English: 389.A medium-thick shelterbelt can reduce wind velocity by more than 10 percent to a distance of 20 times the tree height on the leeward side and three times the height to the windward.

• 中文:中等厚度的防风林在背风侧可在20倍于树高的距离而在迎风侧则在3倍于树高的距离上减小风速10%25以上。