THE GROWTH AND STATE OF SPRUCE UNDER THE CANOPY OF OXALIS BIRCH FORESTS IN THE SOUTHERN TAIGA OF THE EUROPEAN PART OF RUSSIA

The features of the growth of spruce ( Picea A. Dietr.) trees of various state under the canopy of southern taiga oxalis birch forests ( Betuletum oxalidosum ) are considered. The studies were carried out at the North Forest Experimental Station of the Institute of Forest Science, Russian Academy of Sciences, where a system of permanent trial plots (PTP) was established to study the succession processes in birch forests. At one of the PTP, all spruce trees were cut down as models. Preliminary assessment of their condition (healthy, weakened) was carried out. The shape and foliation of the crown, its length along the height of the tree were taken as evaluation criteria. Growth analysis was performed for trees over 60 years old (40 healthy, 33 weakened). Tree growth was characterized by the dynamics of the following indicators: height, stem cross-sectional area at a height of 0.1 and 1.3 m, stem volume, form factor, shape factor. In the course of a retrospective analysis of the growth of trees, it was found that weakened trees, in terms of the value of the biometric characteristics of the stem, are significantly inferior to healthy ones already in the first 10 years of life. At the age of 60, the height and stem volume of healthy trees are 1.5 and 3.1, respectively, higher than the values of these indicators in weakened specimens. Regardless of the condition of the trees, the maximum average periodic growth in height is observed at 40 years, and the equality of the average and average periodic growths in weakened trees is observed 5 years earlier (55 years) than in healthy ones. The maximum average periodic growth in cross-sectional area and stem volume in weakened trees occurs 5-10 years earlier than in healthy ones. Weakened trees are characterized by more full-boled and less tapering stems. At the age of 60 years, the productivity of healthy trees under the canopy of birch forests corresponds to IV, and weakened ones - to V growth class. The prospects of spruce trees under the canopy of birch forests are best assessed when the spruce reaches the age of 40 years.