Assessment of the silvicultural efficiency of thinning cuttings in the northern taiga forest region

The article presents the 13-th years observations results on permanent sample plots established in the Obozersky forestry district of the Arkhangelsk region. The objects of observation are mixed stands that have middle-aged stands thinning in the northern taiga region. The study focuses on mixed stands subjected to thinning operations in the northern taiga region. The research aims to analyze changes in mensuration parameters, stability, and productivity of mixed bilberry pine stands in the northern taiga following thinning operations. The current forest structure in Arkhangelsk region and the European North of Russia is characterized by a significant predominance of secondary forests formed under long-term management activities. These stands exhibit complex age and species differentiation, highlighting the particular relevance of developing science-based approaches for managing middle-aged stands. Improving forest management efficiency under these conditions holds important socio-economic significance as it simultaneously addresses sustainable forest use and ensures the raw material base for the timber industry. For the monitoring organization and implementation, 6 second-generation stands were surveyed. Repeated inventories allowed assessment of stand structure and timber quality. To evaluate silvicultural effectiveness, changes in stand mensuration parameters were analyzed, reflecting tree growth and development dynamics under new environmental conditions. The sample plots were established to monitor changes following thinning operations using forest mensuration methods. Each plot assessed quantitative and qualitative stand parameters (species composition, mean height and diameter, age, site class, relative and absolute density, growing stock, timber quality, physiological condition), as well as understory and shrub layer characteristics. Monitoring was conducted through repeated measurements at 8 and 13 years post-treatment. The long-term study revealed that the forest community maintained its stability, evidenced by preserved stand productivity and stable dynamics of mensuration parameters. Observed stem differentiation reflects natural competitive interactions between species. Analysis of mensuration characteristics demonstrated stand adaptation to new environmental conditions while maintaining key ecosystem functions. On five sample plots, a one-unit decrease in Scots pine (Pinus sylvestris L.) proportion was recorded, reflecting characteristic species composition transformation dynamics following selective thinning in mixed pine stands. Stands showed significant interspecies competition effects, leading to reduced pine proportion and vertical structure changes that stimulate multi-layered stand formation and productivity enhancement. Continued analysis of stand growth trends after thinning interventions will facilitate the formulation of guidelines regarding treatment frequency and intensity, with the goal of sustaining productivity within mixed stands.