THE FEATURES OF SILVER BIRCH Betula verrucosa Ehrh. AND DOWNY BIRCH Betula pubescens Ehrh. SEED REGENERATION IN SUBTAIGA AND FOREST-STEPPE OF WESTERN SIBERIA
B. E. Chizhov1, R. I. Ivanova1, V. A. Shtol1, O. A. Kulyasova2
1All-Russian Research Institute of Silviculture and Mechanization of Forestry, Mekhanizatorov str., 5a, Building 2, Tyumen, 625017 Russian Federation
2State Agrarian University of Northern Zauralie, Roschinskoye Shosse str., 18, Tyumen, 625041 Russian Federation
Keywords: Западная Сибирь, лесостепь, береза, семенное размножение, гари, вырубки, пашни, Western Siberia, forest steppe, birch, seed reproduction, burns, logging lands, arable lands
Abstract
Article considers results of long-term studies of birch undergrowth in subtaiga subzone and forest-steppe zone of Western Siberia, the features of silver and downy birch seed regeneration under the canopy of parent stands, on logging, burned and abandoned arable lands, and hayfields. The distance of seed dispersal by wind, dynamics of accumulation of self-sown birch after continuous tillage and plough furrows is specified. It was found that seed regeneration under the birch stand canopy is hindered by drying of litter and root competition of the parent stand. A necessary condition for the germination of small seeds and the survival of weak shoots of birches is sufficient rainfall during the period of seed production and careful soil treatment, which provides removal of litter, total removal of herbaceous vegetation and soil reserve of weed seeds: continuous repeated plowing, bulldozing strips or shallow plow furrow with 0.7-1.0 m in width, with their additional cultivation. The most effective way of preparing land for seed regeneration of birch trees in arid steppe conditions is to transfer it under temporary cultivation of grain-crops, providing suppression of permanent weeds. Autumn plowing after harvest will provide annual readiness of the site for seed colonization of the birches. When there is an optimum combination of good seed harvest, rainy weather conditions, and appearance of mass self-sown birch, the land is excluded from the agricultural use. Prerequisites: the presence of seed productive walls of birch with preliminary removal of aspen and undesirable forms of birch. In spring of the next year an inventory is done of wintered self-sown birches, at least on 100 evenly spaced accounting plots. If the self-seeding dies, the site continues to be used by agriculture. Less reliable but acceptable is tillage by bulldozer stripes and furrows with 0.7-1.0 m in width, in a year of abundant seed production, before the start of mass seed fall.
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