摘要
本文是根据苗木冠部的几何结构和理论公式计算了北京地区夏半年(从春分至秋分)不同苗木行向以及不同叶面积指数下的日照时间,透光率和光分布。结果表明:1)光分布显著地受苗木行向的影响,苗木是东西行向时,比南北行向的光照时间长,最多可达7个多小时,透光率可大7.8％;2)苗木密度对透射条件的影响也很显著,当叶面积指数F_m=5时,透光量趋于稳定,且有利于苗木生长。上述理论分析的结果与田间所观测到的实际状况是一致的。
Based on the geometric structures of seedling crown, the authors the oritically calculated durations of sunshine, transmittivity and light distribution, for crops with different directions and different leaf area indexes, during the summer half year (from the Spring Equinox to the Autumnal Equinox) in Beijing area. The results show that 1) light distribution is obviously affected by the row direction,The seedlings in east-west rows have 7 hours more in daily sunshine and 7.8 percent larger in average transmivity than those in south-north rows; and 2 ) the effect of the density of seedlings on the transmission condition is also remarkable, when the leaf area index Fm equals 5 , the amount of transmission light tends to be steady and is optimal for the seedling, growth The theoritical analyses appear to be consistent conditions observed in field.
