FORMATION OF MIXED PINE-BIRCH STANDS WITH A SECOND STOREY OF SPRUCE UNDER THE INFLUENCE OF THINNING

Studies were carried out in pine-birch stands with a second storey of spruce in the north-taiga forest region of Arkhangelsk Oblast (Obozerskoe forestry district), which are formed under the influence of thinning. It’s specified, that thinning at the age of 40 years for taiga zone is unreasonably late stage of formation in such stands. The best option is the formation of forest stands by thinning in three steps. Then, at the age of 40, carry out a second thinning operation, leaving 1000 trees per ha of pine and birch in the first storey, and 2000 trees per ha of spruce in the second storey. At the age of 60, carry out the third stage of thinning, leaving 500-600 pine trees per ha in the upper storey, and 1000 spruce trees in the lower storey. Numbering of pine in the structure is regulating within 90 %. Based on the results obtained in the course of the study, the silvicultural effect of thinning on permanent trial plots is the formation of a spruce storey, which in the future can replace the forest stand after the final felling of the first storey. When thinning in mixed pine forests completed, the attitude to undergrowth is important. Thinning can undoubtedly increase the productivity of forests. The results of the studies will serve as the basis for the subsequent development of recommendations for managing mixed pine-birch stands with a second storey of spruce.