Research On Farmland Wind-Sand Disaster Of Oasis And Its Control Mechanism In Ulan Buh Desert

Oasis is the most important eco-economic area in Ulan Buh Desert. Wind-sand disaster is severely threatening the normal function of oasis farmland. To ensure the sustainable development of oasis agriculture, research on wind-sand disaster of oasis farmland and its control mechanism was carried out with methods of field test, wind tunnel simulation and laboratory experiment. The main research results are:(1) Division of oasis function areas and farmland wind-sand disaster forms. Based on differences of features including landscape, water and soil resources and economic activity, etc., oasis in Ulan Buh Desert is divided, from the core to the edge, into three function areas, as the oasis eco-economic core area, oasis-desert ecological buffer area and desert ecological restoration area. Shifting sand intrusion and wind erosion are the main forms of oasis farmland disaster. In different function areas, sand sources and wind-sand disaster forms are different. Wind-sand disaster has the characteristics of generality, seasonality and anisotropy, etc.(2) Characteristics of oasis farmland wind-sand disaster variation with time and space. Experiments with surveyor's pole show that wind erosion in oasis farmland decreases from the oasis edge to the core, while in the same forest network, it increases from the edge of farmland to the core; as far as the time is concerned, wind erosion is weak in autumn and strong in spring. Movement rules of active dune and semi-fixed dune vary obviously with years and seasons, but their moving velocities are different. The main reason of oasis farmland sand-burying is the intrusion of shifting sand. The thickness of sand-burying and its consequence are different when sand sources are different.(3) Wind erosion and its control mechanism of oasis farmland. Field experiments on wind velocity and wind erosion depth show that different surface cover measures can lessen wind erosion. From strong to weak, the effect of controlling wind and fixing shifting sand is: in corn stem paving covering>corn stem piling covering>plastic film covering. Different methods of zero-tillage with stubble all have better effect than that of un-mulched farmland, and effects of method with long stubble>short stubble, dense stubble>sparsestubble. To irrigate and to mix sand with clay can lessen wind erosion by enhancing the unerodibility of soil particles.(4) Sand-fixing mechanism and shirting sand control effect of sand-barrier. Tunnel simulation and field experiments show that straw-checker sand-barrier, new material soil coagulant and geogrid sand-barrier control shifting sand with mechanism of blocking and fixing sand surface; the effect of controlling wind and fixing shifting sand and the antierodibility decreases with sand-barrier size, while sand-transporting quantity increases with it; the effect of new sand-barriers is better than that of damaged ones; damage forms and degrees are different at different dune parts. As far as soil coagulant of different densities are concerned, the 40% one has the strongest antierodibility, 20% the weakest and 30% relatively most practical. In geogrid, the thickness of accumulated sand increases with wind velocity, and decreases with porosity; geogrid has characteristics of easily moving, and can become taller to restore its function, which is the biggest advantage compared with other kinds of sand-barriers.(5) Wind-preventing and sand-controlling mechanism and effects of plants. The controlling wind and fixing shifting sand effect of farmland shelterbelt and wind-sand prevention and fixing forest varies with forest belt structure and height, and gets stronger successively as for networks; shrub forests have better effect than woody forest, shrubs with dense branches are better than those with sparse branches, and mixed forests with both trees and shrubs are better than pure forests; sand transport capacity of sand-fixing grass belt decreases with vegetation coverage; windbreak system composed of sand-fixing grass belt, wind-sand prevention and fixing forest and farml...