Carbon stock in grass cover of forests with different severity of stem pest-related stand weakening in the southern taiga zone of Western Siberia

The paper addresses the study of dark coniferous forests of the southern taiga, which were analyzed with regard to severity of stand weakening caused by stem pests, up to stand death. To assess the carbon stock of grass cover, the mass fraction of carbon in grass species and the aboveground mass of grass were measured. The carbon stock of grass cover was shown to vary during the change in its main microgroups caused by stand weakening. The carbon content in grass species abundant in different grass microgroups exhibits a narrow range of variation of 33.4–44.7 %, with an average of 41.1±0.9 %. The amount of carbon stored in the grass cover of dark coniferous forests in uplands ranges from 16.2 to 32.9 gC/m2. It was revealed that in weakened stands, the grass cover stores 2–5 fold more carbon due to an increase in grass biomass. Considering that most of the grass carbon released to the atmosphere within a year, the efficiency of carbon sink in forest areas with dead stands becomes lower, despite an increase in grass mass, compared to forest areas where the stands are not damaged by stem pests.