应用田间实测资料,通过理论计算,揭示了农田立体林内可照时数,遮阴区域及强度的动态变化规律,为解决立体林内的光照问题提供了依据。结果表明:(1)毛白杨及山楂对麦田有不同程度的遮荫,山楂对麦田内可照时数的影响更甚;(2)一天中7点以前及16点以后林内无光照。中午荫影宽度最小,其一天平均遮蔽率为65％;(3)一天中,早、晚透光率较大,中午最小,山楂的透光率比毛白杨大。 The field measurement data are used to reveal the dynamic change law of illumination hours, shading area and intensity in farmland three-dimensional forest and provide the basis for solving the light problem in three-dimensional forest. The results showed that: (1) Populus tomentosa and hawthorn had different degrees of shading on the wheat field, hawthorn had more influence on the available hours in the wheat field; (2) There was no light in the forest before 7 o’clock and after 16 o’clock in the day. The shadow width at noon is the smallest, with an average masking rate of 65% a day. (3) The light transmittance of the middle of the day is higher in early morning and late afternoon than in white poplar.