有充分的证据说明,雨滴的击溅打击作用是裸露地初期土壤侵蚀的主要动力(Young和Wiersmd,1673)、(Cham-pman,1948年),一般人们可能推测得出由森林林冠的存在可以减轻雨滴击力量从而保护了土壤.Champman在一块红松林(Red Pine)和邻近的一块开阔地进行雨滴大小分布的对比实验,对降雨强度为2—35mm/小时的降雨,开阔地雨滴直径和中值雨滴粒径的范围比林冠下雨滴 There is good evidence that raindrops are the main driving force behind bare soil erosion (Young and Wiersmd, 1673), (Cham-pman, 1948). One might speculate that the presence of forest canopies Champman conducted a comparative experiment on the size distribution of raindrops in a piece of red pine forest and an open area adjacent to it, and measured the raindrop diameter and median raindrop with a rainfall intensity of 2-35 mm / h, The particle size range raindrops below the canopy