在华北、中原平原地区营造杨树林带、林网,其规格、行数;树木定植后间伐与否,以及间伐的时间、强度等技术措施,是当前农田防护林经营工作应研究解决的重要内容。为探讨这些问题,我们对河北省新城县1976年栽植的北京杨林带连续三年进行了调查,并做了间伐试验。现将调查研究结果报告如下: In northern China and the Central Plains plain areas, poplar groves and forest webs are established, and their specifications and number of rows; technical measures such as thinning of the trees after planting, time and intensity of thinning are the important contents that should be studied and solved in the management of farmland shelterbelts. To explore these issues, we investigated the Yangling Belt planted in 1976 in Xincheng County, Hebei Province for three consecutive years and conducted a thinning test. Now report the findings as follows: