Home – Home – Jornals – Geography and Natural Resources 2019 number 4

Presented are the data from a comprehensive investigation into the causes and extent of dark coniferous forest dieback in geosystems of the northern macroslope of Khamar-Daban Range for the time interval 2006-2009. Forest dieback was caused by bacteria Erwinia nimipressuralis Carter. The disease outbreak was triggered by water scarcity in the region at that period. Land scape approach was used in assessing the magnitude of damage to dark-coniferous forests. The medium-scale map of geosystems was created for the northern macroslope of Khamar-Daban Range, showing the region’s geosystem diversity at the level of classes of facies. The ranking of forests was done according to three degrees of damage to tree stands (from strong to weak), and an assessment was made of the territory covered by them. The main areas of affected forests are concentrated in the eastern and western regions of Khamar-Daban where they occupy the middle and upper parts of the mountain-taiga belt. The Siberian stone pine stands suffered the most from the disease. Fir trees were less affected; in some areas, however, the damage to Siberian stone pine and fir stands is comparable. A dramatic decrease of the rate of radial increment in Siberian stone pine stands corresponds to the time interval 2006-2009. Furthermore, there occurred a decrease in nutrient content in pollen grains of Siberian stone pine and a decrease in of the rate of their germination as well as a negative transformation of Siberian stone pine cones in the form of their excessive resinosis and immaturity, which is one of the diagnostic features of bacterial dropsy. A disturbance to the development of pollen and pine cones negatively affects the ripening of Siberian stone pine seeds thus impeding forest regenera tion. However, a study of the state of the young growth in forest stands affected by bacterial dropsy bears witness to the gener ally satisfactory processes of dark-coniferous forest rehabilitation.