| The matter of preventing wind erosion about the vegetation has always been a focus of attention, but the past research mostly centered on the area about the effect of vegetation coverage, the mechanism of planting disposition to prevent soil wind erosion hasn't been researched systemically and deeply. For a long time, many researchers all confirm when the vegetation coverage is low, it can't completely keep drifting sand in place, however, in arid and semi-arid region, limited by water condition, so the vegetation coverage isn't very high. Through rational distribution of plants, it can be gotten down, and effect of controlling soil wind erosion won't be decreased. The paper takes the common species in Mu Us sandland — Artemisia sphaerocephala,Caragana intermedia,Hedysarum fruticosum var mongolicum,Populs alba var Pyramidalisas,Populus simonii as research subjects, through the research on the aspects of wind field distribution and wind energy change, analysis the mechanism of planting disposition to prevent soil wind erosion based on aerodynamics principle, try to find several rational distribution of plants, in order to provide reference basis for vegetation construction in Mu Us sandland. The conclusion is:(1) From the effect of wind velocity attenuation on leeward side, Artemisia sphaerocephala>Caragana intermedia>Hedysarum fruticosum var mongolicum, and decreased rapidly between 1.5～2.0 meters on leeward side. Hence it is not difficult to conclude that the protection distance of Artemisia sphaerocephala is 7H and the others are 5H.The sediment discharge of Artemisia sphaerocephala is in accordance with the velocity changes, sand-shifting control of 1H on leeward side is the most remarkable. The sediment discharge of each point mostly converged in the range of 0～ 20 centimeter height and it is accounted for over 95 % in average.(2) The effect of individual arbor for controlling wind erosion is as same as the individual arbustum above the part of tree crow, and wind velocity will be down on leeward side. However, when wind gets across the stem of arbor, the velocity will be 1~2 times larger than incoming flow. So the individual arbor is easy to eroded, a certain scale of high forest could have better protective effect.(3) The wind velocity profile of Artemisia sphaerocephala with uniformity model, stochastic model and banding collocate all follow one-variable linear regression, and velocity increased with height. The decrease range is largest inside brush with banding collocate and the surface roughness is stablest; the stochastic model is least and the surface roughness changes sharply; the uniformity model is in the middle. So the effect of banding collocates for controlling wind erosion is best and optimal band width is 5 meters. (4) The lowest wind velocity of high forest appears in 3～7H from leeward side, and the protection distance is 7H.The protective effect of patch forest is better than single forest belt, but when forest belts are put up into belt net with the protection distance, they will be better than patch forest. So in order to prevent and reduce the soil wild erosion, there should develop the forest belts with belt distance between 150-200 meters.(5) The protective effect of high forest belt is better than banding collocate shrub forest, and they are suitable on the sandy farmland of better water conditions. In lower water area, because of restricted by water condition, banding collocate shrub forest is most appropriate.
|
PDF Full Text Request