The Study On Scheme And Windbreak Effects Of Artemisia. Ordosica Shrub Of MuUs Sandy Land

Conventional studies think that when vegetation cover arrives at 40%, sand land is fixed. When vegetation cover is from 20% to 40%, sand land is semi-flowing and semi-fixing. However, in practice it has been found that at low vegetation coverage, the horizontal distribution pattern of shrubs can have marked effects on fixation of shifting sands. For making clear that this phenomenon bring physical mechanism, this paper study windbreak effects and controlling the sand blown flow of low cover Artemisia. ordosica shrubs by field, Wind tunnel experiment and indoor analysis.Results of windbreak: (1) when cover was at about 20%, the belt scheme A. ordosica shrub was more 20.6% effective for wind breaking than the randomly distributed shrub. This shows that when vegetation cover is sparse, the belt scheme is the most effective plantation in the windbreak effect. (2) For belt scheme A. ordosica shrub, consecutive whole belt combination has obvious accumulating effect on reducing wind speed. (3) Belt pattern shape regular fluctuate flow field structure. Wider belt pattern shape more areas of reducing and ncreasing wind speed. Because distributing character of shrubs and hypsography, random pattern shape very complicated flow field structure that is combined several wind shadow zone with several increasing wind speed. Equal distance between plant and plant and row and row pattern lie between belt pattern and random pattern.Results of wind erosion simulation experiment: (1) when wind speed is 10m/s, wind erosion do not appear with belt scheme, three multiplied by three and random scheme appear wind erosion in 8min and 3min, respectively. (2) When wind speed is 15m/s, belt scheme appear light wind erosion and accumulating sand and engender steady"concave"sand surface after 30min. Most wind erosion and accumulating sand are 2.0 cmand 2.7 cm, respectively. Moreover, belt scheme do not engender the sand blown flow after 30min. However, three multiplied by three and random scheme blow 65.57% and 66.96% sand after 30min, respectively. (3) Wind erosion of three multiplied by three scheme mostly appear in spacing sand surface of shrubs. Wind erosion of random scheme mostly appear in large spacing sand surface of shrubs. Moreover, accumulating sand of random scheme mostly appear in collecting part of shrubs. Thus random scheme engender very complicated shape of sand surface.