摘要
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。
It is the fitst thing to be thought that when to begin thinning is suitable.The Dax-ing Anling climate and soil condition of the North region and south region is very different ,sothere are some difficulties to definite the suitable beginning time of the thinning. Accordiny to the result .of the Larix gmelini dividing region of the productivity of standsoil,we sort out the sample plot survey data. This essay analyse the changing raw of the diameter and the periodic increat of diameterbreast-high cross-sectional area. On the basis of the above analysing,we definite the suitablebeginning time of thinning.
