Preliminary Research On Sand Intercepting Process Of Vegetation And Currency Valuation For Desertification Hazard

The sand intercepting process is a common and natural phenomenon on the rim of desert especially in the interlaced zones of desert and oasis, meanwhile research on sand intercepting process is of great importance to the protection of desert highway and desert railway, so as to more and more attention has been attached on it. The migration and sedimentation of inattentive sand materials of the underlying earth's surface under the action of the wind is one of the most important reasons which causes the expanding of the sands and the intercepting process of vegetation in arid and semi-arid regions.A great deal of relevant researches on relationship of vegetation and sand transport demonstrates that there is an evident negative relationship between vegetation coverage and sand transport rate, so much so that there is a marginal value on which the sand transport rate reaches 0 with the continuous increasing of vegetation coverage. Based on the fact that there is much more difficulties to conduct a study on measurement of sand transport rate and do research on relationship of vegetation and sand transport rate in field environment, preceding researches mainly adopt wind tunnel simulation experiments, theoretical calculation or numerical simulation. It is capable of Wind tunnel simulation experiments to regulate various experimental conditions effectively, and it is effective to conduct factor analysis, but also it is incompetent to simulate experimental environment which is consistent with that in the field. Theoretical calculation and numerical simulation possess the characteristic of rigorous logicality but frequently lack of the support of field observation data. Based on existed achievements and shortages, it is found that the difficulty in the observation of action of wind-drift sand is the"bottle-neck"which causes relevant researches not deep-going.Aiming at the shortages of preceeding researches, on basis of field experiment, this paper obtained a great deal of primary data by dotty﹑timing and continuous on the spot observation in the field based on which the sand intercepting process of arbor and shrub vegetation was preliminarily discussed. The results show that: to arbor vagetation, vertically, power function with a fitting degree of 0.9845 is optimal to sand trap 1; so far as sand traps 2 and 3 are concerned, optimum fitting functions are repectively quadratic curve function and power function whose fitting degrees are 0.9969 and 0.9947; when sand trap 4 is concerned, the optimum fitting function changes into quadratic curve function with the fitting degree high up to 0.9987. Horizontally, 6 different functions are fitted among which the negative exponential function possesses the highest fitting degree 0.9876 compared with the other 5. It can be seen from the broken line graph for ratio of wind speed values that most of points are in the range of 0.5 and 1.5, exhibiting a symmetric distribution on axis of 1. To shrub vagetation, vertically, optimal fitting results of the sand amount with height H is power function to number 1 sand trap with the fitting degree of 0.9875; fitting degrees of quadratic curve functions are highest to sand traps 2 and 3, which are 0.9677 and 0.9966, respectively; as far as sand trap 4 is concerned, the exponential function, quadratic curve function and stepwise regression fitting function share the same fitting degree which reaches up to 0.9441. Horizontally, the fitting curve of quadratic function optimizes among all 4 different functions and the fitting degree is high up to 0.9967. With regard to the values of wind velocity differences, on the whole, the changes of the values of wind velocity differences present a characteristic of an irregular single waveform pattern. All of the above-mentioned results acquired in this field experiment may provide some practical reference to related research on desertification and the prevention of wind and fixation of sand.To some degrees, the preliminarily discussion on sand intercepting process of arbor and shrub vegetation enriches the content of research on relationship between wind-sand movement and vegetation, meanwhile it provides valuable references to application study sand pretection and sand control.The result of currency valuation for desertification hazard shows that economical loss varies among different afflicted bodies, and different stages of desertification have evident influence on the same afflicted body.