Thinning treatment is a necessary and complex forestry activity. The experimental results from plantations established 20-30 years ago and explains some concepts of the theory, practice, methods, and regime of thinning on the permanent sample plots of pine stands in Gatchinsky forestry of the Leningrad region were shown in this article. Choosing the right thinning method allows to optimize the yield, productivity and mortality of the stand. On the other hand, we observed improved merchantability of the stand, reduced time for forestation, and simplified thinning programs. Crown thinning is a less preferred method than bottom thinning, as it leads to a deterioration in the quality of trees and an increase in their mortality. The inexpediency of preliminary thinning of trees has been established. Tree thinning results in an improvement in the quality of the remaining stand, as nutrient utilization is greatly increased. Tree thinning must necessarily be combined with fertilization. Thinning without fertilization and fertilization without thinning show the worst results. In general, findings of this article can be used to improve approach of thinning treatment in the Leningrad or other regions in the North of Russian Federation.

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The process of wood debarking plays a crucial role in determining the price and quality of the final product. Hence, this work aims to elaborate on a theoretical basis for upgrading wood chips production technology. Consideration should be given to the influence of various debarking parameters when processing wood in barking drums. Such parameters as the number of wood collisions with each other and against a drum body, shear pressure, and others were chosen as equation coefficients to model the wood debarking time and knife sharpening angle. The treatment time is shown to depend on the number of collisions, the diameter of the log and indices that consider filling, the proportion of bark and the thickness, and wood hardness. It was established that the time required to debark the tree using knives is 1.5-3 times lower depending on the temperature of raw materials. Moreover, the process tends to be intensified with increasing knife sharpness.

The technical-and-economic efficiency of wood structures can be implemented by their longitudinal, transverse or combined reinforcement. Both metal and composites made of high-strength fibers (glass, carbon, aramid, basalt, etc) can be used as reinforcing materials. Schemes of reinforcement of wood and wood-glued structures by composite materials are described. The rational geometry of twisted composite reinforcement is proposed, which provides high adhesion to wood material. A method for determining the calculated resistance of a twisted bar to pulling out of wood is given. When calculating the holding force of the calculated pull-out resistance should take into account both the friction force at the contact boundary and the force of crushing the wood under the surfaces of the helical line. It makes possible to increase strength, rigidity, as well as the operational characteristics of wood structures, including load-bearing capacity, durability and reliability in chemically aggressive environments.

Due to economic and environmental factors, boiler houses are forced to switch to wood fuel, which is very popular in the modern world. The most practical way to supply them with wood fuel is to mobilize mobile chippers that can move between different boiler houses and save money on additional chipping equipment. This paper seeks to build a mathematical model to optimize the movement of a mobile chipper between multiple boiler houses and its operation during the heating season. The model was designed for long-term planning, and it relies on a simplex algorithm. It considers three crucial parameters: machine capacity, feedstock amount, and traveled distance, and is suitable for schedule modeling purposes in the presence of fewer than 12 nodes. The number of nodes can be higher after a heuristic rule is applied. The proposal can be help schedule the biomass feedstock development at the regional level and switch to the local types of fuel. In addition, it will reduce the cost of thermal energy and increase the volume of wood waste chipped.