Growth of Spruce of Advance Regeneration after Birch Groves Felling in the Subzone of Southern Taiga of Russian Plain

Abstract

Introduction. Study of demutative processes in the industrial plantations of small-leaved species, and study of  growth dynamics of subordinate population of spruce are of current importance.   It is explained with the necessity to achieve the fastest recovery of spruce stands in the taiga region. Study of the influence of felling of small-leaved stands on the growth of preliminary generation of spruce is one of the aspects of such studies. The goal of the research is to study the influence of felling of upper canopy of birch on the growth of  age and  high level groups of subordinate population of spruce. Objects and methods. The growth of spruce of preliminary generation was studied under the canopy of  sorrel-myrtillus birch groves and after felling of these groves aged 55 at the  permanent samples of Northern forest  experimental station  of the Institute of Forest Science, Russian Academy of Sciences  (south taiga subzone – Rybinskiy district, Yaroslavl region). Growth course of 340 model trees of spruce was analyzed in detail in 20 years after felling. Results and discussion. Time response of spruce trees on the changes of environment,  arising from birch felling, is  mainly determined with the age and height of trees in the year of felling. The specifity of reaction  differs for the trees of different height groups. Apical growth is typical for the trees lower  2,0 m,  the trees with  2,1–6,0 m  height are characterized with apical  growth increase and growth  per cross-section area of  stem, the trees higher 6,0 m show only  growth  per cross-section area of   stem (apical growth is remained at the level of pre-felling period). Maximum apical growth is found to be in 10 years  after felling (trees ≤ 6,0 m), in 15 years after felling (trees > 6,0 m). Conclusion. As the factor, determining the perspectives for spruce growth after felling of birch, it is desirable to use the height of trees in the year of felling. Three groups of trees with different height (trees ≤ 2,0 m; trees 2,1–6,0 m; trees ˃ 6,0 m) are revealed in  accordance with the extent of response of trees to the changes of environment and dynamics of biometric data. Positive effect of all the spruce trees to birch felling is observed in the first five years. The duration of positive effect of felling on spruce growth is observed during 16–20 years. Crown density of spruce is twice increased, and intraspecific competition, determining considerable lowering of increment, becomes pointed during the period.