| Wind erosion is an important factor of the process desertification in arid, semi-arid and humid areas, result in the region resources and the environment develop slowly. Caragana intermedia Kuang et H.C.Fu is a kind of deciduous shrubs, it is a tree to sand-fixing, soil and water conservation in northern China, which is playing an important role in soil erosion and prevention of desertification. This article chosen the shrubs of Yanchi County as the main object of study, which located in the southern edge of the Mu Us Sandland and Loess Plateau area. Taking the wild wind erosion continuous observation, erosion sample ascertains by measuring indoor, with remote sensing of vegetation basic dynamic monitoring, combined with sand physics and restoration ecology theory, to analyse the amount of soil erosion at different heights and dynamic response characteristics between the lines of the shrubs, and response of the wind speed and direction, make the quantitative evaluation of its effect to control soil erosion. Using the analytic hierarchy process from the plot scale to analysis of the effects of different factors on soil erosion, as well as to wind erosion monitoring center set point in different directions along the transect, vegetation changes comp table with the mainland-based remote sensing technology, the main analysis caragana landscape units vegetation heterogeneity on the role of soil erosion from the landscape scale, in order to quantitatively evaluate the shrubs, windbreak and sand effects and scientific management to provide a theoretical basis. The main results and draw the following conclusions:(1) The annual average wind speed in the study area is1.98m/s, wind speed showed some seasonal regular pattern, the mean of wind speed gradually increases in spring, to June reached the maximum. Wind speed greater than3.4m/s wind concentrated in the spring, wind speed above on the8.0m/s wind appears only in the spring. Seasonal changes of wind speed is one of the factors leading to the quantities of soil erosion also showed seasonal variation.(2) The dominant wind direction of study area in January to May is WNW-W, June to September dominant wind direction is S-SSE, October to November dominant wind direction is SW-SSW, December dominant wind direction is WSW. The research and analysis the dominant wind direction to help guide the caragana shelterbelt construction in study area, according to the prevailing wind direction to adjust the planting of vegetation, while the vegetation grow in wind direction and desertification space spatial heterogeneity of soil erosion is largely effects.(3) The things of soil erosion of the bottom on moving dune current monthly increases with height and descending, of which90%concentrated in the0～50cm, the quantities were significantly increased in March, April, May, representing the total annual erosion74.4%. Caragana line in16a,25a,37a, between the volume of soil erosion performance over time showed a decreasing trend after the first increases, and soil erosion in mid-May of the year to reach the maximum volume, since the times of the scarce rainfall in the study area, and caragana not fully germinate and vegetation, combined with increasing wind speed leads to erosion of the largest mid-May. (4) The things of soil erosion of the16a,25a,37a Caragana Kuang et H.C.Fu are spring>summer> autumn>winter. Because the vegetation growth has certain seasonal, while rainfall concentrated in autumn, and the seasonal wind speed, makes the research of soil erosion has obvious seasonal change, and not the same amount of wind erosion in spring were significantly higher than in other seasons, soil erosion that the most in spring. If we want to obtain the effective prevention and control of soil erosion to carries on the key monitoring in the spring.(5) The things of soil erosion of the artificial Caragana forest are mainly controlled by the wind speed, surface soil moisture and vegetation coverage and other factors, precipitation, vegetation canopy and soil surface temperature will cause a certain degree of influence on wind erosion amount. It is difficult to change the wind speed and soil water content, so we can reduce soil erosion by increasing the coverage of vegetation in the process of wind erosion.Therefore, Caragana Kuang et H.C.Fu as survivability strong vegetation in arid area can play an important role in wind erosion; vegetation canopy can also have the indirect effect of wind erosion process, so in the vegetation of wind erosion prevention, as far as possible to maintain the vegetation canopy size, can further reduce the amount of wind erosion in the vegetation on prevention of soil erosion process, in order to enhance the role of windbreak and sand fixation.(6) Both the content of organic carbon and nitrogen of different height soil wind erosion matter of16a,25a,37a Caragana intermedia Kuang et H.C.Fu were higher than in surface soil, migration of surface soil is larger than that of organic carbon, soil nutrient loss to total nitrogen; with the increase of planting age, soil organic carbon and total nitrogen content increased, while the wind erosion matter originates from the surface, organic carbon and total nitrogen content of wind erosion also showed a trend of increase, and the same period along with wind monitoring height increasing.(7) For erosion monitoring point as the center along different directions in sample belt, vegetation spatial heterogeneity on wind erosion,results show that different direction transect vegetation heterogeneity in the same direction under the action of wind, could lead to soil erosion effect of Caragana Kuang et H.C.Fu plot significantly change, indicates that the landscape pattern heterogeneity of Caragana Kuang et H.C.Fu as subject to wind erosion effect is significant. We can apply to the spatial pattern of landscape scale configuration, to play sand fixing effect of Caragana microphylla in a more effective in afforestation and forest management process. |
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