| Degradation of Northern Shanxi Loess Plateau soil water deficit, the vegetation is sparse, but under the sparse vegetation are widely developed in the moss as the main component of biological crust. Its existence on the soil properties change plays an important role. In this study, through field investigation and sampling, and laboratory analysis determination, in-depth study of the distribution and biological characteristics of Northern Shaanxi Loess Plateau of moss crusts, made clear the influence of moss crusts on soil physical and chemical properties; using the water drop penetration time, alcohol solution infiltration method and disc infiltration meter method, the comparative study of the Loess and sand soil moss crusts on soil denounced the influence of water; analysis of moss crusts water repellency on fire, surface active agent and soil water content and other factors of response rules. The results are as follows:1. In Northern Shanxi loess area with microbiotic skin moss crust, and the development status in the sandy soil on the Loess in. In the area of moss crusts has an average thickness of 3.16 mm,18.42±15.9 plants cm-2 moss plant density and biomass for 13.58±1.78 mg cm-2. Moss crust is the main component of the area of biological crusts, the dominant species for polar true moss (Bryum arcticum (R. Brown) B.S.G) and native torsional export moss (barbula vinealis). The wind sand moss crust in the Loess Area in better condition, the distribution is also greater than the loess. Aeolian sandy soil on the growth of moss crusts near the surface, the ground part is low, about 1-2 mm, and loess on the growth of moss crust on the ground are usually higher, about 2-3mm.2. Moss crusts enhances the soil holding water capacity, decreased soil bulk density, increase soil organic matter, total nitrogen and total phosphorus content, the soil pH value decreased. Moss crust after the development of the soil water increased, soil water availability increase. Moss crusts, respectively, for the Loess and aeolian sandy soil two soil texture of the saturated water content were increased by 2.03 and 1.02 times, field water holding capacity were increased by 1.56 and 1.12 times, bulk density were decreased by 20.3% and 17.9%. Soil chemical properties, degree of moss crusts influence on Loess and aeolian sandy soil total nitrogen and organic matter content in the larger, respectively, an increase of 9.61 times, 2.43 and 6.13 times,6.45 times, the total phosphorus content, to a lesser extent, respectively increased 1.81 times,1.74 times. Moss crust soil pH value decreased, a decline of 0.3 to 0.5 units.3 Moss crusts significantly increased the Loess and sandy soil water repellent time, water repellent strength and water repellent coefficient. Two no crust on the soil does not have the water repellency and moss crust development after spending water time, water repellent strength and coefficient of water repellency were significantly increased. Loess of moss crusts average spending time of water 876 s, denounced the intensity of water (alcohol critical solution concentration is 3%, water repellent coefficient is 2.87; and no crust compared, loess of moss crusts denounced the time of water and water repellent coefficient were increased by 5.63 times and 28.7%. Aeolian sandy soil of moss crusts average spending time water was 10.47 s, denounced the intensity of water (alcohol critical solution concentration of 5%, water repellent factor of 2.95; and no crust compared, aeolian sandy soil of moss crusts spending time of water and water repellent coefficient were increased by 3.99 times and 39.8%.4 Fire, surfactant and soil water content were significantly changed the water repellency of the moss crust. Fire significantly enhanced the moss crust water repellency and burning time is longer, and the exclusion of water is stronger, burning time 90s, soil has serious water repellency. Different concentrations of cationic and anionic surface active agent are reduced by moss crusts water repellency and anionic surface active agent strength is higher than that of cationic surfactant. Soil water content significantly changed the moss crust water repellency, spending time with the soil water content showed a single peak curve, denounced water coefficient increases with the increase of soil water content. On the whole, effects of fire factors on the water repellency of the moss crust than the other two factors are more significant.In summary, moss crust formation can increase the soil to water and nutrient content, has a-positive effect on degradation of vegetation restoration and ecological environment construction; therefore, deal with moss crusts of effective protection, and can cultivate the moss crust through artificial inoculation method, thus large scale ecological environmental governance. At the same time, moss crust formation can significantly enhance the soil water repellency, which may influence rainfall into infiltration and surface runoff, in the area of soil and water conservation and ecological environment restoration should be focused on. |
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