate are recognized as an important issue. However, long term dust aerosol observation is scarce. A field measurement of dust aerosol was conducted in Shapotou since March 2001. Total suspended particles were collected by High Volume sampler. Elements in aerosol were analyzed with method of neutron activation analysis (NAA). The results of Factor Analysis showed that two uncorrelated factors accounted for more than 95% of the overall variance. The first factor correlated with Al, Ca, Mg, Mn, Na, Ti, V, Ba, Ce, Co, Cr, Cs, Eu, Fe, Hf, Lu, Rb, Sc, Th, and Yb and explained 86.12% of the total system variance, which are mainly soil related elements. The second factor, which explains 9.753% of the total system variance, seemed to express the source of anthropogenic influence (Sb and Zn). Two groups of elements were characterized by different seasonal variation. The highest concentrations of 20 elements quantified in the TSP samples generally occurred during spring and the lowest in autumn with the exception of Sb and Zn. however, Sb and Zn showed the lowest concentration in summer and the highest in winter. Keywordselemental composition; aerosol; Shapotou; neutron activation analysis