确定首次抚育间伐的开始期是进行森林抚育间伐生产时首先要解决的问题。内蒙古大兴安岭林区南北气候及土壤条件差异较大，为科学地确定不同生产力区的抚育间伐开始期造成了一定困难，本文根据兴安落叶松不同生产力区，调查整理了有关固定标准地材料，分析林木胸径与胸高断面积连年生长量的变化，以此为依据来确定抚育间伐的开始期。 Determining the beginning of the first tending of thinning is the first issue to be solved in the process of thinning in forest tending. The difference of climate and soil conditions between the north and the south of Daxinganling in Inner Mongolia is quite different, which makes it difficult to scientifically determine the initial period of tending and thinning in different productive areas. Based on the different productivity areas of Larix gmelinii, Changes in DBH and DBH area, as the basis to determine the beginning of tending thinning.