分类： 地球科学 >> 地球科学史 提交时间： 2018-10-29 合作期刊: 《干旱区科学》
摘要： Salt-affected soils are mostly found in irrigated areas within arid and semi-arid regions where the groundwater table is shallow. Soils of this type have become an increasingly severe problem because they threaten both the environment and the sustainable development of irrigated agriculture. A tool to estimate phreatic evaporation is therefore urgently required to minimize the salinization potential of salt-affected areas. In this context, phreatic evaporation at zero water table depth (E0) is a key parameter for establishing a model for calculating phreatic evaporation. The aim of this study was to explore the law of phreatic evaporation and to develop structurally rational empirical models for calculating phreatic evaporation, based on E0 data of six types of soil (i.e., gravel, fine sand, sandy loam, light loam, medium loam, and heavy loam) observed using the non-weighing lysimeter and water surface evaporation (E601) data observed using a E601 evaporator of same evaporation area with a lysimeter-tube at the groundwater balance station of the Weigan River Management Office in Xinjiang Uygur Autonomous Region, China, during the non-freezing period (April to October) between 1990 and 1994. The relationship between E0 and E601 was analyzed, the relationship between the ratio of E0 to E601 and the mechanical compositions of different soils was presented, and the factors influencing E0 were discussed. The results of this study reveal that E0 is not equal to E601. In fact, only values of the former for fine sand are close to those of the latter. Data also show that E0 values are related to soil texture as well as to potential atmospheric evaporation, the ratio of E0 to E601 and the silt-clay particle content (grain diameter less than 0.02 mm) is negatively exponentially correlated, and that soil thermal capacity plays a key role in phreatic evaporation at E0. The results of this analysis therefore imply that the treatment of zero phreatic depth is an essential requirement when constructing groundwater balance stations to study the law of phreatic evaporation
分类： 环境科学技术及资源科学技术 >> 环境科学技术基础学科 提交时间： 2019-10-26 合作期刊: 《干旱区科学》
摘要： Soil moisture is critical for vegetation growth in deserts. However, detailed data regarding the soil moisture distribution in space and time in the Gurbantunggut Desert of China have not yet been reported. In this study, we conducted a series of in situ observation experiments in a fixed sand dune at the southern edge of the Gurbantunggut Desert from February 2014 to October 2016, to explore the spatio-temporal variation of soil moisture content, investigate the impact of Haloxylon ammodendron (C. A. Mey.) Bungeon soil moisture content in its root zone, and examine the factors influencing the soil moisture spatial pattern. One-way analysis of variance, least significant difference tests and correlation analysis were used to analyze the data. The results revealed that the soil moisture content exhibited annual periodicity and the temporal variation of soil moisture content throughout a year could be divided into three periods, namely, a moisture-gaining period, a moisture-losing period and a moisture-stable period. According to the temporal and spatial variability, the 0–400 cm soil profile could be divided into two layers: an active layer with moderate variability and a stable layer with weak variability. The temporal variability was larger than the spatial variability in the active layer, and the mean profile soil moisture content at different slope positions displayed the trend of decreasing with increasing relative height and mainly followed the order of interdune area>west and east slopes>slope top. The mean profile soil moisture content in the root zone of dead H. ammodendron individuals was significantly higher than that in the root zones of adult and young individuals, while the soil moisture content in the root zone of adult individuals was slightly higher than that in the root zone of young individuals with no significant difference. The spatial pattern of soil moisture was attributable to the combined effects of snowfall, vegetation and soil texture, whereas the effects of rainfall and evaporation were not significant. The findings may offer a foundation for the management of sandy soil moisture and vegetation restoration in arid areas.
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