UNDERGROWTH PHYTOMASS IN THE SECONDARY DECIDUOUS STANDS OF THE MIDDLE TAIGA

Abstract

The determination of organic matter reserves by forest phytocenoses is important in assessing biological produc-tivity of deciduous plantations formed at felling. As a rule, phytomass of the stand and soil cover is given when assess-ing forest productivity. This indicator is rarely determined for the undergrowth. The deciduous phytocenoses of the middle taiga, formed at the cutting of spruce of myrtillus type, have been studied. The undergrowth of the studied phy-tocenoses is represented by six species of woody plants: Salix caprea L., Sorbus aucuparia L., Rosa acicularis Lindl. and Lonicera pallasii Ledeb. Besides the mentioned species, Salix pentandra L. and S. philicifolia L are found in birch and spruce young growths. The method of “model trees” using allometric equations and the method of the “middle tree” for estimating the mass of individual species were used to determine the undergrowth phytomass. The specifics of the undergrowth phytomass dynamics in the studied after-cutting phytocenoses is associated with the overgrowing of felling by forest-forming and undergrowth species at the same time. It subsequently leads to competition between them. According to the studies in birch and spruce young forests, the undergrowth phytomass of decreased from 8.8 to 4.7 t/ha over 10 years; in aspen-birch stands - from 4.0 to 3.8. Throughout the entire studied period, fractions, accumulating organic matter (trunks and branches) for a long time, prevail in the undergrowth phytomass. The mass of leaves is 6-8% of the total undergrowth phytomass. The dynamics of the accumulation of organic matter by undergrowth is determined by biological characteristics of the species that form it, their abundance, natural thinning, and succession stage of the secondary stands.