关键词: 最大分子持水量, 毛管上升水, 土壤含水量, 土壤水分特征曲线

Abstract: Water is the restraining factor of vegetation restoration and sand management and the key factor of the ecological environment in areas of desertification. Capillary rising water is one of the primary sources of water for plants. If capillary rising water can reach the active layer of a psammophyte root system and put the plants in hydraulic contact with groundwater,it can provide favorable conditions for the psammous plants to utilize the groundwater. The aims of this paper were to determine the maximum height of capillary rising water in the area of a deep groundwater table in the southern edge of the Gurbantunggut Desert,Xinjiang,China and provide a theoretical basis for the division of the water sources of sand-fixing plants. Three soil moisture monitoring points located at the foot of the west slope,the foot of the east slope,and the flat land on the east side of a dune （i.e.,the lowland between two dunes） were arranged along the cross-section of a fixed dune in the area of a deep groundwater table at the southern edge of the Gurbantunggut Desert. A neutron soil moisture probe was used to observe the soil moisture in the 0-10-m soil profile and to analyze the soil moisture changes of the different slopes of variation over the seasons from March 2016 to November 2018. Then,the pressure membrane meter method was used to determine the soil moisture characteristic curve using the soil samples of the soil moisture monitoring points. Additionally,a method of intersection between the largest molecular moisture holding capacity and soil water content curve was used to determine the maximum height of the capillary rising water at the test site. The results showed that the soil water content of the 0-130-cm soil layer at different slopes of the dune was greatly affected by external meteorological factors and that the law of seasonal change was obvious. The soil layer from 130 to 570-760 cm was a dry sand layer with a stable soil moisture content. The soil water content in the soil layer below 570-760 cm was primarily affected by the fluctuation of the groundwater table and capillary rising water,and the upper boundary of its water content change could be regarded as the maximum height of the capillary rising water. Moreover,the maximum molecular moisture holding capacity of the test site was 0.026 1 cm³·cm^-3,and the maximum height of the capillary water on different slopes of the dune was distributed from 250 to 290 cm. Finally,according to the root distribution characteristics of the constructive species at the test site,this paper preliminarily assumed that such species,e.g.,Haloxylon ammodendron and Haloxylon persicum,can utilize groundwater through capillary rising water.

Key words: maximum molecular moisture-holding capacity, capillary rise, soil water content, soil moisture characteristic curve