State, ecological-coenotic characteristics, and prospects of the silver birch (Betula pendula Roth, Betulaceae, Dicotyledones) forest cultures in steppe afforestation

摘要

In the summer of 2010, thermal damages to birch in cultures reached 4.2-4.8 points according to the authors' five-point scale. In 2011, the stands of birch trees were weakened to variable degrees, but some healthy stands remained. High-density forest massifs and birch forest belts are more drought-resistant. The grass cover is weakly developed therein. Thinned birch cultures become overgrown with herbs and die out after droughts. The root exudates of shrubs depress the intensity of photosynthesis of steppe plants by 10-25%. In vegetation experiments, various species of shrubs stimulate or slow down the growth of shoots and roots and the intensity of photosynthesis of the birch by 10-30%, on average. It is recommended to cultivate birch trees in forest belts using shrubby borders with high allelopathic activity for biological defense of the soil from overgrowth with weedy and steppe plants.