Study On Wind Breaking Effects With Belt Scheme Arbor Forest At Low Canopy Density

This paper study windbreak effects of belt pattern and random pattern arbor forest at low canopy density by wind tunnel experiment, and take a confirmatory test which was according to belt scheme sand-fixation forest of poplar and takeing elm wood land under same vegetation coverage as comparison to performe this study.Results are that:(1)It was found that random pattern, one-line-one-belt distribution pattern(OLOP) and two-line-one-belt distribution pattern (TLOP) both formed horizontal space flow field which was combined by the wind shadow and the wind speed acceleration area. (2)We divided the vertical space into three layers according to the different effect on vertical wind speeds, which were the tiny change layer (20 to 35 cm above the ground), the observably change layer (6to 12cm above the ground), and the stability of change layer (0.4 to 3cm above the ground). (3) when vegetation cover arrives at 0.2, the effect of reduce the horizontal space in OLOP and TLOP were identical, but there was a very significant difference in the effect between random and belt scheme patterns (P<0.0001).There was a very significant difference in random pattern , OLOP and TLOP when vegetation cover arrives at 0.25.(4) The effect of reduce the vertical space in random pattern , OLOP and TLOP were identical when vegetation cover arrives at 0.25. When vegetation cover arrives at0.2, the effect of reduce the vertical space in OLOP and TLOP were identical, but there was a very significant difference in the effect between random and belt scheme patterns (P<0.0001).(5)The soil surface roughness in TLOP was higher than OLOP, and the belt scheme patterns was higher than random scheme patterns. The soil surface roughness in belt scheme patterns was 8-10 times when vegetation cover arrives at 0.2 and 3-4 times when vegetation cover arrives at 0.25.(6) As the experiment in the field, the belt scheme arbor forest was higher than random cheme arbor forest about surface friction resistance and the function of hindrancing and changing the wind speed when analyse relative wind speed, soil surface roughness and Friction speed with vary wind speeds.