AN EXPERIENCE IN CREATING MIXED FOREST CROPS IN MARI ZAVOLZH’E

The results of long-term experiments carried out on two stationary objects of forest plantations in 1976 and 1968 in different types of forest growing conditions of the Mari Trans-Volga region are presented. The plantations of the 1967, created in a dry forest, consisted only of pine Pinus L. and birch Betula L. trees in various proportions, and the second, created on loamy soils, is of three tree species (birch, spruce Picea A. Dietr. and pine). Pure pine plantations served as a control group. The productivity of the stand, its commodity composition and tax value were estimated by calculation in terms of the average diameter, height and number of trees according to our methodology. The relevance of research is driven by the need of improving measures to optimize the species composition of forests in order to preserve biological diversity, as well as reduce the frequency and intensity of fires. It is shown that in dry and fresh pine forests, pine-birch plantations demonstrate significantly worse stand productivity and especially tax value. Until the age of 10-15 years, the height of birch trees in them is higher than that of pines, but after 25-30 years, their position changes to the opposite. On sandy loam and loamy soils, birch suppresses from the composition of the stand not only light-loving pine, but even shade-tolerant spruce, significantly exceeding them in size. It is concluded that it is impractical to create mixed pine-birch and pine-spruce-birch crops in the conditions of the Mari Volga region due to the different demands of tree species on soil fertility, as well as differences in the speed of their growth and development. These plantations also do not fulfill the functions assigned to them for increasing the biological diversity and sustainability of the functioning of plantations, as well as to reduce their fire hazard.