The increased mortality of Siberian stone pine and fir in taiga forests has been observed since the beginning of the 21st century. Krasnoyarsk scientists have found that the death of these moisture-loving dark conifers is associated with a deterioration in moisture supply observed under the conditions of climate warming. The intensification in the activity of insect pests, whose attacks are facilitated by the weakening of trees by water stress and periodic droughts, contributes to the increase in the mortality of dark conifers. According to forecasts, the increasing frequency and intensity of droughts may lead to the disappearance of dark conifers in the southern parts of their growing area. The research results are published in the journal Global Ecology and Biogeography.

The dark coniferous Siberian taiga, formed by Siberian cedar, fir and spruce, extends from the border with Mongolia to the Arctic Circle. Numerous international studies carried out in boreal forests indicate an increase in the mortality of conifers in recent decades. However, the exact reasons for the death of trees, its relationship with geographic and climatic features are not always known.

Scientists of the Federal Research Center "KSC SB RAS" used the materials of satellite monitoring, ground-based research and climatic data to identify the main causes of the drying out of Siberian cedar and fir. The researchers found that in the 21st century, the area of dead fir and cedar stands is 4% and 7.5%, respectively. The drying out of moisture-loving dark-coniferous stands, observed mainly in the southern part of their growing area, is associated with a moisture stress and attacks of insect pests affecting the weakened trees.

Analysis of the satellite images showed that the dried stands are located mainly in the south of Siberia, in low mountains less than 1000 m in height. Usually, they are located in the areas with an increased risk of water stress - southern, steep slopes. At the same time, in alpine forests, with sufficient moisture supply, climate warming has led to an increase in the annual growth and density of forest stands.

Interesting data were obtained in analyzing the annual growth of trees. It turns out that climate warming since the 1970s stimulated tree growth. However, a further increase in air temperature led to water stress and a decrease in growth, followed by drying out of some trees under the influence of droughts and pests. The main pest of fir is a bark beetle, Polygraphus proximus , whose mass development was not previously observed in the Siberian taiga. Cedar and fir stands are also damaged by their traditional enemy, Siberian silkworm, whose outbreaks have intensified in recent decades, and their impact zone has expanded due to climate warming.

“The results show that with the predicted increase in climate aridity, the growing area of Siberian cedar and fir in the southern low-altitude parts of Siberia will decrease with the likely replacement of these moisture-loving species with less demanding species, such as pine and larch,” says the Head of the Forest Monitoring Laboratory, Doctor of Biological Sciences, at the V.N. Sukachev Institute of Forest SB RAS, professor of SibFU, Vyacheslav Kharuk.

The research was supported by the Russian Foundation for Basic Research and Krasnoyarsk Regional Science Foundation.