The causes and extension of dark coniferous forests die-off registered on f the northern macroslope of the Khamar-Daban Ridge from 2006–2009 are comprehensively investigated. The “wetwood” disease caused by bacteria Erwinia nimipressuralis Carter was recognized as a reason of forests die-off. The disease outbreak was triggered by the period of water shortages in the region. The approach implying landscape analysis was applied to assess the extent of damage to dark-coniferous forests. As a result of studies, the medium-scale map of geosystems was created. The map shows geosystem diversity at the facies level throughout the region. The forest stands were stratified into three levels according to the damage intensity (low, medium, and strong damage), and the size of the areas of damaged forest stands was calculated. The main areas of forests affected by the “wetwood” are concentrated within the eastern and western parts of the Khamar-Daban Ridge, and tend to occupy middle and upper bands of the mountain taiga belt. The Siberian cedar (Pinus sibirica) stands were the most suffered from the “wetwood”. The Siberian fir (Abies sibirica) stands were of a low damage level, while the Siberian spruce (Picea obovata) was not affected by the disease. The dramatic decreasing in the radial increment of the Siberian cedar stands during 2006–2009 years was discovered. Additionally, reduction of the spare nutrients amount in the Siberian cedar spore grains, as well as the decrease in the activity of germination was revealed. Besides, the negative signs of the Siberian cedar cones were observed, namely excessive resin amount combined with immaturity. These signs are typical when the “wetwood” is diagnosed. Abnormality in development of spores and cones is negatively influencing to the cedar seeds maturing, and finally impedes the forest regeneration.
|Affiliation of speaker||Сибирский институт физиологии и биохимии растений СО РАН|