Study On The Soil And Water Conservation Function Of Microbiotic Soil Crusts On Loess Area Of Northern Shaanxi Province

For further study on the soil and water conservation function of microbiotic soil crusts in Loess areas,based on a large number of collecting date from investigation in WU-Qi,made anti-scouring experiments of microbiotic soil crusts,and analysed microbiotic soil crusts physical and chemical properties and distribution on Loess area of northern Shaanxi province.It gives an important reference value for the soil erosion controlling in Loess Area.The major conclusions are as follows:Analysis on physicochemical characteristics of the microbiotic soil crusts indicated different types of microbiotic soil crusts had nutrients enrichment,except the potassium content.Cu,Cr and Ca was the important factor to the distribution of microbiotic soil crusts.Microbiotic soil crusts can reduce the soil pH value.The average thickness of microbiotic soil crusts can reach 3.67 mm,the coverage of crusts was not higher than 30%;microbiotic soil crusts composed of fine sand particles(0.05-0.01mm) and coarse silt(0.25-0.05mm).Microbiotic soil crusts had changed the soil sand,silt and clay content,and K value,which can impact the soil anti-erosion ability.The factors influencing the distribution of microbiotic soil crusts indicated the coverage of microbiotic soil crusts on north-facing slope and semi-north-facing slope was larger than on south-facing slope and semi-south-facing slope;larger on gully-slope than ridge-slope than the top of slope;the microbiotic soil crusts cover decreased as the gradient increasing,and while it increased later. Microbiotic soil crust cover was increasing with vegetation cover and decreasing during 50%～60% vegetation cover.The coverage of microbiotic soil crusts was shown as to:the herb-based one＞the tree-based one＞the tree-based one.Microbiotic soil crusts cover and littler cover on south-facing slope and semi-south-facing slope was inhibiting,but the relation of that on north-facing slope and semi-north-facing slope was stimulating.The overage of microbiotic soil crustss on slopes with a low disturbance degree is larger than that with a high one.Anti-scourability experiment of microbiotic soil crusts indicated the moss content in microbiotic soil crusts was an important anti-scourability factor and had a negative correlation with sediment concentration,while a positive correlation with the time of microbiotic soil crusts collapsing.During the process of scouring,sediment concentration increased with scouring time,and decreased after microbiotic soil crusts collapsed.Anti-scourability had quadratic relationship with scouring time.As the microbiotic soil crusts collapsed with time,anti-scourability decreased.The coverage of microbiotic soil crusts had a negative correlation with sediment concentration,i.e.the higher the coverage was,the lower the soil erosion was.Slope had a positive correlation with sediment concentration.The erosion rate for soil without crusts covering was 35 times of that with a fully covered surface.