EFFECTS OF BIRCH FOREST PARCEL STRUCTURE ON SPATIAL HETEROGENEITY OF GROUND COVER IN SOUTHERN TAIGA

Abstract

Introduction. Studying the structure of forest phytocenosis on the parcel level helps to forecast their development, to assess possibilities of successful tree species regeneration and quality of understory. In comparison with soil, the ground cover represents the current type of a biocoenosis and a moisture regime in a greater extent, being a sensitive indicator of the contemporary changes in the biosphere. The paper aims to is to study the dynamics of the birch forest parcel structure in connection with natural regeneration of spruce under the birch canopy, to analyze the effect of phytocenosis parcel structure on the forest litter. Materials and methods. The investigations were performed in the southern taiga by the Northern Forest Experimental Station of the Institute of Forest Science, RAS, (Rybinsk district, the Yaroslavl region). The works were done on 17 permanent inventory plots 625-3300 sq.m. in size, the predominant forest types were sorrel family or bilberry birch forests. The first layer of secondary stands consists mostly of birch trees (70-100 %) (BetulapendulaRoth.) and partially of aspen trees (up to 30 %) (PopulustremulaL.) The age of birch forests on the inventory plots is 40-115 y.o., canopy density is 0.8-1.0, Yield Class Ia. The spruce population regenerates under the birch canopy (PiceaabiesL.) Conclusion. The ground cover is closely related to the spruce crown density, the crown density relates to spruce normality and the ratio of utilization of parcel's aboveground space by trees. The two-horizon ground cover is formed, as a rule, in parcels with single spruces. The increase of the spruce portion in the parcel volume results in three-horizon ground cover and the increase in its deposit. The ground cover found next to spruce trunks within a parcel is maximum large. The variety of the ground cover in sorrow birch forests and bilberry birch forests are significantly different.