Study On Benefit Evaluation And Patterns Of Wind Erosion Protective System In Ulan Buh Desert Oasis

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 and laboratory experiment. The main research result is:(1) From outside to inside, Wind erosion protective system in Ulan buh desert is made up of three layers: sand-fixing grass belt, wind-sand prevention and fixing forest, and farmland shelterbelt.(2) Wind velocity of different farmland shelterbelt was observed; results showed that defending effect varies with forest belt structure, height and porosity. Wind defending effect of sparse structure shelterbelt is the best, which is 32.2%, porous structure takes second place, 23%, while, ventilation structure is the worst, 13.2%. Shelterbelt with the porosity of 40~50% has the best wind defending effect.With the increasing of porosity total porosity, the defending effect decreased remarkably. So the structure should be sparse with the porosity of 30~50%, and the porosity of forest canopy should be 30~50%, the porosity of trunk, 50%. Moreover, shelterbelt can reduce the sand-transporting quantity, and the fall rate after the forest is more than the one before the forest. The sand-transporting quantity after the mixed-forest decreased to zero.(3) Study on the wind defending effect about five shrub communities showed that the wind defending effect of Haloxylon ammondendron and Hedysarum scaparium is better than other, which is respectively 62.4% and 53.8%, its defending effect is related to the density, coverage and height. However, wind velocity in the hight of 0.3m in shrub of Hedysarum laeve reduced by 77.1% because it has more divarication. Under the same wind velocity, sand-transporting quantities in five shrubs are all less than the one in sandy land, in the shrub of Hedysarum laeve it decreased the most, reach to 98.5%, Haloxylon ammondendron is the second one, 97.5%, pyramidalis Bunge is the last one ,which is 39.6%. The distribution of dust deposition show that the one on the height of 2 meter is more than the one on the height of 5 meter, and the one in the center of the forest is more than the one in other places. The average dust deposition amount in the hight of 2m in the center of the forest is 22.8g/m~2*1d, in the hight of 5m, it is 19.3g/m~2*1d, and in other places, it is 3.14～14.4 g/m~2*1d in the hight of 2m, , and 1.87～8.36g/m~2*1d in the hight of 5m(4) Study on sand-trapping efficiency of sand-fixing grass belt show that natural shrub have the...