报道了对华北平原农区杨粮间作复合生态系统林木理论遮荫面积和株行距的研究结果 ,给出了计算林木行内郁闭前后平均单株遮荫面积的方程 ;为保证南北行向的林木行内和行间均不造成重复遮荫 ,推导出了计算公式。在华北地区应用时 ,最小株距的计算可以采用 0 5× (冠幅 +冠长 ) ,最小行距可以采用2 9倍冠长 ;同时 ,要保证间作系统的长期性和稳定性 ,注意对杨树的修枝 ,并且当杨树成林时 ,5m× 2 5m是可以接受的株行距 This paper reports the results of theoretical research on shade theory and tree row spacing of composite grain-crop intercropping system in North China Plain, and gives the equation to calculate the average single-plant shade area before and after the closed canopy in the woodland row. Repeated shading was not caused between rows and rows, and the formula was deduced. When applied in North China, the minimum spacing can be calculated as 0 5 × (crown width + crown length) and the minimum spacing can be 29 times the crown length. At the same time, to ensure the long-term stability of the intercropping system, Of the pruning, and when the poplar forest, 5m × 25m is acceptable spacing