Research On Soil Water Character Of Different Types Of Surface In South Edge Of Mu Us Sandy Lands

Biological crusts are organic complex which is formed by microorganisms, algae, lichen, moss plant and its secretion cemented with soil particles. It is widely distributed in the arid, semi arid region, whose distribution area makes up 40% of biological covering area. The formation and development of biological crusts has important effects on desert landscape process in different bio-climatic zone, soil ecological process, soil hydrological process, soil biological processes and geochemical cycling process and the ecological restoration process in arid, semi arid area. Based on this, on the south edge of Maowusu area, different types surface layers’ soil water characteristics such as bare sand surface in this paper, light grey algae, black and brown algal crusts and mosses crusts are researched in the paper to provide the scientific data for the ecological restoration of damaged system process.This paper takes the development of biological crust in south edge of Mu Us Sandy lands as the research object, through field continuous monitoring, rainfall simulation experiment and laboratory determination and analysis, analyzing of influence of different kinds of biological crusts on surface soil physical and chemical properties of the rainfall water supply for different surface soil influence, interaction relationship and to further explore the different biological node crust and soil water. The main results are as follows:1. Compared with the bare sand, 3 kinds of biological crust on the surface of soil increase the silt and clay content, bare sand medium and fine sand content accounts for particle size range of 90.86%; The content of medium and fine sand in the light grey algae crusts is 82.99%; The content of medium and fine sand in the dark brown algae crusts is 80.38%; The content of medium and fine sand in the mosses crusts is 49.75%. The silt of light grey algae crusts, dark brown algae crusts and mosses crusts were increased by 1.91%, 1.37%, 15.08%, Mosses crusts increase in clay content, about 2.22%. Biological crusts have affected the saturated water content of surface soil, for the performance of bare sand < grayish algae crusts < black brown algae crusts < moss crust; The soil bulk density of different types of biological crust has the difference, the higher the degree of development of biological crusts, the lower soil bulk density is, the performance for the moss crust < light grey algae crusts < black brown algae crusts < bare sand; Soil bulk density with the increase of soil depth on the vertical distribution shows increasing trend.2. In the 0-5 cm soil layer, the moisture contents of light grey algae crusts, dark brown algae crusts and mosses crust are 1.25, 1.41, 1.21 times of the bare sand. In the 5-10 cm soil layer, the moisture contents of light grey algae crusts, dark brown algae crusts and mosses crust are 1.56, 1.57, 1.86 times of the bare sand. In the 10-20 cm soil layer, the moisture contents of the bare sand are 1.52, 1.56, 1.27 times of light grey algae crusts, dark brown algae crusts and mosses crust. Different types of surface capillary moisture capacity, field capacity, saturated water holding variation is not obvious, essentially unchanged. Capillary porosity of different types of surface increased with the soil depth is presented first increasing and then decreasing trend.3. After rainfall, the depth of soil moisture content relate to the biological crust type, development level, the lower the soil texture and physical and chemical properties. In the 10 cm soil depth, the strength of soil water retention properties and the size of water are: moss crusts > bare sand > light gray algae crusts > dark brown algae crust. Soil water retention properties of algae crusts is the lowest, and the mosses crusts is the highest. Soil water retention property of mosses crusts is 1.02, 1.1, 1.35 times of bare land, light grey algae crusts and dark brown algae. Water infiltration intensity is related to the crust development degree. Different biological crusts at different depths in the infiltration performance have different strength.4. Different types of surface soil moisture in reducing at rainfall 0-60 hours after period of time changes with time were all increased firstly and then. In 20 cm soil layer, the water content variation is significantly after a rainfall of 12 h. The moisture content of bare land is 1.5 times before rainfall. Light grey algae crust is 1.4 times before rainfall. Dark brown algae crust is 1.28 times before rainfall. Mosses crust is 1.33 times before rainfall.5. There has different textures in various types of land surface; from lowest to highest are bare land, light gray algae crusts, dark brown algae crusts and mosses crusts. The water holding capacity of light gray algae crusts, dark brown algae crusts, and mosses crusts is about 1.3, 1.7 and 2 times as bare land. The results indicated that the water holding capacity of different types of land surface was enhanced by the development of crusts. The measured curve was in an S-shaped distribution. After comparison, absorption curve had a more significant hysteretic nature than desorption curve. The date of the experiment was estimated by the v-G model which had high goodness of fit for that data and the fitting coefficients are less than 0.009. The results showed that the model which applies to the soil of Mu Us sandy lands can simulate the characteristic curve. The results help to a comprehensive understanding of the hydrological effect of biological crust, having practical significance for the ecological restoration of damaged system.