CALORIFIC VALUE OF PINE WOOD IN CROPS OF THE NORTHERN TAIGA FOREST AREA
Calorific value of plants is an important characteristic for evaluation of material cycles and energy conversion in forest ecosystems, as well as a qualitative characteristic of plant raw materials as fuel. Wood biofuel is increasingly used in the production of thermal energy, in this regard, it is important to study the calorific value of wood, as well as the conditions for growing high-quality raw materials. The research purpose is to identify the dependence of the calorific value of pine wood in crops on its macroscopic structure, the assimilation apparatus characteristics, density and height of the stand. Small, medium, and large not damaged model trees without pathologies were selected on temporary sample plots. Cores from which were taken with an increment borer at a height of 1.3 m to measure radial growth on the semi-automatic complex Lintab-6 with an accuracy of ±0.01 mm. The calorific value of pine wood was determined in an absolutely dry state using an automated bomb calorimeter ABK-1V. To study the influence of the assimilating apparatus on the wood calorific value, needles of all ages were selected from the middle branch of the model tree crown. Cross sections were prepared from the middle part of a needle using a sledge microtome MS-2. Histological elements of a needle were measured by the Axio Scope.A1 microscope using the IMAGE-PRO INSIGHT 8.0 software. The average heat capacity of pine wood in heath-lichen pine forests is (20 731±133) J/g; in cowberry pine forests - (20 618±141) J/g; in bilberry pine forests - (20 513±104) J/g at a stand density from 1160 to 3806 pcs/ha. The highest pine wood heat capacity is found in heath-lichen pine forests with the density of stand 5021 pcs/ha. The increased pine wood heat capacity in pine forests with high stand density is due to a reduction in the number of needles on the branch (r = -0.75) and an increase in the diameter of resin channels (r = - 0.88). The influence of the average stand height and the annual layer structure on the calorific value of pine wood was found.