Features of the Growth and Structure of Pine Wood in the Felling Area and Under the Canopy of a Tree Stand in the Conditions of the Republic of Karelia

Abstract

The intraspecific variability of the anatomical and hydraulic characteristics of xylem in the undergrowth in Scots pine (Pinus sylvestris L.) has been assessed during natural regeneration in the felling areas and under the canopy of a middle taiga blueberry pine forest in the conditions of the European North (Republic of Karelia). The influence of habitat conditions on the formation of structural elements of wood cells has been revealed. In felling areas under conditions of higher illumination, air and soil temperatures, the transition of pine undergrowth to the category of large with a height of more than 1.5 m occurs at the age of 6 years, whereas under the canopy of a mature stand the undergrowth reaches this category no earlier than 15 years. At the same time, in the 1st decade of growth under felling conditions, the growth of pine in diameter has been 4 times higher than that of pine under the canopy of a mature stand due to the formation of a larger number of rows of tracheids in the early and late zones. In addition, the pine undergrowth in the felling area has the highest potential hydraulic conductivity of the xylem, and, on the contrary, the lowest specific density of tracheids, the basic wood density and late wood content relative to the pine undergrowth under the canopy of the stand. The latter exhibited a significant decrease in the structural and functional characteristics of wood, with the exception of the thickness of the cell membranes of late tracheids. In the interanual dynamics, more stringent linear regression dependencies between the indices of early and late tracheids have been observed in pine undergrowth under the forest canopy. The results obtained indicate a greater correspondence of the environmental conditions in the felling area to the optimum for the growth and formation of wood of young pine trees relative to the conditions under the canopy of a mature blueberry pine forest. Inhibition of the growth activity of undergrowth under the canopy occurs due to high intraspecific competition from the dominant pine stand for light, moisture and soil nutrition.