Xu Xinwen

Progress in study on irrigation practice with saline groundwater on sandlands of Taklimakan Desert Hinterland

The study on the distribution and dynamic changes of soil moistures and salts under different irrigating methods and managements of using saline groundwater on the sand lands of the hinterland of the Taklimakan Desert, started in 1997. The results show that drip irrigation can be applied to seedlings (furrow irrigation can be applied to level lands) using saline groundwater in the process of constructing the biological shifting sand control system along the desert highway in the hinterland of the Taklimakan Desert; an irrigation frequency of 20 days and an irrigation amount of 30 kg/m2·time are suitable to the shifting sand control forest belts at the same year as they were afforested. Along with the increase of forest age, the irrigation norm can be properly increased, the irrigation interval can be prolonged.

Ecological stability of Tarim Desert Highway shelterbelt

The Tarim Desert Highway shelterbelt, located in hinterland of Taklimakan Desert, is irrigated by underground saline water, with three to thirty gram per litter mineral degrees. The sustainability and stability are affected by multifarious stress. The structural and functional characteristics of shelterbelt are studied to probe into correlation between environment and shelterbelt. On basis, decision analysis is applied to study ecological stability of the Tarim Desert Highway shelterbelt, to screen out limited factors, to establish general index system, and to evaluate the stability of the shelterbelt nowadays. Finally, the concept of ecological stability is utilized to manage the artificial ecosystem. The results show that the artificial ecosystem is relatively flimsy, whose stability can be increased by adjusting stand structure and improving the nutrient cycle.

Analysis on Properties of Topsoil Salinity along the Shelterbelts of the Tarim Desert Highway: Analysis on Properties of Topsoil Salinity along the Shelterbelts of the Tarim Desert Highway

The shelterbelts along the Tarim Desert Highway are faced with serious topsoil salinization and the adaptability of plants irrigated with high-saline water.Based on the field observation,some samples of topsoil and groundwater were collected along the Tarim Desert Highway.According to the analyzed results of 56 soil samples and 49 groundwater samples,in this paper the properties of topsoil salinity along the shelterbelts of the Tarim Desert Highway are discussed.The content,chemical components and spatial distribution of topsoil salinity are analyzed. The results are as follows:(1) The topsoil salinity along the shelterbelts of the Tarim Desert Highway is high because of the high evaporation and severe environment in the Taklimakan Desert;(2) The correlation between electric conductivity and salinity of groundwater is very significant(R~2=0.673).The linear correlation between soil electric conductivity and topsoil salinity is determined,and the dependent equation is developed;(3) High salt accumulation occurs in topsoil,and the total salt content is as high as 257.94 g/kg.The dominant anion from salt in soil is Cl~-,accounting for 54.12%～96.95%of the total anion,and then SO_4~(2-) and HCO_3~-;the dominant cation is Na~+,its proportion is as high as 77.41%～88.53%of the total cation,then Mg~(2+) and Ca~(2+) with proportions of 4.68%～11.90%and 1.08%～8.69%respectively.The correlation coefficient between Na~+ and Cl~-is 0.97 indicating that the dominant soluble salt is NaCl,and then Na_2SO_4,MgCl_2 and CaCl_2.There are high correlations between electric conductivity and concentrations of Cl~-,Na~+ and salt content in topsoil,and their correlation coefficients are 0.862,0.813 and 0.815 respectively;(4) The spatial variability of topsoil salinity,pH value and electric conductivity of topsoil shows that the variation of salinity and electrical conductivity of topsoil is moderate, the variation of pH value is rather weak,and the pH value of topsoil along the shelterbelts of the Tarim Desert Highway increases gradually from north to south.These results are expected to provide some scientific insights on the plant growth of the shelterbelts along the Tarim Desert Highway and the management of groundwater resources, and can also shed a light of the sustainability of shelterbelts along the Tarim Desert Highway.

Effect of Drip Irrigation Water with Different Salinity on Soil Microbe of the Tarim Desert Highway Shelter-Forest

Soil microbes in forest land are crucial to soil development and the production of available nutrients for forest trees in extreme arid areas. In this study, we used FAME and PCR-DGGE to study the effects of saline waters for drip irrigation on soil microbes in the shelter-belt along the Tarim Desert Highway in Northwest China. The main results revealed that differences in the soil microbial amounts, fatty acids and DNA segments among the shelter-belt lands drip-irrigated with different salinity waters were significant, and that the soil microbial amounts, diversities of fatty acid and DNA segments decreased with increasing water mineralization. Investigation of vertical differences in the soil microbial amount and fatty acid composition revealed that the maximum appeared at 5-30 cm, while the minimum was observed in the surface layer. The effects of the soil physical properties on the soil microbes were more notable than those of the nutrient contents. The salt composition form was dominated by Na+-Cl--SO42-, and the content of the SO42- was enhanced with increasing water mineralization. In conclusion, a high degree of mineralization of drip-irrigation water may cause the soil to harden and its quality to degrade gradually, which hinders the growth and development of forest soil microbes.

Change in soil physical and chemical property in the Tarim Desert Highway shelterbelt under saline water drip-irrigation.

Abstract The physical and chemical properties of drip-irrigated aeolian soil with highly saline groundwater in the shelterbelt along the Tarim Desert Highway were investigated. The results show that surface layer litter quantity increases with shelterbelt age. Soil compactness in crust, 0~5 cm, 5~15 cm and 15~30 cm soil layers also decreases with shelterbelt age. Soil organic matter content increases with the shelterbelt age, and on the other hand, gradually reduces from the top to deeper layer of the soil profile. Total salt content decreases with both shelterbelt age and soil depth. Individual ions content in crust layer decreases, that in 0~5 cm, 5~15 cm and 15~30 cm soil layers increases with shelterbelt age. Soil pH in crust, 5~15 cm and 15~30 cm layers decreases with shelterbelt age, while that in 0~5 cm soil layer increases with shelterbelt age. Key words Saline water drip-irrigation, Aeolian soil, Soil physical and chemical property, Tarim, Highway shelterbelt in desert, Taklimakan Desert (Received June 20, 2008; accepted Nov. 17, 2008)