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俗语说“寸草挡丈风”。农田防护林网,能够直接削弱风速,改变气流的交换,对林网内的农田小气候有深刻的影响,可为农作物的生长、发育创造良好的环境条件。据观测:林带可降低风速百分之二十至五十左右,有效防风距离为林带树高的三十倍(其中林带迎风面为五倍,背风面为二十五倍),风速愈大,这种防护作用愈显著。由于风速的降低,在风沙地区,可以防止风蚀表土、沙埋粮田和幼苗等现象,有明显的护土作用,土壤中水分的蒸发量也相对减少百分之十五至二十五。同时,由于林带阻碍了气流的垂直交换,使近地面的空间湿
As the saying goes “inch grass block husband wind.” Farmland shelterbelts can directly reduce the wind speed, change the exchange of air currents and have a profound impact on the farmland microclimate in the forest network, which can create good environmental conditions for the growth and development of crops. It is observed that the forest belt can reduce the wind speed by about 20% to 50% and the effective windbreak distance is thirty times of the forest tree height (in which the windward side of the forest zone is five times and the leeward side is twenty-five times) The more significant this protective effect. Due to the decrease of wind speed, wind erosion area can prevent the erosion of topsoil, sand and grain fields and seedlings. Clearly, the effect of soil conservation is also to reduce the evaporation of moisture in the soil by 15% -25%. At the same time, the space near the ground is wet because the belt prevents the vertical exchange of air currents